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 7bf08825cc1107a20842533fd93b4f2c2d128577..18630e80020809f18a6a534b2a88249bfa81bd80 100644 (file)
--- 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;