FAILED: patch "[PATCH] smb: client: fix potential NULL deref in" failed to apply to 5.15-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

The patch below does not apply to the 5.15-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@xxxxxxxxxxxxxxx>.

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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 92414333eb375ed64f4ae92d34d579e826936480
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2023121138-alias-goofiness-2060@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

92414333eb37 ("smb: client: fix potential NULL deref in parse_dfs_referrals()")

thanks,

greg k-h

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

>From 92414333eb375ed64f4ae92d34d579e826936480 Mon Sep 17 00:00:00 2001
From: Paulo Alcantara <pc@xxxxxxxxxxxxx>
Date: Tue, 5 Dec 2023 21:49:29 -0300
Subject: [PATCH] smb: client: fix potential NULL deref in
 parse_dfs_referrals()

If server returned no data for FSCTL_DFS_GET_REFERRALS, @dfs_rsp will
remain NULL and then parse_dfs_referrals() will dereference it.

Fix this by returning -EIO when no output data is returned.

Besides, we can't fix it in SMB2_ioctl() as some FSCTLs are allowed to
return no data as per MS-SMB2 2.2.32.

Fixes: 9d49640a21bf ("CIFS: implement get_dfs_refer for SMB2+")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Robert Morris <rtm@xxxxxxxxxxxxx>
Signed-off-by: Paulo Alcantara (SUSE) <pc@xxxxxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>

diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index 45931115f475..fcfb6566b899 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -2836,6 +2836,8 @@ smb2_get_dfs_refer(const unsigned int xid, struct cifs_ses *ses,
 		usleep_range(512, 2048);
 	} while (++retry_count < 5);
 
+	if (!rc && !dfs_rsp)
+		rc = -EIO;
 	if (rc) {
 		if (!is_retryable_error(rc) && rc != -ENOENT && rc != -EOPNOTSUPP)
 			cifs_tcon_dbg(VFS, "%s: ioctl error: rc=%d\n", __func__, rc);