From: Darrick J. Wong <redacted>

Don't let the iomap callback get away with feeding us a garbage zero
length mapping -- there was a bug in xfs that resulted in those leaking
out to hilarious effect.

Signed-off-by: Darrick J. Wong <redacted>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/iomap.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/iomap.c b/fs/iomap.c
index e5de772..aec35a0 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c

@@ -63,7 +63,7 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
 	ret = ops->iomap_begin(inode, pos, length, flags, &iomap);
 	if (ret)
 		return ret;
-	if (WARN_ON(iomap.offset > pos))
+	if (WARN_ON(iomap.offset > pos) || WARN_ON(iomap.length == 0))
 		return -EIO;
 
 	/*