Commit c6b0b656 authored Dec 15, 2016 by Jeff Layton Committed by Ilya Dryomov Feb 20, 2017

ceph: clean up unsafe d_parent accesses in build_dentry_path

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@redhat.com>
Reviewed-by: Yan, Zheng <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

parent 30c71233

fs/ceph/mds_client.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -1800,13 +1800,18 @@ 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);

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