FAILED: patch "[PATCH] ext4: dont return EINVAL from GETFSUUID when reporting UUID" failed to apply to 4.19-stable tree

The patch below does not apply to the 4.19-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 <[email protected]>.

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")
351a0a3fbc35 ("ext4: add ioctl EXT4_IOC_CHECKPOINT")
4db5c2e6236f ("ext4: convert to fileattr")
7d6beb71da3c ("Merge tag 'idmapped-mounts-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux")

thanks,

greg k-h

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

From b76abb5157468756163fe7e3431c9fe32cba57ca Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <[email protected]>
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.

index e5f60057db5b..beedaebab21c 100644
@@ -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)