Received-SPF: pass (google.com: domain of linux-kernel+bounces-29621-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1;
Message-ID: <07ccff45-a728-4ed1-86f4-91517c656609@linux.alibaba.com>
Date: Thu, 18 Jan 2024 09:27:41 +0800
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH] fs: improve dump_mapping() robustness
To: Christian Brauner <brauner@kernel.org>
Cc: willy@infradead.org, viro@zeniv.linux.org.uk, jack@suse.cz,
 linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
 linux-kernel@vger.kernel.org, akpm@linux-foundation.org
References: <937ab1f87328516821d39be672b6bc18861d9d3e.1705391420.git.baolin.wang@linux.alibaba.com>
 <20240116-privat-zeitplan-21db23926f45@brauner>
From: Baolin Wang <baolin.wang@linux.alibaba.com>
In-Reply-To: <20240116-privat-zeitplan-21db23926f45@brauner>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit


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.