diff options
| author | Eduard Zingerman <eddyz87@gmail.com> | 2026-09-04 17:05:52 -0700 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2026-09-04 18:17:29 -0700 |
| commit | 1a3a10b030c96ea88868ccc060a16827c01eaa5a (patch) | |
| tree | d374663baaac75b1b59540f22cefc6632d92d114 | |
| parent | 519f858317afc52e986817ad63fd68172dd38b6c (diff) | |
| download | linux-next-1a3a10b030c96ea88868ccc060a16827c01eaa5a.tar.gz linux-next-1a3a10b030c96ea88868ccc060a16827c01eaa5a.zip | |
bpf: mark a NULL call argument precise
check_func_arg() allows bpf_register_is_null() for nullable arguments
w/o marking the underlying scalar register precise. Hence a checkpoint
created on such a path would prune against arbitrary scalar value.
check_helper_call() enforces second parameter of the
bpf_get_local_storage() to be zero, w/o marking the underlying scalar
register precise. Hence a checkpoint created on such a path would
prune against arbitrary scalar value.
Grouping these two into one patch, as they share the same fixes tag.
Fixes: b5dc0163d8fd ("bpf: precise scalar_value tracking")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-1-0f5a360ff15d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
| -rw-r--r-- | kernel/bpf/verifier.c | 9 | ||||
| -rw-r--r-- | tools/testing/selftests/bpf/progs/verifier_subprog_precision.c | 12 |
2 files changed, 14 insertions, 7 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index c8699a8831df..b107f551a62d 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -8759,11 +8759,15 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, return err; } - if (bpf_register_is_null(reg) && type_may_be_null(arg_type)) + if (bpf_register_is_null(reg) && type_may_be_null(arg_type)) { /* A NULL register has a SCALAR_VALUE type, so skip * type checking. */ + err = mark_chain_precision(env, regno); + if (err) + return err; goto skip_type_check; + } /* arg_btf_id and arg_size are in a union. */ if (base_type(arg_type) == ARG_PTR_TO_BTF_ID || @@ -10923,6 +10927,9 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn verbose(env, "get_local_storage() doesn't support non-zero flags\n"); return -EINVAL; } + err = mark_chain_precision(env, BPF_REG_2); + if (err) + return err; break; case BPF_FUNC_for_each_map_elem: err = push_callback_call(env, insn, insn_idx, meta.subprogno, diff --git a/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c b/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c index e174a905c562..dc0c7034c04f 100644 --- a/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c +++ b/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c @@ -287,9 +287,9 @@ __msg("17: (b7) r0 = 0") __msg("18: (95) exit") __msg("returning from callee:") __msg("to caller at 9:") -__msg("frame 0: propagating r1,r4") +__msg("frame 0: propagating r1,r3,r4") __msg("mark_precise: frame0: last_idx 9 first_idx 9 subseq_idx -1") -__msg("mark_precise: frame0: regs=r1,r4 stack= before 18: (95) exit") +__msg("mark_precise: frame0: regs=r1,r3,r4 stack= before 18: (95) exit") __msg("from 18 to 9: safe") __naked int callback_result_precise(void) { @@ -419,9 +419,9 @@ __msg("to caller at 9:") /* r1, r4 are always precise for bpf_loop(), * r6 was marked before backtracking to callback body. */ -__msg("frame 0: propagating r1,r4,r6") +__msg("frame 0: propagating r1,r3,r4,r6") __msg("mark_precise: frame0: last_idx 9 first_idx 9 subseq_idx -1") -__msg("mark_precise: frame0: regs=r1,r4,r6 stack= before 16: (95) exit") +__msg("mark_precise: frame0: regs=r1,r3,r4,r6 stack= before 16: (95) exit") __msg("mark_precise: frame1: regs= stack= before 15: (b7) r0 = 0") __msg("mark_precise: frame1: regs= stack= before 9: (85) call bpf_loop") __msg("mark_precise: frame0: parent state regs= stack=:") @@ -575,9 +575,9 @@ __msg("to caller at 10:") /* r1, r4 are always precise for bpf_loop(), * fp-8 was marked before backtracking to callback body. */ -__msg("frame 0: propagating r1,r4,fp-8") +__msg("frame 0: propagating r1,r3,r4,fp-8") __msg("mark_precise: frame0: last_idx 10 first_idx 10 subseq_idx -1") -__msg("mark_precise: frame0: regs=r1,r4 stack=-8 before 18: (95) exit") +__msg("mark_precise: frame0: regs=r1,r3,r4 stack=-8 before 18: (95) exit") __msg("mark_precise: frame1: regs= stack= before 17: (b7) r0 = 0") __msg("mark_precise: frame1: regs= stack= before 10: (85) call bpf_loop#181") __msg("mark_precise: frame0: parent state regs= stack=:") |