[Ocfs2-devel] + ocfs2-fix-use-after-free-when-unmounting-read-only-filesystem.patch added to mm-hotfixes-unstable branch

[Joseph Qi]

On 5/26/23 10:05 AM, Andrew Morton wrote:
> On Fri, 26 May 2023 09:36:25 +0800 Joseph Qi <joseph.qi at linux.alibaba.com> wrote:
> 
>> Hi Andrew,
>>
>> There is an updated version v2, which describe more clearly about the
>> case:
>> https://lore.kernel.org/ocfs2-devel/e9fc4b2f-1fcc-7c31-f346-59eccff50f9b@linux.alibaba.com/T/#u
> 
> Sigh.  Thanks.
> 
> As you can see from the above link, the email never hit ocfs2-devel and
> never hit my inbox.  I'll piece it together from your reply.
> 

Sorry for the inconvenience. I quote the updated description below:

"
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
"

> The ocfs2-devel list is really bad.  Can we move to a vger list?  Or
> get some maintenance work done on ocfs2-devel?
> 

I see. It seems something wrong with ocfs2-devel. But I'm not an
administrator of it:(

Thanks,
Joseph