Patch "ceph: fix race during filling readdir cache" has been added to the 4.4-stable tree

Patch "ceph: fix race during filling readdir cache" has been added to the 4.4-stable tree

[gregkh]

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

    ceph: fix race during filling readdir cache

to the 4.4-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:
     ceph-fix-race-during-filling-readdir-cache.patch
and it can be found in the queue-4.4 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 af5e5eb574776cdf1b756a27cc437bff257e22fe Mon Sep 17 00:00:00 2001
From: "Yan, Zheng" <zyan@redhat.com>
Date: Fri, 26 Feb 2016 16:27:13 +0800
Subject: ceph: fix race during filling readdir cache

From: Yan, Zheng <zyan@redhat.com>

commit af5e5eb574776cdf1b756a27cc437bff257e22fe upstream.

Readdir cache uses page cache to save dentry pointers. When adding
dentry pointers to middle of a page, we need to make sure the page
already exists. Otherwise the beginning part of the page will be
invalid pointers.

Signed-off-by: Yan, Zheng <zyan@redhat.com>
Cc: Nikolay Borisov <kernel@kyup.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/ceph/inode.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -1358,15 +1358,20 @@ static int fill_readdir_cache(struct ino
 
 	if (!ctl->page || pgoff != page_index(ctl->page)) {
 		ceph_readdir_cache_release(ctl);
-		ctl->page  = grab_cache_page(&dir->i_data, pgoff);
+		if (idx == 0)
+			ctl->page = grab_cache_page(&dir->i_data, pgoff);
+		else
+			ctl->page = find_lock_page(&dir->i_data, pgoff);
 		if (!ctl->page) {
 			ctl->index = -1;
-			return -ENOMEM;
+			return idx == 0 ? -ENOMEM : 0;
 		}
 		/* reading/filling the cache are serialized by
 		 * i_mutex, no need to use page lock */
 		unlock_page(ctl->page);
 		ctl->dentries = kmap(ctl->page);
+		if (idx == 0)
+			memset(ctl->dentries, 0, PAGE_CACHE_SIZE);
 	}
 
 	if (req->r_dir_release_cnt == atomic64_read(&ci->i_release_count) &&


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

queue-4.4/ceph-fix-race-during-filling-readdir-cache.patch