linux-kernel - [PATCH] bpf: fix uninit-value in strnchr

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Message-ID: <tencent_AABA5D95191FCFD28DB325F58D8212525D07@qq.com>
Date: Tue,  9 Apr 2024 19:37:43 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+9b8be5e35747291236c8@...kaller.appspotmail.com
Cc: andrii@...nel.org,
	ast@...nel.org,
	bpf@...r.kernel.org,
	daniel@...earbox.net,
	haoluo@...gle.com,
	john.fastabend@...il.com,
	jolsa@...nel.org,
	kpsingh@...nel.org,
	linux-kernel@...r.kernel.org,
	martin.lau@...ux.dev,
	sdf@...gle.com,
	song@...nel.org,
	syzkaller-bugs@...glegroups.com,
	yonghong.song@...ux.dev
Subject: [PATCH] bpf: fix uninit-value in strnchr

According to the context in bpf_bprintf_prepare(), this is checking if fmt ends
with a NUL word. Therefore, strnchrnul() should be used for validation instead
of strnchr().

Reported-by: syzbot+9b8be5e35747291236c8@...kaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@...com>
---
 kernel/bpf/helpers.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 449b9a5d3fe3..07490eba24fe 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -826,7 +826,7 @@ int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args,
 	u64 cur_arg;
 	char fmt_ptype, cur_ip[16], ip_spec[] = "%pXX";
 
-	fmt_end = strnchr(fmt, fmt_size, 0);
+	fmt_end = strnchrnul(fmt, fmt_size, 0);
 	if (!fmt_end)
 		return -EINVAL;
 	fmt_size = fmt_end - fmt;
-- 
2.43.0