ocfs2: fix use-after-free when unmounting read-only filesystem

It's trivial to trigger a use-after-free bug in the ocfs2 quotas code using
fstest generic/452.  After a read-only remount, quotas are suspended and
ocfs2_mem_dqinfo is freed through ->ocfs2_local_free_info().  When unmounting
the filesystem, an UAF access to the oinfo will eventually cause a crash.

BUG: KASAN: slab-use-after-free in timer_delete+0x54/0xc0
Read of size 8 at addr ffff8880389a8208 by task umount/669
...
Call Trace:
 <TASK>
 ...
 timer_delete+0x54/0xc0
 try_to_grab_pending+0x31/0x230
 __cancel_work_timer+0x6c/0x270
 ocfs2_disable_quotas.isra.0+0x3e/0xf0 [ocfs2]
 ocfs2_dismount_volume+0xdd/0x450 [ocfs2]
 generic_shutdown_super+0xaa/0x280
 kill_block_super+0x46/0x70
 deactivate_locked_super+0x4d/0xb0
 cleanup_mnt+0x135/0x1f0
 ...
 </TASK>

Allocated by task 632:
 kasan_save_stack+0x1c/0x40
 kasan_set_track+0x21/0x30
 __kasan_kmalloc+0x8b/0x90
 ocfs2_local_read_info+0xe3/0x9a0 [ocfs2]
 dquot_load_quota_sb+0x34b/0x680
 dquot_load_quota_inode+0xfe/0x1a0
 ocfs2_enable_quotas+0x190/0x2f0 [ocfs2]
 ocfs2_fill_super+0x14ef/0x2120 [ocfs2]
 mount_bdev+0x1be/0x200
 legacy_get_tree+0x6c/0xb0
 vfs_get_tree+0x3e/0x110
 path_mount+0xa90/0xe10
 __x64_sys_mount+0x16f/0x1a0
 do_syscall_64+0x43/0x90
 entry_SYSCALL_64_after_hwframe+0x72/0xdc

Freed by task 650:
 kasan_save_stack+0x1c/0x40
 kasan_set_track+0x21/0x30
 kasan_save_free_info+0x2a/0x50
 __kasan_slab_free+0xf9/0x150
 __kmem_cache_free+0x89/0x180
 ocfs2_local_free_info+0x2ba/0x3f0 [ocfs2]
 dquot_disable+0x35f/0xa70
 ocfs2_susp_quotas.isra.0+0x159/0x1a0 [ocfs2]
 ocfs2_remount+0x150/0x580 [ocfs2]
 reconfigure_super+0x1a5/0x3a0
 path_mount+0xc8a/0xe10
 __x64_sys_mount+0x16f/0x1a0
 do_syscall_64+0x43/0x90
 entry_SYSCALL_64_after_hwframe+0x72/0xdc

Link: https://lkml.kernel.org/r/20230522102112.9031-1-lhenriques@suse.de
Signed-off-by: Luís Henriques <lhenriques@suse.de>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Tested-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Gang He <ghe@suse.com>
Cc: Jun Piao <piaojun@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index 0b0e6a1..988d1c0 100644 (file)
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -952,8 +952,10 @@ static void ocfs2_disable_quotas(struct ocfs2_super *osb)
        for (type = 0; type < OCFS2_MAXQUOTAS; type++) {
                if (!sb_has_quota_loaded(sb, type))
                        continue;
-               oinfo = sb_dqinfo(sb, type)->dqi_priv;
-               cancel_delayed_work_sync(&oinfo->dqi_sync_work);
+               if (!sb_has_quota_suspended(sb, type)) {
+                       oinfo = sb_dqinfo(sb, type)->dqi_priv;
+                       cancel_delayed_work_sync(&oinfo->dqi_sync_work);
+               }
                inode = igrab(sb->s_dquot.files[type]);
                /* Turn off quotas. This will remove all dquot structures from
                 * memory and so they will be automatically synced to global