Commit ca04d9c3 authored Aug 26, 2010 by Sage Weil

ceph: fix null pointer deref on anon root dentry release



When we release a root dentry, particularly after a splice, the parent
(actually our) inode was evaluating to NULL and was getting dereferenced
by ceph_snap().  This is reproduced by something as simple as

 mount -t ceph monhost:/a/b mnt
 mount -t ceph monhost:/a mnt2
 ls mnt2

A splice_dentry() would kill the old 'b' inode's root dentry, and we'd
crash while releasing it.

Fix by checking for both the ROOT and NULL cases explicitly.  We only need
to invalidate the parent dir when we have a correct parent to invalidate.

Signed-off-by: Sage Weil <sage@newdream.net>

parent 2bfc96a1

fs/ceph/dir.c

+7 −3

Original line number	Diff line number	Diff line
		@@ -1021,11 +1021,15 @@ static int ceph_d_revalidate(struct dentry dentry, struct nameidata nd)
		static void ceph_dentry_release(struct dentry *dentry)
		{
		struct ceph_dentry_info *di = ceph_dentry(dentry);
		struct inode *parent_inode = dentry->d_parent->d_inode;
		u64 snapid = ceph_snap(parent_inode);
		struct inode *parent_inode = NULL;
		u64 snapid = CEPH_NOSNAP;

		if (!IS_ROOT(dentry)) {
		parent_inode = dentry->d_parent->d_inode;
		if (parent_inode)
		snapid = ceph_snap(parent_inode);
		}
		dout("dentry_release %p parent %p\n", dentry, parent_inode);

		if (parent_inode && snapid != CEPH_SNAPDIR) {
		struct ceph_inode_info *ci = ceph_inode(parent_inode);