From: Mykyta Yatsenko <yatsenko@meta.com> mainline inclusion from mainline-v7.1-rc1 commit 4d0a375887ab4d49e4da1ff10f9606cab8f7c3ad category: bugfix bugzilla: https://atomgit.com/openeuler/kernel/issues/9180 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- 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> Conflicts: kernel/bpf/verifier.c [ctx conflicts] Signed-off-by: Pu Lehui <pulehui@huawei.com> --- kernel/bpf/verifier.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 0f61022fd885..b24bcb6af69c 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5376,6 +5376,9 @@ 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; @@ -5386,7 +5389,7 @@ static int map_kptr_match_type(struct bpf_verifier_env *env, perm_flags = PTR_MAYBE_NULL | MEM_ALLOC; } - 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 */ -- 2.34.1