linux-kernel - [PATCH] libbpf: increase probe_name buffer size to avoid format-truncation

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Message-ID: <20250917124334.1783090-1-quic_ckantibh@quicinc.com>
Date: Wed, 17 Sep 2025 18:13:34 +0530
From: Sanjay Chitroda <quic_ckantibh@...cinc.com>
To: Alexei Starovoitov <ast@...nel.org>,
        Sanjay Chitroda
	<sanjayembeddese@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii
 Nakryiko <andrii@...nel.org>
CC: Martin KaFai Lau <martin.lau@...ux.dev>,
        Eduard Zingerman
	<eddyz87@...il.com>, Song Liu <song@...nel.org>,
        Yonghong Song
	<yonghong.song@...ux.dev>,
        John Fastabend <john.fastabend@...il.com>,
        KP
 Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>,
        Hao Luo
	<haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        <bpf@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] libbpf: increase probe_name buffer size to avoid format-truncation

This patch increases the size of the `probe_name` buffer in
`probe_kern_syscall_wrapper()` from `MAX_EVENT_NAME_LEN` to
`MAX_EVENT_NAME_LEN * 2`.

The change addresses a build failure in perf builds caused by GCC's
-Werror=format-truncation warning:

  libbpf.c:11052:45: error: '%s' directive output may be truncated writing up to 63 bytes into a region of size between 34 and 53 [-Werror=format-truncation]

The warning is triggered by a `snprintf()` call that formats a string
using syscall names and other identifiers. In some cases, the buffer
size is insufficient, leading to potential truncation.

Debug builds pass because they do not treat warnings as errors, but
perf builds fail due to `-Werror`.

Increasing the buffer size ensures that the formatted string fits
safely, resolving the issue without affecting functionality.

Signed-off-by: Sanjay Chitroda <quic_ckantibh@...cinc.com>
---
 tools/lib/bpf/libbpf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 8f5a81b672e1..9413e86476da 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -11290,7 +11290,7 @@ int probe_kern_syscall_wrapper(int token_fd)
 
 		return pfd >= 0 ? 1 : 0;
 	} else { /* legacy mode */
-		char probe_name[MAX_EVENT_NAME_LEN];
+		char probe_name[MAX_EVENT_NAME_LEN * 2];
 
 		gen_probe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0);
 		if (add_kprobe_event_legacy(probe_name, false, syscall_name, 0) < 0)
-- 
2.34.1