linux-kernel - [PATCH 4.4 52/58] nfs_write_end(): fix handling of short copies

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Message-Id: <20170106213909.018442161@linuxfoundation.org>
Date:   Fri,  6 Jan 2017 22:44:37 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH 4.4 52/58] nfs_write_end(): fix handling of short copies

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Al Viro <viro@...iv.linux.org.uk>

commit c0cf3ef5e0f47e385920450b245d22bead93e7ad upstream.

What matters when deciding if we should make a page uptodate is
not how much we _wanted_ to copy, but how much we actually have
copied.  As it is, on architectures that do not zero tail on
short copy we can leave uninitialized data in page marked uptodate.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/nfs/file.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -407,7 +407,7 @@ static int nfs_write_end(struct file *fi
 	 */
 	if (!PageUptodate(page)) {
 		unsigned pglen = nfs_page_length(page);
-		unsigned end = offset + len;
+		unsigned end = offset + copied;
 
 		if (pglen == 0) {
 			zero_user_segments(page, 0, offset,