[PATCH] fuse: fix dereferencing dentry parent

There's no locking for ->d_revalidate, so fuse_dentry_revalidate() should use
dget_parent() instead of simply dereferencing ->d_parent.

Due to topology changes in the directory tree the parent could become negative
or be destroyed while being used.  There hasn't been any reports about this
yet.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 9d0ef5e18740..cfc8f81e60d0 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -138,6 +138,7 @@ static int fuse_dentry_revalidate(struct dentry *entry, struct nameidata *nd)
                 struct fuse_entry_out outarg;
                 struct fuse_conn *fc;
                 struct fuse_req *req;
+                struct dentry *parent;
 
                 /* Doesn't hurt to "reset" the validity timeout */
                 fuse_invalidate_entry_cache(entry);
@@ -151,8 +152,10 @@ static int fuse_dentry_revalidate(struct dentry *entry, struct nameidata *nd)
                 if (IS_ERR(req))
                         return 0;
 
-                fuse_lookup_init(req, entry->d_parent->d_inode, entry, &outarg);
+                parent = dget_parent(entry);
+                fuse_lookup_init(req, parent->d_inode, entry, &outarg);
                 request_send(fc, req);
+                dput(parent);
                 err = req->out.h.error;
                 /* Zero nodeid is same as -ENOENT */
                 if (!err && !outarg.nodeid)