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

Browse source 
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: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20221209135733.28851-3-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Eduard Zingerman 2022-12-09 15:57:28 +02:00 committed by Alexei Starovoitov
parent 7c884339bb
commit cb578c1c9c
2 changed files with 103 additions and 0 deletions
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54
tools/testing/selftests/bpf/verifier/direct_packet_access.c
View file

@ -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,
},

49
tools/testing/selftests/bpf/verifier/value_or_null.c
View file

@ -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,
},