________________________________________
发件人: Johannes Thumshirn <johannes.thumsh...@wdc.com>
发送时间: 2020年9月21日 17:17
收件人: Zhang, Qiang; c...@fb.com; jo...@toxicpanda.com; dste...@suse.com;
syzbot+582e66e5edf36a22c...@syzkaller.appspotmail.com
抄送: linux-bt...@vger.kernel.org; linux-kernel@vger.kernel.org
主题: Re: 回复: [PATCH] btrfs: Fix missing close devices
On 21/09/2020 11:14, Zhang, Qiang wrote:
>
>
> ________________________________________
> 发件人: Johannes Thumshirn <johannes.thumsh...@wdc.com>
> 发送时间: 2020年9月21日 16:52
> 收件人: Zhang, Qiang; c...@fb.com; jo...@toxicpanda.com; dste...@suse.com
> 抄送: linux-bt...@vger.kernel.org; linux-kernel@vger.kernel.org
> 主题: Re: [PATCH] btrfs: Fix missing close devices
>
> On 21/09/2020 10:27, qiang.zh...@windriver.com wrote:
>> From: Zqiang <qiang.zh...@windriver.com>
>>
>> When the btrfs fill super error, we should first close devices and
>> then call deactivate_locked_super func to free fs_info.
>>
>> Signed-off-by: Zqiang <qiang.zh...@windriver.com>
>> ---
>> fs/btrfs/super.c | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
>> index 8840a4fa81eb..3bfd54e8f388 100644
>> --- a/fs/btrfs/super.c
>> +++ b/fs/btrfs/super.c
>> @@ -1675,6 +1675,7 @@ static struct dentry *btrfs_mount_root(struct
>> file_system_type *fs_type,
>> error = security_sb_set_mnt_opts(s, new_sec_opts, 0, NULL);
>> security_free_mnt_opts(&new_sec_opts);
>> if (error) {
>> + btrfs_close_devices(fs_devices);
>> deactivate_locked_super(s);
>> return ERR_PTR(error);
>> }
>>
>
>> I think this is the fix for the syzkaller issue:
>> Reported-by: syzbot+582e66e5edf36a22c...@syzkaller.appspotmail.com
>
> Please try this patch.
>
>Nope, with this patch I get the following Null-ptr-deref:
>[ 39.065209]
>>==================================================================
>[ 39.066318] BUG: KASAN: null-ptr-deref in bdev_name.constprop.0+0xd4/0x240
>[ 39.067307] Read of size 4 at addr 00000000000003ac by task syz-repro/273
>[ 39.068289]
>[ 39.069602]
>>==================================================================
>[ 39.070837] BUG: kernel NULL pointer dereference, address: 00000000000003ac
>[ 39.071837] #PF: supervisor read access in kernel mode
>[ 39.072580] #PF: error_code(0x0000) - not-present page
>[ 39.073318] PGD 80000001cd3b1067 P4D 80000001cd3b1067 PUD 1c6de7067 PMD >0
>[ 39.074306] Oops: 0000 [#1] SMP KASAN PTI
>[ 39.074887] CPU: 0 PID: 273 Comm: syz-repro Tainted: G B
>5.9.0-rc5+ >#772
>[ 39.076031] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
>>rel-1.13.0-0-gf21b5a4-rebuilt.opensuse.org 04/01/2014
>[ 39.077638] RIP: 0010:bdev_name.constprop.0+0xd4/0x240
>[ 39.078387] Code: ca 4c 89 4c 24 08 e8 0b e9 ff ff 48 89 df 49 89 c6 e8 40
>42 c6 ff 49 >8b ac 24 e0 00 00 00 48 8d bd ac 03 00 00 e8 2c 41 c6 ff <8b> 85
>ac 03 00 00 4c 8b 4c >24 08 85 c0 0f 84 fe 00 00 00 4c 89 cf
>[ 39.080991] RSP: 0018:ffff8881f1a97878 EFLAGS: 00010286
>[ 39.081728] RAX: 0000000000000001 RBX: ffff8881c9fb80e0 RCX:
>>dffffc0000000000
>[ 39.082725] RDX: 0000000000000007 RSI: 0000000000000004 RDI:
>ffffffff81acd784
>[ 39.083717] RBP: 0000000000000000 R08: 0000000000000000 R09:
>>>0000000000000000
>[ 39.084722] R10: fffffbfff0539591 R11: 0000000000000001 R12:
>ffff8881c9fb8000
>[ 39.085711] R13: ffff8881ef6e2698 R14: ffff8881ef6e2680 R15:
>0000000000000000
>[ 39.086704] FS: 00007f5d36eb9540(0000) GS:ffff8881f7600000(0000)
>>knlGS:0000000000000000
>[ 39.087827] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>[ 39.088623] CR2: 00000000000003ac CR3: 00000001ef552000 CR4:
>00000000000006b0
>[ 39.089607] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
>0000000000000000
>[ 39.090603] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
>0000000000000400
>[ 39.091583] Call Trace:
>[ 39.091943] ? mac_address_string+0x380/0x380
>[ 39.092559] ? mark_held_locks+0x65/0x90
>[ 39.093116] pointer+0x21c/0x650
>[ 39.093578] ? format_decode+0x1cf/0x4e0
>[ 39.094139] ? resource_string.isra.0+0xc10/0xc10
>[ 39.094809] vsnprintf+0x2e0/0x820
>[ 39.095292] ? pointer+0x650/0x650
>[ 39.095785] snprintf+0x88/0xa0
>[ 39.096234] ? vsprintf+0x10/0x10
>[ 39.096708] ? rcu_read_lock_sched_held+0x3a/0x70
>[ 39.097378] ? sget+0x200/0x240
>[ 39.097908] ? btrfs_kill_super+0x30/0x30 [btrfs]
>[ 39.098644] btrfs_mount_root+0x442/0x5d0 [btrfs]
>[ 39.099377] ? parse_rescue_options+0x150/0x150 [btrfs]
>[ 39.100103] ? rcu_read_lock_sched_held+0x3a/0x70
>[ 39.100759] ? vfs_parse_fs_string+0xbc/0xf0
>[ 39.101355] ? kfree+0x1e0/0x310
>[ 39.101816] ? vfs_parse_fs_string+0xbc/0xf0
>[ 39.102493] ? parse_rescue_options+0x150/0x150 [btrfs]
>[ 39.103219] legacy_get_tree+0x7d/0xc0
>[ 39.103750] vfs_get_tree+0x48/0x100
>[ 39.104263] ? parse_monolithic_mount_data+0x1c/0x40
>[ 39.104960] vfs_kern_mount.part.0+0x70/0xd0
>[ 39.105649] btrfs_mount+0x187/0x550 [btrfs]
>[ 39.106268] ? mark_held_locks+0x24/0x90
>[ 39.106918] ? btrfs_show_options+0x730/0x730 [btrfs]
>[ 39.107641] ? lockdep_hardirqs_on_prepare+0x146/0x240
>[ 39.108368] ? strcmp+0x2e/0x50
>[ 39.108810] ? rcu_read_lock_sched_held+0x3a/0x70
>[ 39.109461] ? vfs_parse_fs_string+0xbc/0xf0
>[ 39.110054] ? kfree+0x1e0/0x310
>[ 39.110519] ? vfs_parse_fs_string+0xbc/0xf0
>[ 39.111197] ? btrfs_show_options+0x730/0x730 [btrfs]
>[ 39.111898] legacy_get_tree+0x7d/0xc0
>[ 39.112427] vfs_get_tree+0x48/0x100
>[ 39.112928] path_mount+0xa37/0xfc0
>[ 39.113422] ? strncpy_from_user+0xde/0x1f0
>[ 39.114011] ? copy_mount_string+0x20/0x20
>[ 39.114588] ? getname_flags+0xa7/0x220
>[ 39.115132] ? _copy_from_user+0x8e/0xd0
>[ 39.115686] __x64_sys_mount+0x16b/0x1a0
>[ 39.116242] ? copy_mnt_ns+0x540/0x540
>[ 39.116770] ? trace_hardirqs_on+0x34/0x130
>[ 39.117370] do_syscall_64+0x33/0x40
>[ 39.117886] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>[ 39.118604] RIP: 0033:0x7f5d36df1eda
Hello Johannes Thumshirn
the crash happend in "snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev)" in
btrfs_mount_root func, the "bdev" may be destroyed in btrfs_close_devices.
I think add btrfs_close_devices func before deactivate_locked_super is
reasonable.
I'm not sure if that's another problem .
What's your point of view ？
