FAILED: patch "[PATCH] ext4: dont return EINVAL from GETFSUUID when reporting UUID" failed to apply to 5.15-stable tree

[<gregkh@linuxfoundation.org>]

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@vger.kernel.org>.

Possible dependencies:

b76abb515746 ("ext4: dont return EINVAL from GETFSUUID when reporting UUID length")
d95efb14c0b8 ("ext4: add ioctls to get/set the ext4 superblock uuid")
bbc605cdb1e1 ("ext4: implement support for get/set fs label")

thanks,

greg k-h

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

From b76abb5157468756163fe7e3431c9fe32cba57ca Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <djwong@kernel.org>
Date: Thu, 10 Nov 2022 12:16:29 -0800
Subject: [PATCH] ext4: dont return EINVAL from GETFSUUID when reporting UUID
 length

If userspace calls this ioctl with fsu_length (the length of the
fsuuid.fsu_uuid array) set to zero, ext4 copies the desired uuid length
out to userspace.  The kernel call returned a result from a valid input,
so the return value here should be zero, not EINVAL.

While we're at it, fix the copy_to_user call to make it clear that we're
only copying out fsu_len.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Catherine Hoang <catherine.hoang@oracle.com>
Link: https://lore.kernel.org/r/166811138914.327006.9241306894437166566.stgit@magnolia
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org

diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index e5f60057db5b..beedaebab21c 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -1154,9 +1154,10 @@ static int ext4_ioctl_getuuid(struct ext4_sb_info *sbi,
 
 	if (fsuuid.fsu_len == 0) {
 		fsuuid.fsu_len = UUID_SIZE;
-		if (copy_to_user(ufsuuid, &fsuuid, sizeof(fsuuid.fsu_len)))
+		if (copy_to_user(&ufsuuid->fsu_len, &fsuuid.fsu_len,
+					sizeof(fsuuid.fsu_len)))
 			return -EFAULT;
-		return -EINVAL;
+		return 0;
 	}
 
 	if (fsuuid.fsu_len != UUID_SIZE || fsuuid.fsu_flags != 0)