FAILED: patch "[PATCH] ext4: don't fail GETFSUUID when the caller provides a long" 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:

a7e9d977e031 ("ext4: don't fail GETFSUUID when the caller provides a long buffer")
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 a7e9d977e031fceefe1e7cd69ebd7202d5758b56 Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <[email protected]>
Date: Thu, 10 Nov 2022 12:16:34 -0800
Subject: [PATCH] ext4: don't fail GETFSUUID when the caller provides a long
buffer

If userspace provides a longer UUID buffer than is required, we shouldn't fail the call with EINVAL -- rather, we can fill the caller's buffer with the bytes we /can/ fill, and update the length field to reflect what we copied. This doesn't break the UAPI since we're enabling a case that currently fails, and so far Ted hasn't released a version of e2fsprogs that uses the new ext4 ioctl.

index beedaebab21c..202953b5db49 100644
@@ -1160,14 +1160,16 @@ static int ext4_ioctl_getuuid(struct ext4_sb_info *sbi,
 		return 0;
 	}
 
-	if (fsuuid.fsu_len != UUID_SIZE || fsuuid.fsu_flags != 0)
+	if (fsuuid.fsu_len < UUID_SIZE || fsuuid.fsu_flags != 0)
 		return -EINVAL;
 
 	lock_buffer(sbi->s_sbh);
 	memcpy(uuid, sbi->s_es->s_uuid, UUID_SIZE);
 	unlock_buffer(sbi->s_sbh);
 
-	if (copy_to_user(&ufsuuid->fsu_uuid[0], uuid, UUID_SIZE))
+	fsuuid.fsu_len = UUID_SIZE;
+	if (copy_to_user(ufsuuid, &fsuuid, sizeof(fsuuid)) ||
+	    copy_to_user(&ufsuuid->fsu_uuid[0], uuid, UUID_SIZE))
 		return -EFAULT;
 	return 0;
 }