[PATCH v2] xfs: avoid underflow in xfs_ioc_trim()

[Lukas Czerner <lczerner@xxxxxxxxxx>]

Currently if len argument in xfs_ioc_trim() is smaller than one FSB
the 'end' variable underflow. Avoid that by returning EINVAL when
range is smaller than FSB.

Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
---
v2: reworked, return EINVAL if len < FSB

 fs/xfs/xfs_discard.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/fs/xfs/xfs_discard.c b/fs/xfs/xfs_discard.c
index 69cf4fc..04ddbbb 100644
--- a/fs/xfs/xfs_discard.c
+++ b/fs/xfs/xfs_discard.c
@@ -180,7 +180,8 @@ xfs_ioc_trim(
         * 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)))
+           range.minlen > XFS_FSB_TO_B(mp, XFS_ALLOC_AG_MAX_USABLE(mp)) ||
+           range.len < XFS_FSB_TO_B(mp, 1))
                return -XFS_ERROR(EINVAL);
 
        start = BTOBB(range.start);
-- 
1.7.7.6