xfs: limit entries returned when counting fsmap records

[ Upstream commit acd1ac3aa22fd58803a12d26b1ab7f70232f8d8d ]

If userspace asked fsmap to count the number of entries, we cannot
return more than UINT_MAX entries because fmh_entries is u32.
Therefore, stop counting if we hit this limit or else we will waste time
to return truncated results.

Fixes: e89c041338ed ("xfs: implement the GETFSMAP ioctl")
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
index 43cfc07996a43ed1779e7ce6249df2113d87dc28..e7622e0841868daba1a5cef66e4def18c0e7b539 100644 (file)
--- a/fs/xfs/xfs_fsmap.c
+++ b/fs/xfs/xfs_fsmap.c
@@ -273,6 +273,9 @@ xfs_getfsmap_helper(
 
        /* Are we just counting mappings? */
        if (info->head->fmh_count == 0) {
+               if (info->head->fmh_entries == UINT_MAX)
+                       return -ECANCELED;
+
                if (rec_daddr > info->next_daddr)
                        info->head->fmh_entries++;