xfs: fix stale inode flush avoidance
When reclaiming stale inodes, we need to guarantee that inodes are
unpinned before returning with a "clean" status. If we don't we can
reclaim inodes that are pinned, leading to use after free in the
transaction subsystem as transactions complete.
Signed-off-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 391d36b..ef77fd8 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -2842,13 +2842,9 @@
/*
* If the inode isn't dirty, then just release the inode flush lock and
- * do nothing. Treat stale inodes the same; we cannot rely on the
- * backing buffer remaining stale in cache for the remaining life of
- * the stale inode and so xfs_itobp() below may give us a buffer that
- * no longer contains inodes below. Doing this stale check here also
- * avoids forcing the log on pinned, stale inodes.
+ * do nothing.
*/
- if (xfs_inode_clean(ip) || xfs_iflags_test(ip, XFS_ISTALE)) {
+ if (xfs_inode_clean(ip)) {
xfs_ifunlock(ip);
return 0;
}
@@ -2872,6 +2868,19 @@
xfs_iunpin_wait(ip);
/*
+ * For stale inodes we cannot rely on the backing buffer remaining
+ * stale in cache for the remaining life of the stale inode and so
+ * xfs_itobp() below may give us a buffer that no longer contains
+ * inodes below. We have to check this after ensuring the inode is
+ * unpinned so that it is safe to reclaim the stale inode after the
+ * flush call.
+ */
+ if (xfs_iflags_test(ip, XFS_ISTALE)) {
+ xfs_ifunlock(ip);
+ return 0;
+ }
+
+ /*
* This may have been unpinned because the filesystem is shutting
* down forcibly. If that's the case we must not write this inode
* to disk, because the log record didn't make it to disk!