xfs: fix double free of inode

If we fail to initialise the VFS inode in inode_init_always(),
it will call ->delete_inode internally resulting in the inode being
freed. Hence we need to delay the call to inode_init_always()
until after the XFS inode is sufficient set up to handle a
call to ->delete_inode, and then if that fails do not touch
the inode again at all as it has been freed.

Signed-off-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/fs/xfs/xfs_iget.c b/fs/xfs/xfs_iget.c
index 478e587..89b81ee 100644 (file)
--- a/fs/xfs/xfs_iget.c
+++ b/fs/xfs/xfs_iget.c
@@ -69,15 +69,6 @@ xfs_inode_alloc(
        ASSERT(!spin_is_locked(&ip->i_flags_lock));
        ASSERT(completion_done(&ip->i_flush));
 
-       /*
-        * initialise the VFS inode here to get failures
-        * out of the way early.
-        */
-       if (!inode_init_always(mp->m_super, VFS_I(ip))) {
-               kmem_zone_free(xfs_inode_zone, ip);
-               return NULL;
-       }
-
        /* initialise the xfs inode */
        ip->i_ino = ino;
        ip->i_mount = mp;
@@ -113,6 +104,20 @@ xfs_inode_alloc(
 #ifdef XFS_DIR2_TRACE
        ip->i_dir_trace = ktrace_alloc(XFS_DIR2_KTRACE_SIZE, KM_NOFS);
 #endif
+       /*
+       * Now initialise the VFS inode. We do this after the xfs_inode
+       * initialisation as internal failures will result in ->destroy_inode
+       * being called and that will pass down through the reclaim path and
+       * free the XFS inode. This path requires the XFS inode to already be
+       * initialised. Hence if this call fails, the xfs_inode has already
+       * been freed and we should not reference it at all in the error
+       * handling.
+       */
+       if (!inode_init_always(mp->m_super, VFS_I(ip)))
+               return NULL;
+
+       /* prevent anyone from using this yet */
+       VFS_I(ip)->i_state = I_NEW|I_LOCK;
 
        return ip;
 }