linux-kernel - Re: [PATCH RFC 1/5] tracing/probes: Fix to search structure fields correctly

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Date: Sat, 17 Feb 2024 21:27:08 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc: linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org, Steven
 Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH RFC 1/5] tracing/probes: Fix to search structure fields
 correctly

Let me pick this patch because this is a real bugfix.

On Wed, 14 Feb 2024 22:22:23 +0900
"Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:

> From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> 
> Fix to search a field from the structure which has anonymous union
> correctly.
> Since the reference `type` pointer was updated in the loop, the search
> loop suddenly aborted where it hits an anonymous union. Thus it can not
> find the field after the anonymous union. This avoids updating the
> cursor `type` pointer in the loop.
> 
> Fixes: 302db0f5b3d8 ("tracing/probes: Add a function to search a member of a struct/union")
> Cc: stable@...r.kernel.org
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> ---
>  kernel/trace/trace_btf.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/trace/trace_btf.c b/kernel/trace/trace_btf.c
> index ca224d53bfdc..5bbdbcbbde3c 100644
> --- a/kernel/trace/trace_btf.c
> +++ b/kernel/trace/trace_btf.c
> @@ -91,8 +91,8 @@ const struct btf_member *btf_find_struct_member(struct btf *btf,
>  	for_each_member(i, type, member) {
>  		if (!member->name_off) {
>  			/* Anonymous union/struct: push it for later use */
> -			type = btf_type_skip_modifiers(btf, member->type, &tid);
> -			if (type && top < BTF_ANON_STACK_MAX) {
> +			if (btf_type_skip_modifiers(btf, member->type, &tid) &&
> +			    top < BTF_ANON_STACK_MAX) {
>  				anon_stack[top].tid = tid;
>  				anon_stack[top++].offset =
>  					cur_offset + member->offset;
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>