[PATCH 6.6.y] xfs: fix integer overflow in bmap intent sort comparator

[Sasha Levin <sashal@kernel.org>]

From: Long Li <leo.lilong@huawei.com>

[ Upstream commit 362c490980867930a098b99f421268fbd7ca05fd ]

xfs_bmap_update_diff_items() sorts bmap intents by inode number using
a subtraction of two xfs_ino_t (uint64_t) values, with the result
truncated to int. This is incorrect when two inode numbers differ by
more than INT_MAX (2^31 - 1), which is entirely possible on large XFS
filesystems.

Fix this by replacing the subtraction with cmp_int().

Cc: <stable@vger.kernel.org> # v4.9
Fixes: 9f3afb57d5f1 ("xfs: implement deferred bmbt map/unmap operations")
Signed-off-by: Long Li <leo.lilong@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
[ replaced `bi_entry()` macro with `container_of()` and inlined `cmp_int()` as a manual three-way comparison expression ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/xfs/xfs_bmap_item.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_bmap_item.c b/fs/xfs/xfs_bmap_item.c
index b6d63b8bdad5a..969cad575c302 100644
--- a/fs/xfs/xfs_bmap_item.c
+++ b/fs/xfs/xfs_bmap_item.c
@@ -278,7 +278,8 @@ xfs_bmap_update_diff_items(
 
 	ba = container_of(a, struct xfs_bmap_intent, bi_list);
 	bb = container_of(b, struct xfs_bmap_intent, bi_list);
-	return ba->bi_owner->i_ino - bb->bi_owner->i_ino;
+	return (ba->bi_owner->i_ino > bb->bi_owner->i_ino) -
+		(ba->bi_owner->i_ino < bb->bi_owner->i_ino);
 }
 
 /* Set the map extent flags for this mapping. */
-- 
2.51.0