From: Darrick J. Wong <djwong@xxxxxxxxxx> commit b76abb5157468756163fe7e3431c9fe32cba57ca upstream. 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@xxxxxxxxxx> Reviewed-by: Catherine Hoang <catherine.hoang@xxxxxxxxxx> Link: https://lore.kernel.org/r/166811138914.327006.9241306894437166566.stgit@magnolia Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> Cc: stable@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/ext4/ioctl.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/fs/ext4/ioctl.c +++ b/fs/ext4/ioctl.c @@ -1154,9 +1154,10 @@ static int ext4_ioctl_getuuid(struct ext 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)
