From: Darrick J. Wong <darrick.wong@oracle.com>
Date: Mon, 29 Oct 2018 23:40:39 +0000 (+1100)
Subject: vfs: exit early from zero length remap operations
X-Git-Tag: v4.20-rc1~23^2~25
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2c5773f102c9bb07d5328467f61f0a88f2f2892d;p=thirdparty%2Fkernel%2Flinux.git

vfs: exit early from zero length remap operations

If a remap caller asks us to remap to the source file's EOF and the
source file length leaves us with a zero byte request, exit early.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>
---

diff --git a/fs/read_write.c b/fs/read_write.c
index d6e8e242a15fa..2456da3f8a414 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1748,6 +1748,8 @@ int vfs_clone_file_prep(struct file *file_in, loff_t pos_in,
 		if (pos_in > isize)
 			return -EINVAL;
 		*len = isize - pos_in;
+		if (*len == 0)
+			return 0;
 	}
 
 	/* Check that we don't violate system file offset limits. */