Patch "fuse: fix fuse_write_end() if zero bytes were copied" has been added to the 4.8-stable tree

Patch "fuse: fix fuse_write_end() if zero bytes were copied" has been added to the 4.8-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    fuse: fix fuse_write_end() if zero bytes were copied

to the 4.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     fuse-fix-fuse_write_end-if-zero-bytes-were-copied.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 59c3b76cc61d1d676f965c192cc7969aa5cb2744 Mon Sep 17 00:00:00 2001
From: Miklos Szeredi <mszeredi@redhat.com>
Date: Thu, 18 Aug 2016 09:10:44 +0200
Subject: fuse: fix fuse_write_end() if zero bytes were copied

From: Miklos Szeredi <mszeredi@redhat.com>

commit 59c3b76cc61d1d676f965c192cc7969aa5cb2744 upstream.

If pos is at the beginning of a page and copied is zero then page is not
zeroed but is marked uptodate.

Fix by skipping everything except unlock/put of page if zero bytes were
copied.

Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Fixes: 6b12c1b37e55 ("fuse: Implement write_begin/write_end callbacks")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/fuse/file.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1985,6 +1985,10 @@ static int fuse_write_end(struct file *f
 {
 	struct inode *inode = page->mapping->host;
 
+	/* Haven't copied anything?  Skip zeroing, size extending, dirtying. */
+	if (!copied)
+		goto unlock;
+
 	if (!PageUptodate(page)) {
 		/* Zero any unwritten bytes at the end of the page */
 		size_t endoff = (pos + copied) & ~PAGE_MASK;
@@ -1995,6 +1999,8 @@ static int fuse_write_end(struct file *f
 
 	fuse_write_update_size(inode, pos + copied);
 	set_page_dirty(page);
+
+unlock:
 	unlock_page(page);
 	put_page(page);
 


Patches currently in stable-queue which might be from mszeredi@redhat.com are

queue-4.8/fuse-fix-fuse_write_end-if-zero-bytes-were-copied.patch