linux-kernel - Re: [PATCH v2 1/2] ext4: fix bug_on in __es_tree_search caused by wrong s_usr_quota

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Date:   Mon, 24 Oct 2022 16:16:30 +0200
From:   Jan Kara <jack@...e.cz>
To:     Baokun Li <libaokun1@...wei.com>
Cc:     linux-ext4@...r.kernel.org, tytso@....edu,
        adilger.kernel@...ger.ca, jack@...e.cz, ritesh.list@...il.com,
        linux-kernel@...r.kernel.org, yi.zhang@...wei.com,
        yukuai3@...wei.com
Subject: Re: [PATCH v2 1/2] ext4: fix bug_on in __es_tree_search caused by
 wrong s_usr_quota_inum

On Mon 24-10-22 16:10:53, Jan Kara wrote:
> On Fri 21-10-22 12:07:30, Baokun Li wrote:
> > We got a issue as fllows:
> > ==================================================================
> >  kernel BUG at fs/ext4/extents_status.c:202!
> >  invalid opcode: 0000 [#1] PREEMPT SMP
> >  CPU: 1 PID: 810 Comm: mount Not tainted 6.1.0-rc1-next-g9631525255e3 #352
> >  RIP: 0010:__es_tree_search.isra.0+0xb8/0xe0
> >  RSP: 0018:ffffc90001227900 EFLAGS: 00010202
> >  RAX: 0000000000000000 RBX: 0000000077512a0f RCX: 0000000000000000
> >  RDX: 0000000000000002 RSI: 0000000000002a10 RDI: ffff8881004cd0c8
> >  RBP: ffff888177512ac8 R08: 47ffffffffffffff R09: 0000000000000001
> >  R10: 0000000000000001 R11: 00000000000679af R12: 0000000000002a10
> >  R13: ffff888177512d88 R14: 0000000077512a10 R15: 0000000000000000
> >  FS: 00007f4bd76dbc40(0000)GS:ffff88842fd00000(0000)knlGS:0000000000000000
> >  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >  CR2: 00005653bf993cf8 CR3: 000000017bfdf000 CR4: 00000000000006e0
> >  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> >  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >  Call Trace:
> >   <TASK>
> >   ext4_es_cache_extent+0xe2/0x210
> >   ext4_cache_extents+0xd2/0x110
> >   ext4_find_extent+0x5d5/0x8c0
> >   ext4_ext_map_blocks+0x9c/0x1d30
> >   ext4_map_blocks+0x431/0xa50
> >   ext4_getblk+0x82/0x340
> >   ext4_bread+0x14/0x110
> >   ext4_quota_read+0xf0/0x180
> >   v2_read_header+0x24/0x90
> >   v2_check_quota_file+0x2f/0xa0
> >   dquot_load_quota_sb+0x26c/0x760
> >   dquot_load_quota_inode+0xa5/0x190
> >   ext4_enable_quotas+0x14c/0x300
> >   __ext4_fill_super+0x31cc/0x32c0
> >   ext4_fill_super+0x115/0x2d0
> >   get_tree_bdev+0x1d2/0x360
> >   ext4_get_tree+0x19/0x30
> >   vfs_get_tree+0x26/0xe0
> >   path_mount+0x81d/0xfc0
> >   do_mount+0x8d/0xc0
> >   __x64_sys_mount+0xc0/0x160
> >   do_syscall_64+0x35/0x80
> >   entry_SYSCALL_64_after_hwframe+0x63/0xcd
> >   </TASK>
> > ==================================================================
> > 
> > Above issue may happen as follows:
> > -------------------------------------
> > ext4_fill_super
> >  ext4_orphan_cleanup
> >   ext4_enable_quotas
> >    ext4_quota_enable
> >     ext4_iget --> get error inode <5>
> >      ext4_ext_check_inode --> Wrong imode makes it escape inspection
> >      make_bad_inode(inode) --> EXT4_BOOT_LOADER_INO set imode
> >     dquot_load_quota_inode
> >      vfs_setup_quota_inode --> check pass
> >      dquot_load_quota_sb
> >       v2_check_quota_file
> >        v2_read_header
> >         ext4_quota_read
> >          ext4_bread
> >           ext4_getblk
> >            ext4_map_blocks
> >             ext4_ext_map_blocks
> >              ext4_find_extent
> >               ext4_cache_extents
> >                ext4_es_cache_extent
> >                 __es_tree_search.isra.0
> >                  ext4_es_end --> Wrong extents trigger BUG_ON
> > 
> > In the above issue, s_usr_quota_inum is set to 5, but inode<5> contains
> > incorrect imode and disordered extents. Because 5 is EXT4_BOOT_LOADER_INO,
> > the ext4_ext_check_inode check in the ext4_iget function can be bypassed,
> > finally, the extents that are not checked trigger the BUG_ON in the
> > __es_tree_search function. To solve this issue, check whether qf_inode
> > obtained by ext4_iget is bad_inode.
> > 
> > Signed-off-by: Baokun Li <libaokun1@...wei.com>
> 
> Looks good to me. Feel free to add:
> 
> Reviewed-by: Jan Kara <jack@...e.cz>

Hum, on a second thought: Would not it be better if vfs_setup_quota_inode()
actually checked for bad inode and refused it with EUCLEAN? That would
sound like a more generic approach (covers all filesystems) to this
problem.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR