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authorDave Chinner <dchinner@redhat.com>2018-05-10 21:50:23 -0700
committerDarrick J. Wong <darrick.wong@oracle.com>2018-05-15 17:57:05 -0700
commitc9fbd7bbc23dbdd73364be4d045e5d3612cf6e82 (patch)
tree044ffcd49ff39cdbdbb900b8cb47a5286b9fb3f1
parentdae5cd811852c92072f89b36242981e05f856d5b (diff)
xfs: clear sb->s_fs_info on mount failure
We recently had an oops reported on a 4.14 kernel in xfs_reclaim_inodes_count() where sb->s_fs_info pointed to garbage and so the m_perag_tree lookup walked into lala land. Essentially, the machine was under memory pressure when the mount was being run, xfs_fs_fill_super() failed after allocating the xfs_mount and attaching it to sb->s_fs_info. It then cleaned up and freed the xfs_mount, but the sb->s_fs_info field still pointed to the freed memory. Hence when the superblock shrinker then ran it fell off the bad pointer. With the superblock shrinker problem fixed at teh VFS level, this stale s_fs_info pointer is still a problem - we use it unconditionally in ->put_super when the superblock is being torn down, and hence we can still trip over it after a ->fill_super call failure. Hence we need to clear s_fs_info if xfs-fs_fill_super() fails, and we need to check if it's valid in the places it can potentially be dereferenced after a ->fill_super failure. Signed-Off-By: Dave Chinner <dchinner@redhat.com> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
-rw-r--r--fs/xfs/xfs_super.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index f19fe291356e..39e5ec3d407f 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1772,6 +1772,7 @@ xfs_fs_fill_super(
out_close_devices:
xfs_close_devices(mp);
out_free_fsname:
+ sb->s_fs_info = NULL;
xfs_free_fsname(mp);
kfree(mp);
out:
@@ -1789,6 +1790,10 @@ xfs_fs_put_super(
{
struct xfs_mount *mp = XFS_M(sb);
+ /* if ->fill_super failed, we have no mount to tear down */
+ if (!sb->s_fs_info)
+ return;
+
xfs_notice(mp, "Unmounting Filesystem");
xfs_filestream_unmount(mp);
xfs_unmountfs(mp);
@@ -1798,6 +1803,8 @@ xfs_fs_put_super(
xfs_destroy_percpu_counters(mp);
xfs_destroy_mount_workqueues(mp);
xfs_close_devices(mp);
+
+ sb->s_fs_info = NULL;
xfs_free_fsname(mp);
kfree(mp);
}
@@ -1817,6 +1824,9 @@ xfs_fs_nr_cached_objects(
struct super_block *sb,
struct shrink_control *sc)
{
+ /* Paranoia: catch incorrect calls during mount setup or teardown */
+ if (WARN_ON_ONCE(!sb->s_fs_info))
+ return 0;
return xfs_reclaim_inodes_count(XFS_M(sb));
}