Re: [PATCH] fs: improve dump_mapping() robustness

Baolin Wang
2024-01-18T01:27:19Z

On 1/16/2024 7:16 PM, Christian Brauner wrote:
> On Tue, 16 Jan 2024 15:53:35 +0800, Baolin Wang wrote:
>> We met a kernel crash issue when running stress-ng testing, and the
>> system crashes when printing the dentry name in dump_mapping().
>>
>> Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
>> pc : dentry_name+0xd8/0x224
>> lr : pointer+0x22c/0x370
>> sp : ffff800025f134c0
>> ......
>> Call trace:
>> dentry_name+0xd8/0x224
>> pointer+0x22c/0x370
>> vsnprintf+0x1ec/0x730
>> vscnprintf+0x2c/0x60
>> vprintk_store+0x70/0x234
>> vprintk_emit+0xe0/0x24c
>> vprintk_default+0x3c/0x44
>> vprintk_func+0x84/0x2d0
>> printk+0x64/0x88
>> __dump_page+0x52c/0x530
>> dump_page+0x14/0x20
>> set_migratetype_isolate+0x110/0x224
>> start_isolate_page_range+0xc4/0x20c
>> offline_pages+0x124/0x474
>> memory_block_offline+0x44/0xf4
>> memory_subsys_offline+0x3c/0x70
>> device_offline+0xf0/0x120
>> ......
>>
>> [...]
>
> Seems fine for debugging purposes. Let me know if this needs to go through
> somewhere else.

Going through VFS tree is fine to me. Thanks.