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Commit bd530852 authored by Jeff Layton's avatar Jeff Layton Committed by Greg Kroah-Hartman
Browse files

ceph: clean up unsafe d_parent accesses in build_dentry_path 


[ 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: default avatarJeff Layton <jlayton@redhat.com>
Reviewed-by: default avatarYan, Zheng <zyan@redhat.com>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 6839ad59

fs/ceph/mds_client.c

+7 −2
Original line number Diff line number Diff line
@@ -1782,13 +1782,18 @@ static int build_dentry_path(struct dentry *dentry, 
			     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);