xfs: check for possible overflow in xfs_ioc_trim

If range.start or range.minlen is bigger than filesystem size, return
invalid value error. This fixes possible overflow in BTOBB macro when
passed value was nearly ULLONG_MAX.
Signed-off-by: Tomas Racek <tracek@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

fs/xfs/xfs_discard.c

@@ -179,12 +179,14 @@ xfs_ioc_trim(
 	 * used by the fstrim application.  In the end it really doesn't
 	 * matter as trimming blocks is an advisory interface.
 	 */
+	if (range.start >= XFS_FSB_TO_B(mp, mp->m_sb.sb_dblocks) ||
+	    range.minlen > XFS_FSB_TO_B(mp, XFS_ALLOC_AG_MAX_USABLE(mp)))
+		return -XFS_ERROR(EINVAL);
+
 	start = BTOBB(range.start);
 	end = start + BTOBBT(range.len) - 1;
 	minlen = BTOBB(max_t(u64, granularity, range.minlen));
 
-	if (XFS_BB_TO_FSB(mp, start) >= mp->m_sb.sb_dblocks)
-		return -XFS_ERROR(EINVAL);
 	if (end > XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks) - 1)
 		end = XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks)- 1;