From: Darrick J. Wong <djwong@xxxxxxxxxx> commit a7e9d977e031fceefe1e7cd69ebd7202d5758b56 upstream. 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. Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx> Reviewed-by: Catherine Hoang <catherine.hoang@xxxxxxxxxx> Link: https://lore.kernel.org/r/166811139478.327006.13879198441587445544.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 | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/fs/ext4/ioctl.c +++ b/fs/ext4/ioctl.c @@ -1159,14 +1159,16 @@ static int ext4_ioctl_getuuid(struct ext return -EINVAL; } - 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; }
