[PATCH 4.19 140/264] xfs: limit entries returned when counting fsmap records

[Greg Kroah-Hartman]

From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>

[ 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@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Chandan Babu R <chandanrlinux@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/xfs/xfs_fsmap.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
index 3d76a9e35870a..75b57b683d3e6 100644
--- a/fs/xfs/xfs_fsmap.c
+++ b/fs/xfs/xfs_fsmap.c
@@ -259,6 +259,9 @@ 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++;
 
-- 
2.25.1