From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f198.google.com (mail-wr0-f198.google.com [209.85.128.198]) by kanga.kvack.org (Postfix) with ESMTP id 7A23E6B0007 for ; Thu, 1 Feb 2018 23:50:31 -0500 (EST) Received: by mail-wr0-f198.google.com with SMTP id w10so2662771wrg.2 for ; Thu, 01 Feb 2018 20:50:31 -0800 (PST) Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk. [195.92.253.2]) by mx.google.com with ESMTPS id q61si995608wrb.483.2018.02.01.20.50.30 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 01 Feb 2018 20:50:30 -0800 (PST) Date: Fri, 2 Feb 2018 04:50:20 +0000 From: Al Viro Subject: Re: possible deadlock in get_user_pages_unlocked Message-ID: <20180202045020.GF30522@ZenIV.linux.org.uk> References: <001a113f6344393d89056430347d@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <001a113f6344393d89056430347d@google.com> Sender: owner-linux-mm@kvack.org List-ID: To: syzbot Cc: akpm@linux-foundation.org, aneesh.kumar@linux.vnet.ibm.com, dan.j.williams@intel.com, james.morse@arm.com, kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mingo@kernel.org, syzkaller-bugs@googlegroups.com On Thu, Feb 01, 2018 at 04:58:00PM -0800, syzbot wrote: > Hello, > > syzbot hit the following crash on upstream commit > 7109a04eae81c41ed529da9f3c48c3655ccea741 (Thu Feb 1 17:37:30 2018 +0000) > Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/ide > > So far this crash happened 2 times on upstream. > C reproducer is attached. Umm... How reproducible that is? > syzkaller reproducer is attached. > Raw console output is attached. > compiler: gcc (GCC) 7.1.1 20170620 > .config is attached. Can't reproduce with gcc 5.4.1 (same .config, same C reproducer). It looks like __get_user_pages_locked() returning with *locked zeroed, but ->mmap_sem not dropped. I don't see what could've lead to it and attempts to reproduce had not succeeded so far... How long does it normally take for lockdep splat to trigger? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org