[PATCH v5 4/9] xfs: clamp a pNFS LAYOUTCOMMIT extent before computing its end

[Daejun Park via B4 Relay]

From: Daejun Park <daejun7.park@xxxxxxxxxxx>

xfs_fs_commit_blocks() adds the client's length to the offset before it
clamps the end to the file size. A large length wraps the sum and
reaches xfs_iomap_write_unwritten() unclamped. With the previous two
patches the LAYOUTCOMMIT then fails with -EIO and converts nothing.

Clamp the length first.

Fixes: 527851124d10 ("xfs: implement pNFS export operations")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Daejun Park <daejun7.park@xxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Pankaj Raghav <p.raghav@xxxxxxxxxxx>
---
Tested with pynfs: a LAYOUTCOMMIT of 2^64 - 4 KiB at 4 KiB got
NFS4ERR_IO and a WARNING. Now it converts up to the hole, then fails.
---
 fs/xfs/xfs_pnfs.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/xfs/xfs_pnfs.c b/fs/xfs/xfs_pnfs.c
index 7ff83274a5..19eb18e129 100644
--- a/fs/xfs/xfs_pnfs.c
+++ b/fs/xfs/xfs_pnfs.c
@@ -328,9 +328,7 @@ xfs_fs_commit_blocks(
 		if (start > size)
 			continue;
 
-		end = start + maps[i].length;
-		if (end > size)
-			end = size;
+		end = start + min_t(u64, maps[i].length, size - start);
 
 		length = end - start;
 		if (!length)

-- 
2.43.0