Commit f8d3da4e authored by Joanne Koong's avatar Joanne Koong Committed by Daniel Borkmann
Browse files

bpf: Add flags arg to bpf_dynptr_read and bpf_dynptr_write APIs 



Commit 13bbbfbe ("bpf: Add bpf_dynptr_read and bpf_dynptr_write")
added the bpf_dynptr_write() and bpf_dynptr_read() APIs.

However, it will be needed for some dynptr types to pass in flags as
well (e.g. when writing to a skb, the user may like to invalidate the
hash or recompute the checksum).

This patch adds a "u64 flags" arg to the bpf_dynptr_read() and
bpf_dynptr_write() APIs before their UAPI signature freezes where
we then cannot change them anymore with a 5.19.x released kernel.

Fixes: 13bbbfbe ("bpf: Add bpf_dynptr_read and bpf_dynptr_write")
Signed-off-by: default avatarJoanne Koong <joannelkoong@gmail.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20220706232547.4016651-1-joannelkoong@gmail.com
parent 0326195f

include/uapi/linux/bpf.h

+7 −4
Original line number Diff line number Diff line
@@ -5222,22 +5222,25 @@ union bpf_attr { 
 *	Return

 *		Nothing. Always succeeds.

 *

 * long bpf_dynptr_read(void *dst, u32 len, struct bpf_dynptr *src, u32 offset)

 * long bpf_dynptr_read(void *dst, u32 len, struct bpf_dynptr *src, u32 offset, u64 flags)

 *	Description

 *		Read *len* bytes from *src* into *dst*, starting from *offset*

 *		into *src*.

 *		*flags* is currently unused.

 *	Return

 *		0 on success, -E2BIG if *offset* + *len* exceeds the length

 *		of *src*'s data, -EINVAL if *src* is an invalid dynptr.

 *		of *src*'s data, -EINVAL if *src* is an invalid dynptr or if

 *		*flags* is not 0.

 *

 * long bpf_dynptr_write(struct bpf_dynptr *dst, u32 offset, void *src, u32 len)

 * long bpf_dynptr_write(struct bpf_dynptr *dst, u32 offset, void *src, u32 len, u64 flags)

 *	Description

 *		Write *len* bytes from *src* into *dst*, starting from *offset*

 *		into *dst*.

 *		*flags* is currently unused.

 *	Return

 *		0 on success, -E2BIG if *offset* + *len* exceeds the length

 *		of *dst*'s data, -EINVAL if *dst* is an invalid dynptr or if *dst*

 *		is a read-only dynptr.

 *		is a read-only dynptr or if *flags* is not 0.

 *

 * void *bpf_dynptr_data(struct bpf_dynptr *ptr, u32 offset, u32 len)

 *	Description

kernel/bpf/helpers.c

+8 −4
Original line number Diff line number Diff line
@@ -1497,11 +1497,12 @@ const struct bpf_func_proto bpf_dynptr_from_mem_proto = { 
	.arg4_type	= ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_LOCAL | MEM_UNINIT,

};



BPF_CALL_4(bpf_dynptr_read, void *, dst, u32, len, struct bpf_dynptr_kern *, src, u32, offset)

BPF_CALL_5(bpf_dynptr_read, void *, dst, u32, len, struct bpf_dynptr_kern *, src,

	   u32, offset, u64, flags)

{

	int err;



	if (!src->data)

	if (!src->data || flags)

		return -EINVAL;



	err = bpf_dynptr_check_off_len(src, offset, len);
@@ -1521,13 +1522,15 @@ const struct bpf_func_proto bpf_dynptr_read_proto = { 
	.arg2_type	= ARG_CONST_SIZE_OR_ZERO,

	.arg3_type	= ARG_PTR_TO_DYNPTR,

	.arg4_type	= ARG_ANYTHING,

	.arg5_type	= ARG_ANYTHING,

};



BPF_CALL_4(bpf_dynptr_write, struct bpf_dynptr_kern *, dst, u32, offset, void *, src, u32, len)

BPF_CALL_5(bpf_dynptr_write, struct bpf_dynptr_kern *, dst, u32, offset, void *, src,

	   u32, len, u64, flags)

{

	int err;



	if (!dst->data || bpf_dynptr_is_rdonly(dst))

	if (!dst->data || flags || bpf_dynptr_is_rdonly(dst))

		return -EINVAL;



	err = bpf_dynptr_check_off_len(dst, offset, len);
@@ -1547,6 +1550,7 @@ const struct bpf_func_proto bpf_dynptr_write_proto = { 
	.arg2_type	= ARG_ANYTHING,

	.arg3_type	= ARG_PTR_TO_MEM | MEM_RDONLY,

	.arg4_type	= ARG_CONST_SIZE_OR_ZERO,

	.arg5_type	= ARG_ANYTHING,

};



BPF_CALL_3(bpf_dynptr_data, struct bpf_dynptr_kern *, ptr, u32, offset, u32, len)

tools/include/uapi/linux/bpf.h

+7 −4
Original line number Diff line number Diff line
@@ -5222,22 +5222,25 @@ union bpf_attr { 
 *	Return

 *		Nothing. Always succeeds.

 *

 * long bpf_dynptr_read(void *dst, u32 len, struct bpf_dynptr *src, u32 offset)

 * long bpf_dynptr_read(void *dst, u32 len, struct bpf_dynptr *src, u32 offset, u64 flags)

 *	Description

 *		Read *len* bytes from *src* into *dst*, starting from *offset*

 *		into *src*.

 *		*flags* is currently unused.

 *	Return

 *		0 on success, -E2BIG if *offset* + *len* exceeds the length

 *		of *src*'s data, -EINVAL if *src* is an invalid dynptr.

 *		of *src*'s data, -EINVAL if *src* is an invalid dynptr or if

 *		*flags* is not 0.

 *

 * long bpf_dynptr_write(struct bpf_dynptr *dst, u32 offset, void *src, u32 len)

 * long bpf_dynptr_write(struct bpf_dynptr *dst, u32 offset, void *src, u32 len, u64 flags)

 *	Description

 *		Write *len* bytes from *src* into *dst*, starting from *offset*

 *		into *dst*.

 *		*flags* is currently unused.

 *	Return

 *		0 on success, -E2BIG if *offset* + *len* exceeds the length

 *		of *dst*'s data, -EINVAL if *dst* is an invalid dynptr or if *dst*

 *		is a read-only dynptr.

 *		is a read-only dynptr or if *flags* is not 0.

 *

 * void *bpf_dynptr_data(struct bpf_dynptr *ptr, u32 offset, u32 len)

 *	Description

tools/testing/selftests/bpf/progs/dynptr_fail.c

+5 −5
Original line number Diff line number Diff line
@@ -140,12 +140,12 @@ int use_after_invalid(void *ctx) 


	bpf_ringbuf_reserve_dynptr(&ringbuf, sizeof(read_data), 0, &ptr);



	bpf_dynptr_read(read_data, sizeof(read_data), &ptr, 0);

	bpf_dynptr_read(read_data, sizeof(read_data), &ptr, 0, 0);



	bpf_ringbuf_submit_dynptr(&ptr, 0);



	/* this should fail */

	bpf_dynptr_read(read_data, sizeof(read_data), &ptr, 0);

	bpf_dynptr_read(read_data, sizeof(read_data), &ptr, 0, 0);



	return 0;

}
@@ -338,7 +338,7 @@ int invalid_helper2(void *ctx) 
	get_map_val_dynptr(&ptr);



	/* this should fail */

	bpf_dynptr_read(read_data, sizeof(read_data), (void *)&ptr + 8, 0);

	bpf_dynptr_read(read_data, sizeof(read_data), (void *)&ptr + 8, 0, 0);



	return 0;

}
@@ -377,7 +377,7 @@ int invalid_write2(void *ctx) 
	memcpy((void *)&ptr + 8, &x, sizeof(x));



	/* this should fail */

	bpf_dynptr_read(read_data, sizeof(read_data), &ptr, 0);

	bpf_dynptr_read(read_data, sizeof(read_data), &ptr, 0, 0);



	bpf_ringbuf_submit_dynptr(&ptr, 0);
@@ -473,7 +473,7 @@ int invalid_read2(void *ctx) 
	get_map_val_dynptr(&ptr);



	/* this should fail */

	bpf_dynptr_read(read_data, sizeof(read_data), (void *)&ptr + 1, 0);

	bpf_dynptr_read(read_data, sizeof(read_data), (void *)&ptr + 1, 0, 0);



	return 0;

}

tools/testing/selftests/bpf/progs/dynptr_success.c

+2 −2
Original line number Diff line number Diff line
@@ -43,10 +43,10 @@ int test_read_write(void *ctx) 
	bpf_ringbuf_reserve_dynptr(&ringbuf, sizeof(write_data), 0, &ptr);



	/* Write data into the dynptr */

	err = err ?: bpf_dynptr_write(&ptr, 0, write_data, sizeof(write_data));

	err = bpf_dynptr_write(&ptr, 0, write_data, sizeof(write_data), 0);



	/* Read the data that was written into the dynptr */

	err = err ?: bpf_dynptr_read(read_data, sizeof(read_data), &ptr, 0);

	err = err ?: bpf_dynptr_read(read_data, sizeof(read_data), &ptr, 0, 0);



	/* Ensure the data we read matches the data we wrote */

	for (i = 0; i < sizeof(read_data); i++) {