[PATCH bpf] bpf: Fix kprobe_multi cookies access in show_fdinfo callback

[PATCH bpf] bpf: Fix kprobe_multi cookies access in show_fdinfo callback

[Jiri Olsa]

We don't check if cookies are available on the kprobe_multi link
before accessing them in show_fdinfo callback, we should.

Cc: stable@vger.kernel.org
Fixes: da7e9c0a7fbc ("bpf: Add show_fdinfo for kprobe_multi")
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 kernel/trace/bpf_trace.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 9bc0dfd235af..0b040a417442 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2454,8 +2454,10 @@ static void bpf_kprobe_multi_show_fdinfo(const struct bpf_link *link,
 					 struct seq_file *seq)
 {
 	struct bpf_kprobe_multi_link *kmulti_link;
+	bool has_cookies;
 
 	kmulti_link = container_of(link, struct bpf_kprobe_multi_link, link);
+	has_cookies = !!kmulti_link->cookies;
 
 	seq_printf(seq,
 		   "kprobe_cnt:\t%u\n"
@@ -2467,7 +2469,7 @@ static void bpf_kprobe_multi_show_fdinfo(const struct bpf_link *link,
 	for (int i = 0; i < kmulti_link->cnt; i++) {
 		seq_printf(seq,
 			   "%llu\t %pS\n",
-			   kmulti_link->cookies[i],
+			   has_cookies ? kmulti_link->cookies[i] : 0,
 			   (void *)kmulti_link->addrs[i]);
 	}
 }
-- 
2.53.0

Re: [PATCH bpf] bpf: Fix kprobe_multi cookies access in show_fdinfo callback

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Wed, 25 Feb 2026 12:12:49 +0100 you wrote:
> We don't check if cookies are available on the kprobe_multi link
> before accessing them in show_fdinfo callback, we should.
> 
> Cc: stable@vger.kernel.org
> Fixes: da7e9c0a7fbc ("bpf: Add show_fdinfo for kprobe_multi")
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> 
> [...]

Here is the summary with links:
  - [bpf] bpf: Fix kprobe_multi cookies access in show_fdinfo callback
    https://git.kernel.org/bpf/bpf/c/ad6fface76da

You are awesome, thank you!
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