linux-kernel - Re: [syzbot] [bpf?] KMSAN: uninit-value in strnchr

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Date: Tue,  9 Apr 2024 21:13:23 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+9b8be5e35747291236c8@...kaller.appspotmail.com
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bpf?] KMSAN: uninit-value in strnchr

please test uini in strnchr

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 04b8076df253

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 449b9a5d3fe3..54abc67c48c7 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -826,7 +826,8 @@ 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);
+	kmsan_unpoison_memory(fmt, fmt_size);
+	fmt_end = strnchrnul(fmt, fmt_size, 0);
 	if (!fmt_end)
 		return -EINVAL;
 	fmt_size = fmt_end - fmt;
-- 
2.43.0