The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 4a9c7bbe2ed4d2b240674b1fb606c41d3940c412 Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau kafai@fb.com Date: Tue, 29 Mar 2022 18:14:56 -0700 Subject: [PATCH] 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 kafai@fb.com Signed-off-by: Alexei Starovoitov ast@kernel.org Acked-by: Yonghong Song yhs@fb.com 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 */