From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-130.freemail.mail.aliyun.com (out30-130.freemail.mail.aliyun.com [115.124.30.130]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7AA6B3D86; Thu, 18 Jan 2024 01:27:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.130 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705541243; cv=none; b=LwllQuoLShR7o7DWFAxzw6ZShtEvn0ZPlQaYJsmgHTEsYHehq3rbcPTpIBCWo1IE8u8YxN3r0UXdOssVBFjrywC+TSlyNX+osMeKhnIaFUMw3Ju3uhT8xljQXoyf00156ulnCYB0JbywSgVhKAFheruN4aajo5lnOaYZq7onw1o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705541243; c=relaxed/simple; bh=WHyD5iPCBkA+qBJQvCftbeGK8fR2RfKEGijwDbE/Mks=; h=X-Alimail-AntiSpam:Received:Message-ID:Date:MIME-Version: User-Agent:Subject:To:Cc:References:From:In-Reply-To:Content-Type: Content-Transfer-Encoding; b=SvtyBtZxmUzUaXBgWLEQ1y1LLxjH6v89EZPOLlpKBTL6la1dtzeeomg4gwfZKcr3jHTENkBQxPR+uDrFK3jKa+WvEX62fC+Xymmfq+N8JqlwcPZAd9/QCDC+qR7uvbPYSnSKKHZIwIvdeWrkY6YbFZtbtZuk4cDAOMmNotNQgf8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; arc=none smtp.client-ip=115.124.30.130 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R591e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046050;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---0W-qs3Uk_1705541230; Received: from 30.97.48.47(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0W-qs3Uk_1705541230) by smtp.aliyun-inc.com; Thu, 18 Jan 2024 09:27:10 +0800 Message-ID: <07ccff45-a728-4ed1-86f4-91517c656609@linux.alibaba.com> Date: Thu, 18 Jan 2024 09:27:41 +0800 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] fs: improve dump_mapping() robustness To: Christian Brauner 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 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.