FAILED: patch "[PATCH] smb: server: size directory name conversion buffer correctly" failed to apply to 6.1-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x f1f37834eaba5904103af1f18afe3510c7e9dc71
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026110424-hypnoses-average-6482@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f1f37834eaba5904103af1f18afe3510c7e9dc71 Mon Sep 17 00:00:00 2001
From: VeroFess <coderzeng@hotmail.com>
Date: Mon, 26 Oct 2026 15:01:03 +0900
Subject: [PATCH] smb: server: size directory name conversion buffer correctly

A 2048-byte ASCII directory name needs 4098 bytes when converted to
UTF-16, including the terminator. ksmbd_convert_dir_info_name() caps
its allocation at PATH_MAX and writes past the end of that buffer.

Allocate space for one UTF-16 code unit per input byte plus the
terminator. Use kmalloc_array() to check the size calculation.

Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3")
Cc: stable@vger.kernel.org
Assisted-by: gpt 6 sol with daybreak blue
Signed-off-by: VeroFess <coderzeng@hotmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

diff --git a/fs/smb/server/misc.c b/fs/smb/server/misc.c
index 2dd91c9e956a..5037f37c9226 100644
--- a/fs/smb/server/misc.c
+++ b/fs/smb/server/misc.c
@@ -296,12 +296,13 @@ char *ksmbd_convert_dir_info_name(struct ksmbd_dir_info *d_info,
 				  int *conv_len)
 {
 	char *conv;
-	int  sz = min(4 * d_info->name_len, PATH_MAX);
 
-	if (!sz)
+	if (d_info->name_len <= 0)
 		return NULL;
 
-	conv = kmalloc(sz, KSMBD_DEFAULT_GFP);
+	/* One UTF-16 code unit per input byte, plus the terminating NUL. */
+	conv = kmalloc_array((size_t)d_info->name_len + 1,
+			     sizeof(__le16), KSMBD_DEFAULT_GFP);
 	if (!conv)
 		return NULL;
 
@@ -310,7 +311,6 @@ char *ksmbd_convert_dir_info_name(struct ksmbd_dir_info *d_info,
 				      d_info->name_len, local_nls, 0);
 	*conv_len *= 2;
 
-	/* We allocate buffer twice bigger than needed. */
 	conv[*conv_len] = 0x00;
 	conv[*conv_len + 1] = 0x00;
 	return conv;