It is not possible for the current verifier to track ALU32 and JMP ops
correctly. This can result in the verifier aborting with errors even though
the program should be verifiable. BPF codes that hit this can work around
it by changin int variables to 64-bit types, marking variables volatile,
etc. But this is all very ugly so it would be better to avoid these tricks.

But, the main reason to address this now is do_refine_retval_range() was
assuming return values could not be negative. Once we fixed this code that
was previously working will no longer work. See do_refine_retval_range()
patch for details. And we don't want to suddenly cause programs that used
to work to fail.

The simplest example code snippet that illustrates the problem is likely
this,

 53: w8 = w0                    // r8 <- [0, S32_MAX],
                                // w8 <- [-S32_MIN, X]
 54: w8 <s 0                    // r8 <- [0, U32_MAX]
                                // w8 <- [0, X]

The expected 64-bit and 32-bit bounds after each line are shown on the
right. The current issue is without the w* bounds we are forced to use
the worst case bound of [0, U32_MAX]. To resolve this type of case,
jmp32 creating divergent 32-bit bounds from 64-bit bounds, we add explicit
32-bit register bounds s32_{min|max}_value and u32_{min|max}_value. Then
from branch_taken logic creating new bounds we can track 32-bit bounds
explicitly.

The next case we observed is ALU ops after the jmp32,

 53: w8 = w0                    // r8 <- [0, S32_MAX],
                                // w8 <- [-S32_MIN, X]
 54: w8 <s 0                    // r8 <- [0, U32_MAX]
                                // w8 <- [0, X]
 55: w8 += 1                    // r8 <- [0, U32_MAX+1]
                                // w8 <- [0, X+1]

In order to keep the bounds accurate at this point we also need to track
ALU32 ops. To do this we add explicit ALU32 logic for each of the ALU
ops, mov, add, sub, etc.

Finally there is a question of how and when to merge bounds. The cases
enumerate here,

1. MOV ALU32   - zext 32-bit -> 64-bit
2. MOV ALU64   - copy 64-bit -> 32-bit
3. op  ALU32   - zext 32-bit -> 64-bit
4. op  ALU64   - n/a
5. jmp ALU32   - 64-bit: var32_off | upper_32_bits(var64_off)
6. jmp ALU64   - 32-bit: (>> (<< var64_off))

Details for each case,

For "MOV ALU32" BPF arch zero extends so we simply copy the bounds
from 32-bit into 64-bit ensuring we truncate var_off and 64-bit
bounds correctly. See zext_32_to_64.

For "MOV ALU64" copy all bounds including 32-bit into new register. If
the src register had 32-bit bounds the dst register will as well.

For "op ALU32" zero extend 32-bit into 64-bit the same as move,
see zext_32_to_64.

For "op ALU64" calculate both 32-bit and 64-bit bounds no merging
is done here. Except we have a special case. When RSH or ARSH is
done we can't simply ignore shifting bits from 64-bit reg into the
32-bit subreg. So currently just push bounds from 64-bit into 32-bit.
This will be correct in the sense that they will represent a valid
state of the register. However we could lose some accuracy if an
ARSH is following a jmp32 operation. We can handle this special
case in a follow up series.

For "jmp ALU32" mark 64-bit reg unknown and recalculate 64-bit bounds
from tnum by setting var_off to ((<<(>>var_off)) | var32_off). We
special case if 64-bit bounds has zero'd upper 32bits at which point
we can simply copy 32-bit bounds into 64-bit register. This catches
a common compiler trick where upper 32-bits are zeroed and then
32-bit ops are used followed by a 64-bit compare or 64-bit op on
a pointer. See __reg_combine_64_into_32().

For "jmp ALU64" cast the bounds of the 64bit to their 32-bit
counterpart. For example s32_min_value = (s32)reg->smin_value. For
tnum use only the lower 32bits via, (>>(<<var_off)). See
__reg_combine_64_into_32().

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/158560419880.10843.11448220440809118343.stgit@john-Precision-5820-Tower

do_refine_retval_range() is called to refine return values from specified
helpers, probe_read_str and get_stack at the moment, the reasoning is
because both have a max value as part of their input arguments and
because the helper ensure the return value will not be larger than this
we can set smax values of the return register, r0.

However, the return value is a signed integer so setting umax is incorrect
It leads to further confusion when the do_refine_retval_range() then calls,
__reg_deduce_bounds() which will see a umax value as meaning the value is
unsigned and then assuming it is unsigned set the smin = umin which in this
case results in 'smin = 0' and an 'smax = X' where X is the input argument
from the helper call.

Here are the comments from _reg_deduce_bounds() on why this would be safe
to do.

 /* Learn sign from unsigned bounds.  Signed bounds cross the sign
  * boundary, so we must be careful.
  */
 if ((s64)reg->umax_value >= 0) {
	/* Positive.  We can't learn anything from the smin, but smax
	 * is positive, hence safe.
	 */
	reg->smin_value = reg->umin_value;
	reg->smax_value = reg->umax_value = min_t(u64, reg->smax_value,
						  reg->umax_value);

But now we incorrectly have a return value with type int with the
signed bounds (0,X). Suppose the return value is negative, which is
possible the we have the verifier and reality out of sync. Among other
things this may result in any error handling code being falsely detected
as dead-code and removed. For instance the example below shows using
bpf_probe_read_str() causes the error path to be identified as dead
code and removed.

>From the 'llvm-object -S' dump,

 r2 = 100
 call 45
 if r0 s< 0 goto +4
 r4 = *(u32 *)(r7 + 0)

But from dump xlate

  (b7) r2 = 100
  (85) call bpf_probe_read_compat_str#-96768
  (61) r4 = *(u32 *)(r7 +0)  <-- dropped if goto

Due to verifier state after call being

 R0=inv(id=0,umax_value=100,var_off=(0x0; 0x7f))

To fix omit setting the umax value because its not safe. The only
actual bounds we know is the smax. This results in the correct bounds
(SMIN, X) where X is the max length from the helper. After this the
new verifier state looks like the following after call 45.

R0=inv(id=0,smax_value=100)

Then xlated version no longer removed dead code giving the expected
result,

  (b7) r2 = 100
  (85) call bpf_probe_read_compat_str#-96768
  (c5) if r0 s< 0x0 goto pc+4
  (61) r4 = *(u32 *)(r7 +0)

Note, bpf_probe_read_* calls are root only so we wont hit this case
with non-root bpf users.

v3: comment had some documentation about meta set to null case which
is not relevant here and confusing to include in the comment.

v2 note: In original version we set msize_smax_value from check_func_arg()
and propagated this into smax of retval. The logic was smax is the bound
on the retval we set and because the type in the helper is ARG_CONST_SIZE
we know that the reg is a positive tnum_const() so umax=smax. Alexei
pointed out though this is a bit odd to read because the register in
check_func_arg() has a C type of u32 and the umax bound would be the
normally relavent bound here. Pulling in extra knowledge about future
checks makes reading the code a bit tricky. Further having a signed
meta data that can only ever be positive is also a bit odd. So dropped
the msize_smax_value metadata and made it a u64 msize_max_value to
indicate its unsigned. And additionally save bound from umax value in
check_arg_funcs which is the same as smax due to as noted above tnumx_cont
and negative check but reads better. By my analysis nothing functionally
changes in v2 but it does get easier to read so that is win.

Fixes: 849fa506

 ("bpf/verifier: refine retval R0 state for bpf_get_stack helper")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/158560417900.10843.14351995140624628941.stgit@john-Precision-5820-Tower

LSM and tracing programs share their helpers with bpf_tracing_func_proto
which is only defined (in bpf_trace.c) when BPF_EVENTS is enabled.

Instead of adding __weak symbol, make BPF_LSM depend on BPF_EVENTS so
that both tracing and LSM programs can actually share helpers.

Fixes: fc611f47

 ("bpf: Introduce BPF_PROG_TYPE_LSM")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200330204059.13024-1-kpsingh@chromium.org

Joe Stringer says:

====================
Introduce a new helper that allows assigning a previously-found socket
to the skb as the packet is received towards the stack, to cause the
stack to guide the packet towards that socket subject to local routing
configuration. The intention is to support TProxy use cases more
directly from eBPF programs attached at TC ingress, to simplify and
streamline Linux stack configuration in scale environments with Cilium.

Normally in ip{,6}_rcv_core(), the skb will be orphaned, dropping any
existing socket reference associated with the skb. Existing tproxy
implementations in netfilter get around this restriction by running the
tproxy logic after ip_rcv_core() in the PREROUTING table. However, this
is not an option for TC-based logic (including eBPF programs attached at
TC ingress).

This series introduces the BPF helper bpf_sk_assign() to associate the
socket with the skb on the ingress path as the packet is passed up the
stack. The initial patch in the series simply takes a reference on the
socket to ensure safety, but later patches relax this for listen
sockets.

To ensure delivery to the relevant socket, we still consult the routing
table, for full examples of how to configure see the tests in patch #5;
the simplest form of the route would look like this:

  $ ip route add local default dev lo

This series is laid out as follows:
* Patch 1 extends the eBPF API to add sk_assign() and defines a new
  socket free function to allow the later paths to understand when the
  socket associated with the skb should be kept through receive.
* Patches 2-3 optimize the receive path to avoid taking a reference on
  listener sockets during receive.
* Patches 4-5 extends the selftests with examples of the new
  functionality and validation of correct behaviour.

Changes since v4:
* Fix build with CONFIG_INET disabled
* Rebase

Changes since v3:
* Use sock_gen_put() directly instead of sock_edemux() from sock_pfree()
* Commit message wording fixups
* Add acks from Martin, Lorenz
* Rebase

Changes since v2:
* Add selftests for UDP socket redirection
* Drop the early demux optimization patch (defer for more testing)
* Fix check for orphaning after TC act return
* Tidy up the tests to clean up properly and be less noisy.

Changes since v1:
* Replace the metadata_dst approach with using the skb->destructor to
  determine whether the socket has been prefetched. This is much
  simpler.
* Avoid taking a reference on listener sockets during receive
* Restrict assigning sockets across namespaces
* Restrict assigning SO_REUSEPORT sockets
* Fix cookie usage for socket dst check
* Rebase the tests against test_progs infrastructure
* Tidy up commit messages
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Add support for testing UDP sk_assign to the existing tests.

Signed-off-by: Joe Stringer <joe@wand.net.nz>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Lorenz Bauer <lmb@cloudflare.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200329225342.16317-6-joe@wand.net.nz

Attach a tc direct-action classifier to lo in a fresh network
namespace, and rewrite all connection attempts to localhost:4321
to localhost:1234 (for port tests) and connections to unreachable
IPv4/IPv6 IPs to the local socket (for address tests). Includes
implementations for both TCP and UDP.

Keep in mind that both client to server and server to client traffic
passes the classifier.

Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Joe Stringer <joe@wand.net.nz>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200329225342.16317-5-joe@wand.net.nz

Co-authored-by: Joe Stringer <joe@wand.net.nz>

Avoid taking a reference on listen sockets by checking the socket type
in the sk_assign and in the corresponding skb_steal_sock() code in the
the transport layer, and by ensuring that the prefetch free (sock_pfree)
function uses the same logic to check whether the socket is refcounted.

Suggested-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Joe Stringer <joe@wand.net.nz>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200329225342.16317-4-joe@wand.net.nz

Refactor the UDP/TCP handlers slightly to allow skb_steal_sock() to make
the determination of whether the socket is reference counted in the case
where it is prefetched by earlier logic such as early_demux.

Signed-off-by: Joe Stringer <joe@wand.net.nz>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200329225342.16317-3-joe@wand.net.nz

Add support for TPROXY via a new bpf helper, bpf_sk_assign().

This helper requires the BPF program to discover the socket via a call
to bpf_sk*_lookup_*(), then pass this socket to the new helper. The
helper takes its own reference to the socket in addition to any existing
reference that may or may not currently be obtained for the duration of
BPF processing. For the destination socket to receive the traffic, the
traffic must be routed towards that socket via local route. The
simplest example route is below, but in practice you may want to route
traffic more narrowly (eg by CIDR):

  $ ip route add local default dev lo

This patch avoids trying to introduce an extra bit into the skb->sk, as
that would require more invasive changes to all code interacting with
the socket to ensure that the bit is handled correctly, such as all
error-handling cases along the path from the helper in BPF through to
the orphan path in the input. Instead, we opt to use the destructor
variable to switch on the prefetch of the socket.

Signed-off-by: Joe Stringer <joe@wand.net.nz>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200329225342.16317-2-joe@wand.net.nz

We've added John Fastabend to our weekly BPF patch review rotation over
last months now where he provided excellent and timely feedback on BPF
patches. Therefore, add him to the BPF core reviewer team to the MAINTAINERS
file to reflect that.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/0e9a74933b3f21f4c5b5a3bc7f8e900b39805639.1585556231.git.daniel@iogearbox.net

The bounds checking for the arguments accessed in the BPF program breaks
when the expected_attach_type is not BPF_TRACE_FEXIT, BPF_LSM_MAC or
BPF_MODIFY_RETURN resulting in no check being done for the default case
(the programs which do not receive the return value of the attached
function in its arguments) when the index of the argument being accessed
is equal to the number of arguments (nr_args).

This was a result of a misplaced "else if" block  introduced by the
Commit 6ba43b76 ("bpf: Attachment verification for
BPF_MODIFY_RETURN")

Fixes: 6ba43b76

 ("bpf: Attachment verification for BPF_MODIFY_RETURN")
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200330144246.338-1-kpsingh@chromium.org

reg_set_min_max_inv() contains exactly the same logic as reg_set_min_max(),
just flipped around. While this makes sense in a cBPF verifier (where ALU
operations are not symmetric), it does not make sense for eBPF.

Replace reg_set_min_max_inv() with a helper that flips the opcode around,
then lets reg_set_min_max() do the complicated work.

Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200330160324.15259-4-daniel@iogearbox.net

The BPF verifier tried to track values based on 32-bit comparisons by
(ab)using the tnum state via 581738a6 ("bpf: Provide better register
bounds after jmp32 instructions"). The idea is that after a check like
this:

    if ((u32)r0 > 3)
      exit

We can't meaningfully constrain the arithmetic-range-based tracking, but
we can update the tnum state to (value=0,mask=0xffff'ffff'0000'0003).
However, the implementation from 581738a6 didn't compute the tnum
constraint based on the fixed operand, but instead derives it from the
arithmetic-range-based tracking. This means that after the following
sequence of operations:

    if (r0 >= 0x1'0000'0001)
      exit
    if ((u32)r0 > 7)
      exit

The verifier assumed that the lower half of r0 is in the range (0, 0)
and apply the tnum constraint (value=0,mask=0xffff'ffff'0000'0000) thus
causing the overall tnum to be (value=0,mask=0x1'0000'0000), which was
incorrect. Provide a fixed implementation.

Fixes: 581738a6

 ("bpf: Provide better register bounds after jmp32 instructions")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200330160324.15259-3-daniel@iogearbox.net

Anatoly has been fuzzing with kBdysch harness and reported a hang in
one of the outcomes:

  0: (b7) r0 = 808464432
  1: (7f) r0 >>= r0
  2: (14) w0 -= 808464432
  3: (07) r0 += 808464432
  4: (b7) r1 = 808464432
  5: (de) if w1 s<= w0 goto pc+0
   R0_w=invP(id=0,umin_value=808464432,umax_value=5103431727,var_off=(0x30303020;0x10000001f)) R1_w=invP808464432 R10=fp0
  6: (07) r0 += -2144337872
  7: (14) w0 -= -1607454672
  8: (25) if r0 > 0x30303030 goto pc+0
   R0_w=invP(id=0,umin_value=271581184,umax_value=271581311,var_off=(0x10300000;0x7f)) R1_w=invP808464432 R10=fp0
  9: (76) if w0 s>= 0x303030 goto pc+2
  12: (95) exit

  from 8 to 9: safe

  from 5 to 6: R0_w=invP(id=0,umin_value=808464432,umax_value=5103431727,var_off=(0x30303020;0x10000001f)) R1_w=invP808464432 R10=fp0
  6: (07) r0 += -2144337872
  7: (14) w0 -= -1607454672
  8: (25) if r0 > 0x30303030 goto pc+0
   R0_w=invP(id=0,umin_value=271581184,umax_value=271581311,var_off=(0x10300000;0x7f)) R1_w=invP808464432 R10=fp0
  9: safe

  from 8 to 9: safe
  verification time 589 usec
  stack depth 0
  processed 17 insns (limit 1000000) [...]

The underlying program was xlated as follows:

  # bpftool p d x i 9
   0: (b7) r0 = 808464432
   1: (7f) r0 >>= r0
   2: (14) w0 -= 808464432
   3: (07) r0 += 808464432
   4: (b7) r1 = 808464432
   5: (de) if w1 s<= w0 goto pc+0
   6: (07) r0 += -2144337872
   7: (14) w0 -= -1607454672
   8: (25) if r0 > 0x30303030 goto pc+0
   9: (76) if w0 s>= 0x303030 goto pc+2
  10: (05) goto pc-1
  11: (05) goto pc-1
  12: (95) exit

The verifier rewrote original instructions it recognized as dead code with
'goto pc-1', but reality differs from verifier simulation in that we're
actually able to trigger a hang due to hitting the 'goto pc-1' instructions.

Taking different examples to make the issue more obvious: in this example
we're probing bounds on a completely unknown scalar variable in r1:

  [...]
  5: R0_w=inv1 R1_w=inv(id=0) R10=fp0
  5: (18) r2 = 0x4000000000
  7: R0_w=inv1 R1_w=inv(id=0) R2_w=inv274877906944 R10=fp0
  7: (18) r3 = 0x2000000000
  9: R0_w=inv1 R1_w=inv(id=0) R2_w=inv274877906944 R3_w=inv137438953472 R10=fp0
  9: (18) r4 = 0x400
  11: R0_w=inv1 R1_w=inv(id=0) R2_w=inv274877906944 R3_w=inv137438953472 R4_w=inv1024 R10=fp0
  11: (18) r5 = 0x200
  13: R0_w=inv1 R1_w=inv(id=0) R2_w=inv274877906944 R3_w=inv137438953472 R4_w=inv1024 R5_w=inv512 R10=fp0
  13: (2d) if r1 > r2 goto pc+4
   R0_w=inv1 R1_w=inv(id=0,umax_value=274877906944,var_off=(0x0; 0x7fffffffff)) R2_w=inv274877906944 R3_w=inv137438953472 R4_w=inv1024 R5_w=inv512 R10=fp0
  14: R0_w=inv1 R1_w=inv(id=0,umax_value=274877906944,var_off=(0x0; 0x7fffffffff)) R2_w=inv274877906944 R3_w=inv137438953472 R4_w=inv1024 R5_w=inv512 R10=fp0
  14: (ad) if r1 < r3 goto pc+3
   R0_w=inv1 R1_w=inv(id=0,umin_value=137438953472,umax_value=274877906944,var_off=(0x0; 0x7fffffffff)) R2_w=inv274877906944 R3_w=inv137438953472 R4_w=inv1024 R5_w=inv512 R10=fp0
  15: R0=inv1 R1=inv(id=0,umin_value=137438953472,umax_value=274877906944,var_off=(0x0; 0x7fffffffff)) R2=inv274877906944 R3=inv137438953472 R4=inv1024 R5=inv512 R10=fp0
  15: (2e) if w1 > w4 goto pc+2
   R0=inv1 R1=inv(id=0,umin_value=137438953472,umax_value=274877906944,var_off=(0x0; 0x7f00000000)) R2=inv274877906944 R3=inv137438953472 R4=inv1024 R5=inv512 R10=fp0
  16: R0=inv1 R1=inv(id=0,umin_value=137438953472,umax_value=274877906944,var_off=(0x0; 0x7f00000000)) R2=inv274877906944 R3=inv137438953472 R4=inv1024 R5=inv512 R10=fp0
  16: (ae) if w1 < w5 goto pc+1
   R0=inv1 R1=inv(id=0,umin_value=137438953472,umax_value=274877906944,var_off=(0x0; 0x7f00000000)) R2=inv274877906944 R3=inv137438953472 R4=inv1024 R5=inv512 R10=fp0
  [...]

We're first probing lower/upper bounds via jmp64, later we do a similar
check via jmp32 and examine the resulting var_off there. After fall-through
in insn 14, we get the following bounded r1 with 0x7fffffffff unknown marked
bits in the variable section.

Thus, after knowing r1 <= 0x4000000000 and r1 >= 0x2000000000:

  max: 0b100000000000000000000000000000000000000 / 0x4000000000
  var: 0b111111111111111111111111111111111111111 / 0x7fffffffff
  min: 0b010000000000000000000000000000000000000 / 0x2000000000

Now, in insn 15 and 16, we perform a similar probe with lower/upper bounds
in jmp32.

Thus, after knowing r1 <= 0x4000000000 and r1 >= 0x2000000000 and
                    w1 <= 0x400        and w1 >= 0x200:

  max: 0b100000000000000000000000000000000000000 / 0x4000000000
  var: 0b111111100000000000000000000000000000000 / 0x7f00000000
  min: 0b010000000000000000000000000000000000000 / 0x2000000000

The lower/upper bounds haven't changed since they have high bits set in
u64 space and the jmp32 tests can only refine bounds in the low bits.

However, for the var part the expectation would have been 0x7f000007ff
or something less precise up to 0x7fffffffff. A outcome of 0x7f00000000
is not correct since it would contradict the earlier probed bounds
where we know that the result should have been in [0x200,0x400] in u32
space. Therefore, tests with such info will lead to wrong verifier
assumptions later on like falsely predicting conditional jumps to be
always taken, etc.

The issue here is that __reg_bound_offset32()'s implementation from
commit 581738a6 ("bpf: Provide better register bounds after jmp32
instructions") makes an incorrect range assumption:

  static void __reg_bound_offset32(struct bpf_reg_state *reg)
  {
        u64 mask = 0xffffFFFF;
        struct tnum range = tnum_range(reg->umin_value & mask,
                                       reg->umax_value & mask);
        struct tnum lo32 = tnum_cast(reg->var_off, 4);
        struct tnum hi32 = tnum_lshift(tnum_rshift(reg->var_off, 32), 32);

        reg->var_off = tnum_or(hi32, tnum_intersect(lo32, range));
  }

In the above walk-through example, __reg_bound_offset32() as-is chose
a range after masking with 0xffffffff of [0x0,0x0] since umin:0x2000000000
and umax:0x4000000000 and therefore the lo32 part was clamped to 0x0 as
well. However, in the umin:0x2000000000 and umax:0x4000000000 range above
we'd end up with an actual possible interval of [0x0,0xffffffff] for u32
space instead.

In case of the original reproducer, the situation looked as follows at
insn 5 for r0:

  [...]
  5: R0_w=invP(id=0,umin_value=808464432,umax_value=5103431727,var_off=(0x0; 0x1ffffffff)) R1_w=invP808464432 R10=fp0
                               0x30303030           0x13030302f
  5: (de) if w1 s<= w0 goto pc+0
   R0_w=invP(id=0,umin_value=808464432,umax_value=5103431727,var_off=(0x30303020; 0x10000001f)) R1_w=invP808464432 R10=fp0
                             0x30303030           0x13030302f
  [...]

After the fall-through, we similarly forced the var_off result into
the wrong range [0x30303030,0x3030302f] suggesting later on that fixed
bits must only be of 0x30303020 with 0x10000001f unknowns whereas such
assumption can only be made when both bounds in hi32 range match.

Originally, I was thinking to fix this by moving reg into a temp reg and
use proper coerce_reg_to_size() helper on the temp reg where we can then
based on that define the range tnum for later intersection:

  static void __reg_bound_offset32(struct bpf_reg_state *reg)
  {
        struct bpf_reg_state tmp = *reg;
        struct tnum lo32, hi32, range;

        coerce_reg_to_size(&tmp, 4);
        range = tnum_range(tmp.umin_value, tmp.umax_value);
        lo32 = tnum_cast(reg->var_off, 4);
        hi32 = tnum_lshift(tnum_rshift(reg->var_off, 32), 32);
        reg->var_off = tnum_or(hi32, tnum_intersect(lo32, range));
  }

In the case of the concrete example, this gives us a more conservative unknown
section. Thus, after knowing r1 <= 0x4000000000 and r1 >= 0x2000000000 and
                             w1 <= 0x400        and w1 >= 0x200:

  max: 0b100000000000000000000000000000000000000 / 0x4000000000
  var: 0b111111111111111111111111111111111111111 / 0x7fffffffff
  min: 0b010000000000000000000000000000000000000 / 0x2000000000

However, above new __reg_bound_offset32() has no effect on refining the
knowledge of the register contents. Meaning, if the bounds in hi32 range
mismatch we'll get the identity function given the range reg spans
[0x0,0xffffffff] and we cast var_off into lo32 only to later on binary
or it again with the hi32.

Likewise, if the bounds in hi32 range match, then we mask both bounds
with 0xffffffff, use the resulting umin/umax for the range to later
intersect the lo32 with it. However, _prior_ called __reg_bound_offset()
did already such intersection on the full reg and we therefore would only
repeat the same operation on the lo32 part twice.

Given this has no effect and the original commit had false assumptions,
this patch reverts the code entirely which is also more straight forward
for stable trees: apparently 581738a6 got auto-selected by Sasha's
ML system and misclassified as a fix, so it got sucked into v5.4 where
it should never have landed. A revert is low-risk also from a user PoV
since it requires a recent kernel and llc to opt-into -mcpu=v3 BPF CPU
to generate jmp32 instructions. A proper bounds refinement would need a
significantly more complex approach which is currently being worked, but
no stable material [0]. Hence revert is best option for stable. After the
revert, the original reported program gets rejected as follows:

  1: (7f) r0 >>= r0
  2: (14) w0 -= 808464432
  3: (07) r0 += 808464432
  4: (b7) r1 = 808464432
  5: (de) if w1 s<= w0 goto pc+0
   R0_w=invP(id=0,umin_value=808464432,umax_value=5103431727,var_off=(0x0; 0x1ffffffff)) R1_w=invP808464432 R10=fp0
  6: (07) r0 += -2144337872
  7: (14) w0 -= -1607454672
  8: (25) if r0 > 0x30303030 goto pc+0
   R0_w=invP(id=0,umax_value=808464432,var_off=(0x0; 0x3fffffff)) R1_w=invP808464432 R10=fp0
  9: (76) if w0 s>= 0x303030 goto pc+2
   R0=invP(id=0,umax_value=3158063,var_off=(0x0; 0x3fffff)) R1=invP808464432 R10=fp0
  10: (30) r0 = *(u8 *)skb[808464432]
  BPF_LD_[ABS|IND] uses reserved fields
  processed 11 insns (limit 1000000) [...]

  [0] https://lore.kernel.org/bpf/158507130343.15666.8018068546764556975.stgit@john-Precision-5820-Tower/T/

Fixes: 581738a6

 ("bpf: Provide better register bounds after jmp32 instructions")
Reported-by: Anatoly Trosinenko <anatoly.trosinenko@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200330160324.15259-2-daniel@iogearbox.net

KP Singh says:

====================
** Motivation

Google does analysis of rich runtime security data to detect and thwart
threats in real-time. Currently, this is done in custom kernel modules
but we would like to replace this with something that's upstream and
useful to others.

The current kernel infrastructure for providing telemetry (Audit, Perf
etc.) is disjoint from access enforcement (i.e. LSMs).  Augmenting the
information provided by audit requires kernel changes to audit, its
policy language and user-space components. Furthermore, building a MAC
policy based on the newly added telemetry data requires changes to
various LSMs and their respective policy languages.

This patchset allows BPF programs to be attached to LSM hooks This
facilitates a unified and dynamic (not requiring re-compilation of the
kernel) audit and MAC policy.

** Why an LSM?

Linux Security Modules target security behaviours rather than the
kernel's API. For example, it's easy to miss out a newly added system
call for executing processes (eg. execve, execveat etc.) but the LSM
framework ensures that all process executions trigger the relevant hooks
irrespective of how the process was executed.

Allowing users to implement LSM hooks at runtime also benefits the LSM
eco-system by enabling a quick feedback loop from the security community
about the kind of behaviours that the LSM Framework should be targeting.

** How does it work?

The patchset introduces a new eBPF (https://docs.cilium.io/en/v1.6/bpf/)
program type BPF_PROG_TYPE_LSM which can only be attached to LSM hooks.
Loading and attachment of BPF programs requires CAP_SYS_ADMIN.

The new LSM registers nop functions (bpf_lsm_<hook_name>) as LSM hook
callbacks. Their purpose is to provide a definite point where BPF
programs can be attached as BPF_TRAMP_MODIFY_RETURN trampoline programs
for hooks that return an int, and BPF_TRAMP_FEXIT trampoline programs
for void LSM hooks.

Audit logs can be written using a format chosen by the eBPF program to
the perf events buffer or to global eBPF variables or maps and can be
further processed in user-space.

** BTF Based Design

The current design uses BTF:

  * https://facebookmicrosites.github.io/bpf/blog/2018/11/14/btf-enhancement.html
  * https://lwn.net/Articles/803258

which allows verifiable read-only structure accesses by field names
rather than fixed offsets. This allows accessing the hook parameters
using a dynamically created context which provides a certain degree of
ABI stability:

  // Only declare the structure and fields intended to be used
  // in the program
  struct vm_area_struct {
    unsigned long vm_start;
  } __attribute__((preserve_access_index));

  // Declare the eBPF program mprotect_audit which attaches to
  // to the file_mprotect LSM hook and accepts three arguments.
  SEC("lsm/file_mprotect")
  int BPF_PROG(mprotect_audit, struct vm_area_struct *vma,
         unsigned long reqprot, unsigned long prot, int ret)
  {
    unsigned long vm_start = vma->vm_start;
    return 0;
  }

By relocating field offsets, BTF makes a large portion of kernel data
structures readily accessible across kernel versions without requiring a
large corpus of BPF helper functions and requiring recompilation with
every kernel version. The BTF type information is also used by the BPF
verifier to validate memory accesses within the BPF program and also
prevents arbitrary writes to the kernel memory.

The limitations of BTF compatibility are described in BPF Co-Re
(http://vger.kernel.org/bpfconf2019_talks/bpf-core.pdf, i.e. field
renames, #defines and changes to the signature of LSM hooks).  This
design imposes that the MAC policy (eBPF programs) be updated when the
inspected kernel structures change outside of BTF compatibility
guarantees. In practice, this is only required when a structure field
used by a current policy is removed (or renamed) or when the used LSM
hooks change. We expect the maintenance cost of these changes to be
acceptable as compared to the design presented in the RFC.

(https://lore.kernel.org/bpf/20190910115527.5235-1-kpsingh@chromium.org/).

** Usage Examples

A simple example and some documentation is included in the patchset.
In order to better illustrate the capabilities of the framework some
more advanced prototype (not-ready for review) code has also been
published separately:

* Logging execution events (including environment variables and
  arguments)
  https://github.com/sinkap/linux-krsi/blob/patch/v1/examples/samples/bpf/lsm_audit_env.c

* Detecting deletion of running executables:
  https://github.com/sinkap/linux-krsi/blob/patch/v1/examples/samples/bpf/lsm_detect_exec_unlink.c

* Detection of writes to /proc/<pid>/mem:
  https://github.com/sinkap/linux-krsi/blob/patch/v1/examples/samples/bpf/lsm_audit_env.c

We have updated Google's internal telemetry infrastructure and have
started deploying this LSM on our Linux Workstations. This gives us more
confidence in the real-world applications of such a system.

** Changelog:

- v8 -> v9:
  https://lore.kernel.org/bpf/20200327192854.31150-1-kpsingh@chromium.org/
* Fixed a selftest crash when CONFIG_LSM doesn't have "bpf".
* Added James' Ack.
* Rebase.

- v7 -> v8:
  https://lore.kernel.org/bpf/20200326142823.26277-1-kpsingh@chromium.org/
* Removed CAP_MAC_ADMIN check from bpf_lsm_verify_prog. LSMs can add it
  in their own bpf_prog hook. This can be revisited as a separate patch.
* Added Andrii and James' Ack/Review tags.
* Fixed an indentation issue and missing newlines in selftest error
  a cases.
* Updated a comment as suggested by Alexei.
* Updated the documentation to use the newer libbpf API and some other
  fixes.
* Rebase

- v6 -> v7:
  https://lore.kernel.org/bpf/20200325152629.6904-1-kpsingh@chromium.org/
* Removed __weak from the LSM attachment nops per Kees' suggestion.
  Will send a separate patch (if needed) to update the noinline
  definition in include/linux/compiler_attributes.h.
* waitpid to wait specifically for the forked child in selftests.
* Comment format fixes in security/... as suggested by Casey.
* Added Acks from Kees and Andrii and Casey's Reviewed-by: tags to
  the respective patches.
* Rebase

- v5 -> v6:
  https://lore.kernel.org/bpf/20200323164415.12943-1-kpsingh@chromium.org/
* Updated LSM_HOOK macro to define a default value and cleaned up the
  BPF LSM hook declarations.
* Added Yonghong's Acks and Kees' Reviewed-by tags.
* Simplification of the selftest code.
* Rebase and fixes suggested by Andrii and Yonghong and some other minor
  fixes noticed in internal review.

- v4 -> v5:
  https://lore.kernel.org/bpf/20200220175250.10795-1-kpsingh@chromium.org/
* Removed static keys and special casing of BPF calls from the LSM
  framework.
* Initialized the BPF callbacks (nops) as proper LSM hooks.
* Updated to using the newly introduced BPF_TRAMP_MODIFY_RETURN
  trampolines in https://lkml.org/lkml/2020/3/4/877
* Addressed Andrii's feedback and rebased.

- v3 -> v4:
* Moved away from allocating a separate security_hook_heads and adding a
  new special case for arch_prepare_bpf_trampoline to using BPF fexit
  trampolines called from the right place in the LSM hook and toggled by
  static keys based on the discussion in:
  https://lore.kernel.org/bpf/CAG48ez25mW+_oCxgCtbiGMX07g_ph79UOJa07h=o_6B6+Q-u5g@mail.gmail.com/
* Since the code does not deal with security_hook_heads anymore, it goes
  from "being a BPF LSM" to "BPF program attachment to LSM hooks".
* Added a new test case which ensures that the BPF programs' return value
  is reflected by the LSM hook.

- v2 -> v3 does not change the overall design and has some minor fixes:
* LSM_ORDER_LAST is introduced to represent the behaviour of the BPF LSM
* Fixed the inadvertent clobbering of the LSM Hook error codes
* Added GPL license requirement to the commit log
* The lsm_hook_idx is now the more conventional 0-based index
* Some changes were split into a separate patch ("Load btf_vmlinux only
  once per object")
  https://lore.kernel.org/bpf/20200117212825.11755-1-kpsingh@chromium.org/
* Addressed Andrii's feedback on the BTF implementation
* Documentation update for using generated vmlinux.h to simplify
  programs
* Rebase

- Changes since v1:
  https://lore.kernel.org/bpf/20191220154208.15895-1-kpsingh@chromium.org
* Eliminate the requirement to maintain LSM hooks separately in
  security/bpf/hooks.h Use BPF trampolines to dynamically allocate
  security hooks
* Drop the use of securityfs as bpftool provides the required
  introspection capabilities.  Update the tests to use the bpf_skeleton
  and global variables
* Use O_CLOEXEC anonymous fds to represent BPF attachment in line with
  the other BPF programs with the possibility to use bpf program pinning
  in the future to provide "permanent attachment".
* Drop the logic based on prog names for handling re-attachment.
* Drop bpf_lsm_event_output from this series and send it as a separate
  patch.
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Document how eBPF programs (BPF_PROG_TYPE_LSM) can be loaded and
attached (BPF_LSM_MAC) to the LSM hooks.

Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Florent Revest <revest@google.com>
Reviewed-by: Thomas Garnier <thgarnie@google.com>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Link: https://lore.kernel.org/bpf/20200329004356.27286-9-kpsingh@chromium.org

* Load/attach a BPF program that hooks to file_mprotect (int)
  and bprm_committed_creds (void).
* Perform an action that triggers the hook.
* Verify if the audit event was received using the shared global
  variables for the process executed.
* Verify if the mprotect returns a -EPERM.

Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Florent Revest <revest@google.com>
Reviewed-by: Thomas Garnier <thgarnie@google.com>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200329004356.27286-8-kpsingh@chromium.org

Since BPF_PROG_TYPE_LSM uses the same attaching mechanism as
BPF_PROG_TYPE_TRACING, the common logic is refactored into a static
function bpf_program__attach_btf_id.

A new API call bpf_program__attach_lsm is still added to avoid userspace
conflicts if this ever changes in the future.

Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Florent Revest <revest@google.com>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200329004356.27286-7-kpsingh@chromium.org

* The hooks are initialized using the definitions in
  include/linux/lsm_hook_defs.h.
* The LSM can be enabled / disabled with CONFIG_BPF_LSM.

Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Florent Revest <revest@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: James Morris <jamorris@linux.microsoft.com>
Link: https://lore.kernel.org/bpf/20200329004356.27286-6-kpsingh@chromium.org

JITed BPF programs are dynamically attached to the LSM hooks
using BPF trampolines. The trampoline prologue generates code to handle
conversion of the signature of the hook to the appropriate BPF context.

The allocated trampoline programs are attached to the nop functions
initialized as LSM hooks.

BPF_PROG_TYPE_LSM programs must have a GPL compatible license and
and need CAP_SYS_ADMIN (required for loading eBPF programs).

Upon attachment:

* A BPF fexit trampoline is used for LSM hooks with a void return type.
* A BPF fmod_ret trampoline is used for LSM hooks which return an
  int. The attached programs can override the return value of the
  bpf LSM hook to indicate a MAC Policy decision.

Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Florent Revest <revest@google.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: James Morris <jamorris@linux.microsoft.com>
Link: https://lore.kernel.org/bpf/20200329004356.27286-5-kpsingh@chromium.org

When CONFIG_BPF_LSM is enabled, nop functions, bpf_lsm_<hook_name>, are
generated for each LSM hook. These functions are initialized as LSM
hooks in a subsequent patch.

Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Florent Revest <revest@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: James Morris <jamorris@linux.microsoft.com>
Link: https://lore.kernel.org/bpf/20200329004356.27286-4-kpsingh@chromium.org

The information about the different types of LSM hooks is scattered
in two locations i.e. union security_list_options and
struct security_hook_heads. Rather than duplicating this information
even further for BPF_PROG_TYPE_LSM, define all the hooks with the
LSM_HOOK macro in lsm_hook_defs.h which is then used to generate all
the data structures required by the LSM framework.

The LSM hooks are defined as:

  LSM_HOOK(<return_type>, <default_value>, <hook_name>, args...)

with <default_value> acccessible in security.c as:

  LSM_RET_DEFAULT(<hook_name>)

Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Florent Revest <revest@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: James Morris <jamorris@linux.microsoft.com>
Link: https://lore.kernel.org/bpf/20200329004356.27286-3-kpsingh@chromium.org

Introduce types and configs for bpf programs that can be attached to
LSM hooks. The programs can be enabled by the config option
CONFIG_BPF_LSM.

Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Florent Revest <revest@google.com>
Reviewed-by: Thomas Garnier <thgarnie@google.com>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: James Morris <jamorris@linux.microsoft.com>
Link: https://lore.kernel.org/bpf/20200329004356.27286-2-kpsingh@chromium.org

This adds a test to exercise the new bpf_map__set_initial_value() function.
The test simply overrides the global data section with all zeroes, and
checks that the new value makes it into the kernel map on load.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200329132253.232541-2-toke@redhat.com

For internal maps (most notably the maps backing global variables), libbpf
uses an internal mmaped area to store the data after opening the object.
This data is subsequently copied into the kernel map when the object is
loaded.

This adds a function to set a new value for that data, which can be used to
before it is loaded into the kernel. This is especially relevant for RODATA
maps, since those are frozen on load.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200329132253.232541-1-toke@redhat.com

Fix a redefinition of 'net_gen_cookie' error that was overlooked
when net ns is not configured.

Fixes: f318903c

 ("bpf: Add netns cookie and enable it for bpf cgroup hooks")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Toke Høiland-Jørgensen says:

====================
This series adds support for atomically replacing the XDP program loaded on an
interface. This is achieved by means of a new netlink attribute that can specify
the expected previous program to replace on the interface. If set, the kernel
will compare this "expected fd" attribute with the program currently loaded on
the interface, and reject the operation if it does not match.

With this primitive, userspace applications can avoid stepping on each other's
toes when simultaneously updating the loaded XDP program.

Changelog:

v4:
- Switch back to passing FD instead of ID (Andrii)
- Rename flag to XDP_FLAGS_REPLACE (for consistency with other similar uses)

v3:
- Pass existing ID instead of FD (Jakub)
- Use opts struct for new libbpf function (Andrii)

v2:
- Fix checkpatch nits and add .strict_start_type to netlink policy (Jakub)
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

This adds tests for the various replacement operations using
IFLA_XDP_EXPECTED_FD.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/158515700967.92963.15098921624731968356.stgit@toke.dk

This adds a new function to set the XDP fd while specifying the FD of the
program to replace, using the newly added IFLA_XDP_EXPECTED_FD netlink
parameter. The new function uses the opts struct mechanism to be extendable
in the future.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/158515700857.92963.7052131201257841700.stgit@toke.dk

This adds the IFLA_XDP_EXPECTED_FD netlink attribute definition and the
XDP_FLAGS_REPLACE flag to if_link.h in tools/include.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/158515700747.92963.8615391897417388586.stgit@toke.dk

While it is currently possible for userspace to specify that an existing
XDP program should not be replaced when attaching to an interface, there is
no mechanism to safely replace a specific XDP program with another.

This patch adds a new netlink attribute, IFLA_XDP_EXPECTED_FD, which can be
set along with IFLA_XDP_FD. If set, the kernel will check that the program
currently loaded on the interface matches the expected one, and fail the
operation if it does not. This corresponds to a 'cmpxchg' memory operation.
Setting the new attribute with a negative value means that no program is
expected to be attached, which corresponds to setting the UPDATE_IF_NOEXIST
flag.

A new companion flag, XDP_FLAGS_REPLACE, is also added to explicitly
request checking of the EXPECTED_FD attribute. This is needed for userspace
to discover whether the kernel supports the new attribute.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/bpf/158515700640.92963.3551295145441017022.stgit@toke.dk

Fix build warnings when building net/bpf/test_run.o with W=1 due
to missing prototype for bpf_fentry_test{1..6}.

Instead of declaring prototypes, turn off warnings with
__diag_{push,ignore,pop} as pointed out by Alexei.

Signed-off-by: Jean-Philippe Menil <jpmenil@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200327204713.28050-1-jpmenil@gmail.com

Fix a sharp edge in xsk_umem__create and xsk_socket__create.  Almost all of
the members of the ring buffer structs are initialized, but the "cached_xxx"
variables are not all initialized.  The caller is required to zero them.
This is needlessly dangerous.  The results if you don't do it can be very bad.
For example, they can cause xsk_prod_nb_free and xsk_cons_nb_avail to return
values greater than the size of the queue.  xsk_ring_cons__peek can return an
index that does not refer to an item that has been queued.

I have confirmed that without this change, my program misbehaves unless I
memset the ring buffers to zero before calling the function.  Afterwards,
my program works without (or with) the memset.

Signed-off-by: Fletcher Dunn <fletcherd@valvesoftware.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
Link: https://lore.kernel.org/bpf/85f12913cde94b19bfcb598344701c38@valvesoftware.com

Daniel Borkmann says:

====================
This adds various straight-forward helper improvements and additions to BPF
cgroup based connect(), sendmsg(), recvmsg() and bind-related hooks which
would allow to implement more fine-grained policies and improve current load
balancer limitations we're seeing. For details please see individual patches.
I've tested them on Kubernetes & Cilium and also added selftests for the small
verifier extension. Thanks!
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Add various tests to make sure the verifier keeps catching them:

  # ./test_verifier
  [...]
  #230/p pass ctx or null check, 1: ctx OK
  #231/p pass ctx or null check, 2: null OK
  #232/p pass ctx or null check, 3: 1 OK
  #233/p pass ctx or null check, 4: ctx - const OK
  #234/p pass ctx or null check, 5: null (connect) OK
  #235/p pass ctx or null check, 6: null (bind) OK
  #236/p pass ctx or null check, 7: ctx (bind) OK
  #237/p pass ctx or null check, 8: null (bind) OK
  [...]
  Summary: 1595 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/c74758d07b1b678036465ef7f068a49e9efd3548.1585323121.git.daniel@iogearbox.net

We already have the bpf_get_current_uid_gid() helper enabled, and
given we now have perf event RB output available for connect(),
sendmsg(), recvmsg() and bind-related hooks, add a trivial change
to enable bpf_get_current_pid_tgid() and bpf_get_current_comm()
as well.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/18744744ed93c06343be8b41edcfd858706f39d7.1585323121.git.daniel@iogearbox.net

Enable the bpf_get_current_cgroup_id() helper for connect(), sendmsg(),
recvmsg() and bind-related hooks in order to retrieve the cgroup v2
context which can then be used as part of the key for BPF map lookups,
for example. Given these hooks operate in process context 'current' is
always valid and pointing to the app that is performing mentioned
syscalls if it's subject to a v2 cgroup. Also with same motivation of
commit 77236281

 ("bpf: Introduce bpf_skb_ancestor_cgroup_id helper")
enable retrieval of ancestor from current so the cgroup id can be used
for policy lookups which can then forbid connect() / bind(), for example.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/d2a7ef42530ad299e3cbb245e6c12374b72145ef.1585323121.git.daniel@iogearbox.net

Today, Kubernetes is still operating on cgroups v1, however, it is
possible to retrieve the task's classid based on 'current' out of
connect(), sendmsg(), recvmsg() and bind-related hooks for orchestrators
which attach to the root cgroup v2 hook in a mixed env like in case
of Cilium, for example, in order to then correlate certain pod traffic
and use it as part of the key for BPF map lookups.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/555e1c69db7376c0947007b4951c260e1074efc3.1585323121.git.daniel@iogearbox.net

In Cilium we're mainly using BPF cgroup hooks today in order to implement
kube-proxy free Kubernetes service translation for ClusterIP, NodePort (*),
ExternalIP, and LoadBalancer as well as HostPort mapping [0] for all traffic
between Cilium managed nodes. While this works in its current shape and avoids
packet-level NAT for inter Cilium managed node traffic, there is one major
limitation we're facing today, that is, lack of netns awareness.

In Kubernetes, the concept of Pods (which hold one or multiple containers)
has been built around network namespaces, so while we can use the global scope
of attaching to root BPF cgroup hooks also to our advantage (e.g. for exposing
NodePort ports on loopback addresses), we also have the need to differentiate
between initial network namespaces and non-initial one. For example, ExternalIP
services mandate that non-local service IPs are not to be translated from the
host (initial) network namespace as one example. Right now, we have an ugly
work-around in place where non-local service IPs for ExternalIP services are
not xlated from connect() and friends BPF hooks but instead via less efficient
packet-level NAT on the veth tc ingress hook for Pod traffic.

On top of determining whether we're in initial or non-initial network namespace
we also have a need for a socket-cookie like mechanism for network namespaces
scope. Socket cookies have the nice property that they can be combined as part
of the key structure e.g. for BPF LRU maps without having to worry that the
cookie could be recycled. We are planning to use this for our sessionAffinity
implementation for services. Therefore, add a new bpf_get_netns_cookie() helper
which would resolve both use cases at once: bpf_get_netns_cookie(NULL) would
provide the cookie for the initial network namespace while passing the context
instead of NULL would provide the cookie from the application's network namespace.
We're using a hole, so no size increase; the assignment happens only once.
Therefore this allows for a comparison on initial namespace as well as regular
cookie usage as we have today with socket cookies. We could later on enable
this helper for other program types as well as we would see need.

  (*) Both externalTrafficPolicy={Local|Cluster} types
  [0] https://github.com/cilium/cilium/blob/master/bpf/bpf_sock.c

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/c47d2346982693a9cf9da0e12690453aded4c788.1585323121.git.daniel@iogearbox.net

Currently, connect(), sendmsg(), recvmsg() and bind-related hooks
are all lacking perf event rb output in order to push notifications
or monitoring events up to user space. Back in commit a5a3a828


("bpf: add perf event notificaton support for sock_ops"), I've worked
with Sowmini to enable them for sock_ops where the context part is
not used (as opposed to skbs for example where the packet data can
be appended). Make the bpf_sockopt_event_output() helper generic and
enable it for mentioned hooks.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/69c39daf87e076b31e52473c902e9bfd37559124.1585323121.git.daniel@iogearbox.net