From: Nikolay Borisov <kernel@kyup.com>
Date: Mon, 10 Oct 2016 12:38:18 +0000 (+0300)
Subject: ceph: fix error handling in ceph_read_iter
X-Git-Tag: v4.9-rc2~21^2~3
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=0d7718f666be181fda1ba2d08f137d87c1419347;p=linux-block.git

ceph: fix error handling in ceph_read_iter

In case __ceph_do_getattr returns an error and the retry_op in
ceph_read_iter is not READ_INLINE, then it's possible to invoke
__free_page on a page which is NULL, this naturally leads to a crash.
This can happen when, for example, a process waiting on a MDS reply
receives sigterm.

Fix this by explicitly checking whether the page is set or not.

Cc: stable@vger.kernel.org # 3.19+
Signed-off-by: Nikolay Borisov <kernel@kyup.com>
Reviewed-by: Yan, Zheng <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
---

diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 7bf08825cc11..18630e800208 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -1272,7 +1272,8 @@ again:
 		statret = __ceph_do_getattr(inode, page,
 					    CEPH_STAT_CAP_INLINE_DATA, !!page);
 		if (statret < 0) {
-			 __free_page(page);
+			if (page)
+				__free_page(page);
 			if (statret == -ENODATA) {
 				BUG_ON(retry_op != READ_INLINE);
 				goto again;