[XFS] Really fix use after free in xfs_iunpin.

The previous attempts to fix the linux inode use-after-free in xfs_iunpin
simply made the problem harder to hit. We actually need complete exclusion
between xfs_reclaim and xfs_iunpin, as well as ensuring that the i_flags
are consistent during both of these functions. Introduce a new spinlock
for exclusion and the i_flags, and fix up xfs_iunpin to use igrab before
marking the inode dirty.

SGI-PV: 952967
SGI-Modid: xfs-linux-melb:xfs-kern:26964a

Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Tim Shimmin <tes@sgi.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index 9df9ed37d219..38c4d128a8c0 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -227,7 +227,9 @@ xfs_initialize_vnode(
                 xfs_revalidate_inode(XFS_BHVTOM(bdp), vp, ip);
                 xfs_set_inodeops(inode);
 
+                spin_lock(&ip->i_flags_lock);
                 ip->i_flags &= ~XFS_INEW;
+                spin_unlock(&ip->i_flags_lock);
                 barrier();
 
                 unlock_new_inode(inode);