linux-kernel - Re: [PATCH] fs: improve dump

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Message-ID: <07ccff45-a728-4ed1-86f4-91517c656609@linux.alibaba.com>
Date: Thu, 18 Jan 2024 09:27:41 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: Christian Brauner <brauner@...nel.org>
Cc: willy@...radead.org, viro@...iv.linux.org.uk, jack@...e.cz,
 linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
 linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: Re: [PATCH] fs: improve dump_mapping() robustness



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.