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authorDave Chinner <dchinner@redhat.com>2018-05-10 21:50:23 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-10-17 13:41:06 -0700
commit748edae843c30f41fdcb320f1a8335bc2238b961 (patch)
treea450611203adb2d0b94356ce101de420cc9af8f3
parentf9c94a02d4c5abccecb893a42247dfe24da8bdad (diff)
xfs: clear sb->s_fs_info on mount failure
commit c9fbd7bbc23dbdd73364be4d045e5d3612cf6e82 upstream. 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> Signed-off-by: Ajay Kaher <akaher@vmware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-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 ef64a1e1a66a..ff3f5812c0fd 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1572,6 +1572,7 @@ 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:
@@ -1589,6 +1590,10 @@ 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);
@@ -1598,6 +1603,8 @@ 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);
}
@@ -1617,6 +1624,9 @@ 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));
}