Commit cb578c1c authored by Eduard Zingerman's avatar Eduard Zingerman Committed by Alexei Starovoitov
Browse files

selftests/bpf: test cases for regsafe() bug skipping check_id() 



Under certain conditions it was possible for verifier.c:regsafe() to
skip check_id() call. This commit adds negative test cases previously
errorneously accepted as safe.

Signed-off-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20221209135733.28851-3-eddyz87@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 7c884339

tools/testing/selftests/bpf/verifier/direct_packet_access.c

+54 −0
Original line number Diff line number Diff line
@@ -654,3 +654,57 @@ 
	.result = ACCEPT,

	.prog_type = BPF_PROG_TYPE_SCHED_CLS,

},

{

	"direct packet access: test30 (check_id() in regsafe(), bad access)",

	.insns = {

	/* r9 = ctx */

	BPF_MOV64_REG(BPF_REG_9, BPF_REG_1),

	/* r7 = ktime_get_ns() */

	BPF_EMIT_CALL(BPF_FUNC_ktime_get_ns),

	BPF_MOV64_REG(BPF_REG_7, BPF_REG_0),

	/* r6 = ktime_get_ns() */

	BPF_EMIT_CALL(BPF_FUNC_ktime_get_ns),

	BPF_MOV64_REG(BPF_REG_6, BPF_REG_0),

	/* r2 = ctx->data

	 * r3 = ctx->data

	 * r4 = ctx->data_end

	 */

	BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_9, offsetof(struct __sk_buff, data)),

	BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_9, offsetof(struct __sk_buff, data)),

	BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_9, offsetof(struct __sk_buff, data_end)),

	/* if r6 > 100 goto exit

	 * if r7 > 100 goto exit

	 */

	BPF_JMP_IMM(BPF_JGT, BPF_REG_6, 100, 9),

	BPF_JMP_IMM(BPF_JGT, BPF_REG_7, 100, 8),

	/* r2 += r6              ; this forces assignment of ID to r2

	 * r2 += 1               ; get some fixed off for r2

	 * r3 += r7              ; this forces assignment of ID to r3

	 * r3 += 1               ; get some fixed off for r3

	 */

	BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_6),

	BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, 1),

	BPF_ALU64_REG(BPF_ADD, BPF_REG_3, BPF_REG_7),

	BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, 1),

	/* if r6 > r7 goto +1    ; no new information about the state is derived from

	 *                       ; this check, thus produced verifier states differ

	 *                       ; only in 'insn_idx'

	 * r2 = r3               ; optionally share ID between r2 and r3

	 */

	BPF_JMP_REG(BPF_JNE, BPF_REG_6, BPF_REG_7, 1),

	BPF_MOV64_REG(BPF_REG_2, BPF_REG_3),

	/* if r3 > ctx->data_end goto exit */

	BPF_JMP_REG(BPF_JGT, BPF_REG_3, BPF_REG_4, 1),

	/* r5 = *(u8 *) (r2 - 1) ; access packet memory using r2,

	 *                       ; this is not always safe

	 */

	BPF_LDX_MEM(BPF_B, BPF_REG_5, BPF_REG_2, -1),

	/* exit(0) */

	BPF_MOV64_IMM(BPF_REG_0, 0),

	BPF_EXIT_INSN(),

	},

	.flags = BPF_F_TEST_STATE_FREQ,

	.result = REJECT,

	.errstr = "invalid access to packet, off=0 size=1, R2",

	.prog_type = BPF_PROG_TYPE_SCHED_CLS,

},

tools/testing/selftests/bpf/verifier/value_or_null.c

+49 −0
Original line number Diff line number Diff line
@@ -169,3 +169,52 @@ 
	.prog_type = BPF_PROG_TYPE_SCHED_CLS,

	.result = ACCEPT,

},

{

	"MAP_VALUE_OR_NULL check_ids() in regsafe()",

	.insns = {

	BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),

	/* r9 = map_lookup_elem(...) */

	BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),

	BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),

	BPF_LD_MAP_FD(BPF_REG_1,

		      0),

	BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),

	BPF_MOV64_REG(BPF_REG_9, BPF_REG_0),

	/* r8 = map_lookup_elem(...) */

	BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),

	BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),

	BPF_LD_MAP_FD(BPF_REG_1,

		      0),

	BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),

	BPF_MOV64_REG(BPF_REG_8, BPF_REG_0),

	/* r7 = ktime_get_ns() */

	BPF_EMIT_CALL(BPF_FUNC_ktime_get_ns),

	BPF_MOV64_REG(BPF_REG_7, BPF_REG_0),

	/* r6 = ktime_get_ns() */

	BPF_EMIT_CALL(BPF_FUNC_ktime_get_ns),

	BPF_MOV64_REG(BPF_REG_6, BPF_REG_0),

	/* if r6 > r7 goto +1    ; no new information about the state is derived from

	 *                       ; this check, thus produced verifier states differ

	 *                       ; only in 'insn_idx'

	 * r9 = r8               ; optionally share ID between r9 and r8

	 */

	BPF_JMP_REG(BPF_JGT, BPF_REG_6, BPF_REG_7, 1),

	BPF_MOV64_REG(BPF_REG_9, BPF_REG_8),

	/* if r9 == 0 goto <exit> */

	BPF_JMP_IMM(BPF_JEQ, BPF_REG_9, 0, 1),

	/* read map value via r8, this is not always

	 * safe because r8 might be not equal to r9.

	 */

	BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_8, 0),

	/* exit 0 */

	BPF_MOV64_IMM(BPF_REG_0, 0),

	BPF_EXIT_INSN(),

	},

	.flags = BPF_F_TEST_STATE_FREQ,

	.fixup_map_hash_8b = { 3, 9 },

	.result = REJECT,

	.errstr = "R8 invalid mem access 'map_value_or_null'",

	.result_unpriv = REJECT,

	.errstr_unpriv = "",

	.prog_type = BPF_PROG_TYPE_CGROUP_SKB,

},