From: Martin KaFai Lau Date: Wed, 30 Mar 2022 01:14:56 +0000 (-0700) Subject: bpf: Resolve to prog->aux->dst_prog->type only for BPF_PROG_TYPE_EXT X-Git-Tag: microblaze-v5.20~489^2~1^2~3 X-Git-Url: http://git.monstr.eu/?a=commitdiff_plain;h=4a9c7bbe2ed4d2b240674b1fb606c41d3940c412;p=linux-2.6-microblaze.git bpf: Resolve to prog->aux->dst_prog->type only for BPF_PROG_TYPE_EXT The commit 7e40781cc8b7 ("bpf: verifier: Use target program's type for access verifications") fixes the verifier checking for BPF_PROG_TYPE_EXT (extension) prog such that the verifier looks for things based on the target prog type that it is extending instead of the BPF_PROG_TYPE_EXT itself. The current resolve_prog_type() returns the target prog type. It checks for nullness on prog->aux->dst_prog. However, when loading a BPF_PROG_TYPE_TRACING prog and it is tracing another bpf prog instead of a kernel function, prog->aux->dst_prog is not NULL also. In this case, the verifier should still verify as the BPF_PROG_TYPE_TRACING type instead of the traced prog type in prog->aux->dst_prog->type. An oops has been reported when tracing a struct_ops prog. A NULL dereference happened in check_return_code() when accessing the prog->aux->attach_func_proto->type and prog->aux->attach_func_proto is NULL here because the traced struct_ops prog has the "unreliable" set. This patch is to change the resolve_prog_type() to only return the target prog type if the prog being verified is BPF_PROG_TYPE_EXT. Fixes: 7e40781cc8b7 ("bpf: verifier: Use target program's type for access verifications") Signed-off-by: Martin KaFai Lau Signed-off-by: Alexei Starovoitov Acked-by: Yonghong Song Link: https://lore.kernel.org/bpf/20220330011456.2984509-1-kafai@fb.com --- diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index c1fc4af47f69..3a9d2d7cc6b7 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -570,9 +570,11 @@ static inline u32 type_flag(u32 type) return type & ~BPF_BASE_TYPE_MASK; } +/* only use after check_attach_btf_id() */ static inline enum bpf_prog_type resolve_prog_type(struct bpf_prog *prog) { - return prog->aux->dst_prog ? prog->aux->dst_prog->type : prog->type; + return prog->type == BPF_PROG_TYPE_EXT ? + prog->aux->dst_prog->type : prog->type; } #endif /* _LINUX_BPF_VERIFIER_H */