Re: [PATCH v3 1/4] ext4: fix bug_on in __es_tree_search caused by bad quota inode

[Chaitanya Kulkarni]

On 10/25/2022 9:23 PM, 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 the inode is
> bad_inode in vfs_setup_quota_inode().
> 
> Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>


The analysis and the provided call chain looks really good, only thing 
non-blocker is missing that maintainer might want it version history.

Reviewed-by: Chaitanya Kulkarni <kch@xxxxxxxxxx>

-ck