From: Thorsten Blum <thorsten.blum@linux.dev>
Date: Wed, 13 Aug 2025 13:32:18 +0000 (-0400)
Subject: smb: server: Fix extension string in ksmbd_extract_shortname()
X-Git-Tag: v5.15.190~123
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=26eb63f732b09f48b539ae272853fa890aec9103;p=thirdparty%2Fkernel%2Fstable.git

smb: server: Fix extension string in ksmbd_extract_shortname()

[ Upstream commit 8e7d178d06e8937454b6d2f2811fa6a15656a214 ]

In ksmbd_extract_shortname(), strscpy() is incorrectly called with the
length of the source string (excluding the NUL terminator) rather than
the size of the destination buffer. This results in "__" being copied
to 'extension' rather than "___" (two underscores instead of three).

Use the destination buffer size instead to ensure that the string "___"
(three underscores) is copied correctly.

Cc: stable@vger.kernel.org
Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3")
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/fs/ksmbd/smb_common.c b/fs/ksmbd/smb_common.c
index e90a1e8c1951d..0438a634f4c21 100644
--- a/fs/ksmbd/smb_common.c
+++ b/fs/ksmbd/smb_common.c
@@ -508,7 +508,7 @@ int ksmbd_extract_shortname(struct ksmbd_conn *conn, const char *longname,
 
 	p = strrchr(longname, '.');
 	if (p == longname) { /*name starts with a dot*/
-		strscpy(extension, "___", strlen("___"));
+		strscpy(extension, "___", sizeof(extension));
 	} else {
 		if (p) {
 			p++;