This is a note to let you know that I've just added the patch titled
ceph: clean up unsafe d_parent accesses in build_dentry_path
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-clean-up-unsafe-d_parent-accesses-in-build_dentry_path.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@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Thu Oct 19 15:15:46 CEST 2017
From: Jeff Layton <jlayton@xxxxxxxxxx>
Date: Thu, 15 Dec 2016 08:37:57 -0500
Subject: ceph: clean up unsafe d_parent accesses in build_dentry_path
From: Jeff Layton <jlayton@xxxxxxxxxx>
[ Upstream commit c6b0b656ca24ede6657abb4a2cd910fa9c1879ba ]
While we hold a reference to the dentry when build_dentry_path is
called, we could end up racing with a rename that changes d_parent.
Handle that situation correctly, by using the rcu_read_lock to
ensure that the parent dentry and inode stick around long enough
to safely check ceph_snap and ceph_ino.
Link: http://tracker.ceph.com/issues/18148
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
Reviewed-by: Yan, Zheng <zyan@xxxxxxxxxx>
Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/ceph/mds_client.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -1845,13 +1845,18 @@ static int build_dentry_path(struct dent
int *pfreepath)
{
char *path;
+ struct inode *dir;
- if (ceph_snap(d_inode(dentry->d_parent)) == CEPH_NOSNAP) {
- *pino = ceph_ino(d_inode(dentry->d_parent));
+ rcu_read_lock();
+ dir = d_inode_rcu(dentry->d_parent);
+ if (dir && ceph_snap(dir) == CEPH_NOSNAP) {
+ *pino = ceph_ino(dir);
+ rcu_read_unlock();
*ppath = dentry->d_name.name;
*ppathlen = dentry->d_name.len;
return 0;
}
+ rcu_read_unlock();
path = ceph_mdsc_build_path(dentry, ppathlen, pino, 1);
if (IS_ERR(path))
return PTR_ERR(path);
Patches currently in stable-queue which might be from jlayton@xxxxxxxxxx are
queue-4.4/ceph-clean-up-unsafe-d_parent-accesses-in-build_dentry_path.patch