affs_lookup(): close a race with affs_remove_link()

commit 30da870ce4a4e007c901858a96e9e394a1daa74a upstream.

we unlock the directory hash too early - if we are looking at secondary
link and primary (in another directory) gets removed just as we unlock,
we could have the old primary moved in place of the secondary, leaving
us to look into freed entry (and leaving our dentry with ->d_fsdata
pointing to a freed entry).

Cc: stable@vger.kernel.org # 2.4.4+
Acked-by: David Sterba <dsterba@suse.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/affs/namei.c b/fs/affs/namei.c
index 181e05b..92448d0 100644 (file)
--- a/fs/affs/namei.c
+++ b/fs/affs/namei.c
@@ -224,9 +224,10 @@ affs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
 
        affs_lock_dir(dir);
        bh = affs_find_entry(dir, dentry);
-       affs_unlock_dir(dir);
-       if (IS_ERR(bh))
+       if (IS_ERR(bh)) {
+               affs_unlock_dir(dir);
                return ERR_CAST(bh);
+       }
        if (bh) {
                u32 ino = bh->b_blocknr;
 
@@ -240,10 +241,13 @@ affs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
                }
                affs_brelse(bh);
                inode = affs_iget(sb, ino);
-               if (IS_ERR(inode))
+               if (IS_ERR(inode)) {
+                       affs_unlock_dir(dir);
                        return ERR_CAST(inode);
+               }
        }
        d_add(dentry, inode);
+       affs_unlock_dir(dir);
        return NULL;
 }