diff options
| author | Mykyta Yatsenko <yatsenko@meta.com> | 2026-04-16 11:08:07 -0700 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2026-04-16 15:20:26 -0700 |
| commit | 4d0a375887ab4d49e4da1ff10f9606cab8f7c3ad (patch) | |
| tree | cba7dc3dcf30499d60dd71a758cef007de7af618 /kernel | |
| parent | e5f635edd393aeaa7cad9e42831d397e6e2e1eed (diff) | |
bpf: Fix NULL deref in map_kptr_match_type for scalar regs
Commit ab6c637ad027 ("bpf: Fix a bpf_kptr_xchg() issue with local
kptr") refactored map_kptr_match_type() to branch on btf_is_kernel()
before checking base_type(). A scalar register stored into a kptr
slot has no btf, so the btf_is_kernel(reg->btf) call dereferences
NULL.
Move the base_type() != PTR_TO_BTF_ID guard before any reg->btf
access.
Fixes: ab6c637ad027 ("bpf: Fix a bpf_kptr_xchg() issue with local kptr")
Reported-by: Hiker Cl <clhiker365@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221372
Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Acked-by: Paul Chaignon <paul.chaignon@gmail.com>
Link: https://lore.kernel.org/r/20260416-kptr_crash-v1-1-5589356584b4@meta.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/verifier.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 1e36b9e91277..69d75515ed3f 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4549,6 +4549,9 @@ static int map_kptr_match_type(struct bpf_verifier_env *env, int perm_flags; const char *reg_name = ""; + if (base_type(reg->type) != PTR_TO_BTF_ID) + goto bad_type; + if (btf_is_kernel(reg->btf)) { perm_flags = PTR_MAYBE_NULL | PTR_TRUSTED | MEM_RCU; @@ -4561,7 +4564,7 @@ static int map_kptr_match_type(struct bpf_verifier_env *env, perm_flags |= MEM_PERCPU; } - if (base_type(reg->type) != PTR_TO_BTF_ID || (type_flag(reg->type) & ~perm_flags)) + if (type_flag(reg->type) & ~perm_flags) goto bad_type; /* We need to verify reg->type and reg->btf, before accessing reg->btf */ |