[PATCH v2] xfs: fix possible overflow in xfs_ioc_trim()

[Lukas Czerner]

In xfs_ioc_trim it is possible that start+len might overflow. Fix it by
decrementing the len so that start+len equals to the file system size in
the worst case.

Signed-off-by: Lukas Czerner <lczerner at redhat.com>
---
v2: Use sb_dblocks instead of XFS_MAX_DBLOCKS to get max block count

 fs/xfs/xfs_discard.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/fs/xfs/xfs_discard.c b/fs/xfs/xfs_discard.c
index 244e797..b45e3c9 100644
--- a/fs/xfs/xfs_discard.c
+++ b/fs/xfs/xfs_discard.c
@@ -146,6 +146,7 @@ xfs_ioc_trim(
 	unsigned int		granularity = q->limits.discard_granularity;
 	struct fstrim_range	range;
 	xfs_fsblock_t		start, len, minlen;
+	xfs_fsblock_t		max_blks = mp->m_sb.sb_dblocks;
 	xfs_agnumber_t		start_agno, end_agno, agno;
 	__uint64_t		blocks_trimmed = 0;
 	int			error, last_error = 0;
@@ -171,7 +172,8 @@ xfs_ioc_trim(
 	start_agno = XFS_FSB_TO_AGNO(mp, start);
 	if (start_agno >= mp->m_sb.sb_agcount)
 		return -XFS_ERROR(EINVAL);
-
+	if (len > max_blks)
+		len = max_blks - start;
 	end_agno = XFS_FSB_TO_AGNO(mp, start + len);
 	if (end_agno >= mp->m_sb.sb_agcount)
 		end_agno = mp->m_sb.sb_agcount - 1;
-- 
1.7.4.4