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

[Lukas Czerner <lczerner@xxxxxxxxxx>]

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@xxxxxxxxxx>
---
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