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Message-ID: <20250904121757.1679560-1-m.semenov@tssltd.ru>
Date: Thu,  4 Sep 2025 15:17:54 +0300
From: Makar Semyonov <m.semenov@...ltd.ru>
To: Steve French <sfrench@...ba.org>
Cc: Makar Semyonov <m.semenov@...ltd.ru>,
	Paulo Alcantara <pc@...guebit.com>,
	Ronnie Sahlberg <ronniesahlberg@...il.com>,
	Shyam Prasad N <sprasad@...rosoft.com>,
	Tom Talpey <tom@...pey.com>,
	Bharath SM <bharathsm@...rosoft.com>,
	linux-cifs@...r.kernel.org,
	samba-technical@...ts.samba.org,
	linux-kernel@...r.kernel.org
Subject: 

Date: Thu, 4 Sep 2025 15:00:27 +0300
Subject: [PATCH] cifs: prevent NULL pointer dereference in UTF16
 conversion

There can be a NULL pointer dereference bug here. NULL is passed to
__cifs_sfu_make_node without checks, which passes it unchecked to
cifs_strndup_to_utf16, which in turn passes it to
cifs_local_to_utf16_bytes where '*from' is dereferenced, causing a crash.

This patch adds a check for NULL 'src' in cifs_strndup_to_utf16 and
returns NULL early to prevent dereferencing NULL pointer.

Found by Linux Verification Center (linuxtesting.org) with SVACE

Signed-off-by: Makar Semyonov <m.semenov@...ltd.ru>
---
 fs/smb/client/cifs_unicode.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/smb/client/cifs_unicode.c b/fs/smb/client/cifs_unicode.c
index 4cc6e0896fad..1a9324bec7d6 100644
--- a/fs/smb/client/cifs_unicode.c
+++ b/fs/smb/client/cifs_unicode.c
@@ -628,6 +628,9 @@ cifs_strndup_to_utf16(const char *src, const int maxlen, int *utf16_len,
 {
 	int len;
 	__le16 *dst;
+
+	if (!src)
+		return NULL;

 	len = cifs_local_to_utf16_bytes(src, maxlen, cp);
 	len += 2; /* NULL */
-- 
2.43.0