From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it1-f199.google.com (mail-it1-f199.google.com [209.85.166.199]) by kanga.kvack.org (Postfix) with ESMTP id ABBD28E00D7 for ; Fri, 25 Jan 2019 11:02:28 -0500 (EST) Received: by mail-it1-f199.google.com with SMTP id k133so5991985ite.4 for ; Fri, 25 Jan 2019 08:02:28 -0800 (PST) Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [202.181.97.72]) by mx.google.com with ESMTPS id 8si5800709jak.74.2019.01.25.08.02.26 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 25 Jan 2019 08:02:27 -0800 (PST) Subject: Re: possible deadlock in __do_page_fault References: <201901230201.x0N214eq043832@www262.sakura.ne.jp> <20190123155751.GA168927@google.com> <201901240152.x0O1qUUU069046@www262.sakura.ne.jp> <20190124134646.GA53008@google.com> From: Tetsuo Handa Message-ID: Date: Sat, 26 Jan 2019 01:02:06 +0900 MIME-Version: 1.0 In-Reply-To: <20190124134646.GA53008@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Joel Fernandes Cc: Andrew Morton , Todd Kjos , syzbot+a76129f18c89f3e2ddd4@syzkaller.appspotmail.com, ak@linux.intel.com, Johannes Weiner , jack@suse.cz, jrdr.linux@gmail.com, LKML , linux-mm@kvack.org, mawilcox@microsoft.com, mgorman@techsingularity.net, syzkaller-bugs@googlegroups.com, =?UTF-8?Q?Arve_Hj=c3=b8nnev=c3=a5g?= , Todd Kjos , Martijn Coenen , Greg Kroah-Hartman On 2019/01/24 22:46, Joel Fernandes wrote: > On Thu, Jan 24, 2019 at 10:52:30AM +0900, Tetsuo Handa wrote: >> Joel Fernandes wrote: >>>> Anyway, I need your checks regarding whether this approach is waiting for >>>> completion at all locations which need to wait for completion. >>> >>> I think you are waiting in unwanted locations. The only location you need to >>> wait in is ashmem_pin_unpin. >>> >>> So, to my eyes all that is needed to fix this bug is: >>> >>> 1. Delete the range from the ashmem_lru_list >>> 2. Release the ashmem_mutex >>> 3. fallocate the range. >>> 4. Do the completion so that any waiting pin/unpin can proceed. >>> >>> Could you clarify why you feel you need to wait for completion at those other >>> locations? OK. Here is an updated patch. Passed syzbot's best-effort testing using reproducers on all three reports. >>From f192176dbee54075d41249e9f22918c32cb4d4fc Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Fri, 25 Jan 2019 23:43:01 +0900 Subject: [PATCH] staging: android: ashmem: Don't call fallocate() with ashmem_mutex held. syzbot is hitting lockdep warnings [1][2][3]. This patch tries to fix the warning by eliminating ashmem_shrink_scan() => {shmem|vfs}_fallocate() sequence. [1] https://syzkaller.appspot.com/bug?id=87c399f6fa6955006080b24142e2ce7680295ad4 [2] https://syzkaller.appspot.com/bug?id=7ebea492de7521048355fc84210220e1038a7908 [3] https://syzkaller.appspot.com/bug?id=e02419c12131c24e2a957ea050c2ab6dcbbc3270 Reported-by: syzbot Reported-by: syzbot Reported-by: syzbot Signed-off-by: Tetsuo Handa --- drivers/staging/android/ashmem.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c index 90a8a9f..d40c1d2 100644 --- a/drivers/staging/android/ashmem.c +++ b/drivers/staging/android/ashmem.c @@ -75,6 +75,9 @@ struct ashmem_range { /* LRU list of unpinned pages, protected by ashmem_mutex */ static LIST_HEAD(ashmem_lru_list); +static atomic_t ashmem_shrink_inflight = ATOMIC_INIT(0); +static DECLARE_WAIT_QUEUE_HEAD(ashmem_shrink_wait); + /* * long lru_count - The count of pages on our LRU list. * @@ -438,7 +441,6 @@ static int ashmem_mmap(struct file *file, struct vm_area_struct *vma) static unsigned long ashmem_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) { - struct ashmem_range *range, *next; unsigned long freed = 0; /* We might recurse into filesystem code, so bail out if necessary */ @@ -448,17 +450,27 @@ static int ashmem_mmap(struct file *file, struct vm_area_struct *vma) if (!mutex_trylock(&ashmem_mutex)) return -1; - list_for_each_entry_safe(range, next, &ashmem_lru_list, lru) { + while (!list_empty(&ashmem_lru_list)) { + struct ashmem_range *range = + list_first_entry(&ashmem_lru_list, typeof(*range), lru); loff_t start = range->pgstart * PAGE_SIZE; loff_t end = (range->pgend + 1) * PAGE_SIZE; + struct file *f = range->asma->file; - range->asma->file->f_op->fallocate(range->asma->file, - FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, - start, end - start); + get_file(f); + atomic_inc(&ashmem_shrink_inflight); range->purged = ASHMEM_WAS_PURGED; lru_del(range); freed += range_size(range); + mutex_unlock(&ashmem_mutex); + f->f_op->fallocate(f, + FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, + start, end - start); + fput(f); + if (atomic_dec_and_test(&ashmem_shrink_inflight)) + wake_up_all(&ashmem_shrink_wait); + mutex_lock(&ashmem_mutex); if (--sc->nr_to_scan <= 0) break; } @@ -713,6 +725,7 @@ static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd, return -EFAULT; mutex_lock(&ashmem_mutex); + wait_event(ashmem_shrink_wait, !atomic_read(&ashmem_shrink_inflight)); if (!asma->file) goto out_unlock; -- 1.8.3.1 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F3422C282C0 for ; Fri, 25 Jan 2019 16:02:29 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9F00B218D0 for ; Fri, 25 Jan 2019 16:02:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9F00B218D0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=i-love.sakura.ne.jp Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id EC7E28E00D8; Fri, 25 Jan 2019 11:02:28 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E75A78E00D7; Fri, 25 Jan 2019 11:02:28 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D674A8E00D8; Fri, 25 Jan 2019 11:02:28 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from mail-it1-f199.google.com (mail-it1-f199.google.com [209.85.166.199]) by kanga.kvack.org (Postfix) with ESMTP id ABBD28E00D7 for ; Fri, 25 Jan 2019 11:02:28 -0500 (EST) Received: by mail-it1-f199.google.com with SMTP id k133so5991985ite.4 for ; Fri, 25 Jan 2019 08:02:28 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:subject:to:cc :references:from:message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=CqCtzfmNIlsjjr37EaboZ+t7nVgdj0ZPM+y425F5GJQ=; b=t34WhCgTPb/ifFtnI01HsTRDVQ5YEuJ3zRd28JOA1rjpAvb6BHZtb3hZ1C+p89DRoR 0ouUPMHI93TdJN4IRjDZWjpXqkhCsrGh23UW5t1mSGTu6/0iP9jJEIoQrfxDz8OQ+xcj nAS9bx4g1PDDkiatdvoPaEFoFvLDX4XvMMOCPdv2iKp4LrEmvI1gVkqsZRObk+uCq1qO fw81j39N7lrWcX4ayJgWuDhxerWU80l4b4RPl19hg6jXynWGe++At3UG/89aRYtOMnb2 Rx7TVFoW9omMta302O31OMKQgRrlBPP/2Bq+HFVhgOoHBunzkaclv3whXhmH0OfSHYlQ o2vA== X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of penguin-kernel@i-love.sakura.ne.jp designates 202.181.97.72 as permitted sender) smtp.mailfrom=penguin-kernel@i-love.sakura.ne.jp X-Gm-Message-State: AJcUukesW8nUkOhP0wtqKUpQsVS6Il8gAwxviNaHuNtYWash9k0rjdI5 ZENDhTMmtfxeRQMW+eZP2opjwQA2qZ314hhohlU2xFXngs1A0CmISyW+i+7xThcT8kUB/flN0d8 9NSYrsopOSqevVRsnUnFOh5RcIsMuBB4C6nlM1ht/xoPJhrvxo43ArGpPU7rDqmMwpQ== X-Received: by 2002:a02:a791:: with SMTP id e17mr7930925jaj.104.1548432148356; Fri, 25 Jan 2019 08:02:28 -0800 (PST) X-Google-Smtp-Source: ALg8bN7xJ1YhEIg1hJWn1WPdAnlEeJnqtU2dBRQWFGdKqbDbWFXW4lKJ4CZdbN2wTND7imr9yibz X-Received: by 2002:a02:a791:: with SMTP id e17mr7930872jaj.104.1548432147389; Fri, 25 Jan 2019 08:02:27 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1548432147; cv=none; d=google.com; s=arc-20160816; b=QCKKj8CSUZyfbYyyw9nnGRB622ojG+XkhyVZ8UakGpUjPjNz8zhtPcDh8r5wxQKTva t4m1dWMq1vGvIP2y9y4M4RVVxraP/FOcqnIXQ9D4zUJTYgwAaaRy+H01Z+w2x1VZGw3W JnodtjWFGnR93pe3PIr2g4rVcoZ5iqi5SqxXuARFIzP9X6JvzdsDuuskjjJT1S3yLzZV HsSdmlphMKkP4S7PxUncnWclW8G9HzzjIE17mMjK+ezceDztsKhLugqB63roG33Cz1Dh 0BiDEBXeGXetz6UjLVY4OJnTnztpaZ8vY7EaSOivkR4T8hZLrxmQ3UnjWLd7tL+YDRVC EasA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:content-language:in-reply-to:mime-version :user-agent:date:message-id:from:references:cc:to:subject; bh=CqCtzfmNIlsjjr37EaboZ+t7nVgdj0ZPM+y425F5GJQ=; b=TtO3zVqQJBJ2mD9iK+z1gcc0/ZLatKQs6a/23zLHQW2TMpziQ+0CQ3NSJOw5/fQ8NZ NcEUJJ1ZPWkhbP25BfP/6M9fjeoNeVFdlIhHkwZ5LkYknqVCU26R1H08ocWAVPDu4FJ4 v/4WoMfZYC+YfU+/REk/OZED3w14krjbCrRMV3LcVfrOF+oW6STCeYG24f/nmbi6ySQ+ 3UqxZVugAPykr5n5MJNmJ5ozNSNAkKcsEkdm3+/3mbnE7iQnvkgX6EQ3gZbGeaUyxJKF hb6I+2cEAAq660okfO8q4uljgbeEkMpKiAFGAVgxyXJaTVRz97BAZmffAjGhOgSsoV+z OD4w== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of penguin-kernel@i-love.sakura.ne.jp designates 202.181.97.72 as permitted sender) smtp.mailfrom=penguin-kernel@i-love.sakura.ne.jp Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [202.181.97.72]) by mx.google.com with ESMTPS id 8si5800709jak.74.2019.01.25.08.02.26 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 25 Jan 2019 08:02:27 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of penguin-kernel@i-love.sakura.ne.jp designates 202.181.97.72 as permitted sender) client-ip=202.181.97.72; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of penguin-kernel@i-love.sakura.ne.jp designates 202.181.97.72 as permitted sender) smtp.mailfrom=penguin-kernel@i-love.sakura.ne.jp Received: from fsav107.sakura.ne.jp (fsav107.sakura.ne.jp [27.133.134.234]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id x0PG26fg055728; Sat, 26 Jan 2019 01:02:06 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav107.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav107.sakura.ne.jp); Sat, 26 Jan 2019 01:02:06 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav107.sakura.ne.jp) Received: from [192.168.1.8] (softbank126126163036.bbtec.net [126.126.163.36]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id x0PG26Rv055723 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NO); Sat, 26 Jan 2019 01:02:06 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: possible deadlock in __do_page_fault To: Joel Fernandes Cc: Andrew Morton , Todd Kjos , syzbot+a76129f18c89f3e2ddd4@syzkaller.appspotmail.com, ak@linux.intel.com, Johannes Weiner , jack@suse.cz, jrdr.linux@gmail.com, LKML , linux-mm@kvack.org, mawilcox@microsoft.com, mgorman@techsingularity.net, syzkaller-bugs@googlegroups.com, =?UTF-8?Q?Arve_Hj=c3=b8nnev=c3=a5g?= , Todd Kjos , Martijn Coenen , Greg Kroah-Hartman References: <201901230201.x0N214eq043832@www262.sakura.ne.jp> <20190123155751.GA168927@google.com> <201901240152.x0O1qUUU069046@www262.sakura.ne.jp> <20190124134646.GA53008@google.com> From: Tetsuo Handa Message-ID: Date: Sat, 26 Jan 2019 01:02:06 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190124134646.GA53008@google.com> Content-Type: text/plain; charset="UTF-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Message-ID: <20190125160206.Lfyx0PANeYIdIaPchF-v6h4CR00qVm2tFHf2jEck24s@z> On 2019/01/24 22:46, Joel Fernandes wrote: > On Thu, Jan 24, 2019 at 10:52:30AM +0900, Tetsuo Handa wrote: >> Joel Fernandes wrote: >>>> Anyway, I need your checks regarding whether this approach is waiting for >>>> completion at all locations which need to wait for completion. >>> >>> I think you are waiting in unwanted locations. The only location you need to >>> wait in is ashmem_pin_unpin. >>> >>> So, to my eyes all that is needed to fix this bug is: >>> >>> 1. Delete the range from the ashmem_lru_list >>> 2. Release the ashmem_mutex >>> 3. fallocate the range. >>> 4. Do the completion so that any waiting pin/unpin can proceed. >>> >>> Could you clarify why you feel you need to wait for completion at those other >>> locations? OK. Here is an updated patch. Passed syzbot's best-effort testing using reproducers on all three reports. >From f192176dbee54075d41249e9f22918c32cb4d4fc Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Fri, 25 Jan 2019 23:43:01 +0900 Subject: [PATCH] staging: android: ashmem: Don't call fallocate() with ashmem_mutex held. syzbot is hitting lockdep warnings [1][2][3]. This patch tries to fix the warning by eliminating ashmem_shrink_scan() => {shmem|vfs}_fallocate() sequence. [1] https://syzkaller.appspot.com/bug?id=87c399f6fa6955006080b24142e2ce7680295ad4 [2] https://syzkaller.appspot.com/bug?id=7ebea492de7521048355fc84210220e1038a7908 [3] https://syzkaller.appspot.com/bug?id=e02419c12131c24e2a957ea050c2ab6dcbbc3270 Reported-by: syzbot Reported-by: syzbot Reported-by: syzbot Signed-off-by: Tetsuo Handa --- drivers/staging/android/ashmem.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c index 90a8a9f..d40c1d2 100644 --- a/drivers/staging/android/ashmem.c +++ b/drivers/staging/android/ashmem.c @@ -75,6 +75,9 @@ struct ashmem_range { /* LRU list of unpinned pages, protected by ashmem_mutex */ static LIST_HEAD(ashmem_lru_list); +static atomic_t ashmem_shrink_inflight = ATOMIC_INIT(0); +static DECLARE_WAIT_QUEUE_HEAD(ashmem_shrink_wait); + /* * long lru_count - The count of pages on our LRU list. * @@ -438,7 +441,6 @@ static int ashmem_mmap(struct file *file, struct vm_area_struct *vma) static unsigned long ashmem_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) { - struct ashmem_range *range, *next; unsigned long freed = 0; /* We might recurse into filesystem code, so bail out if necessary */ @@ -448,17 +450,27 @@ static int ashmem_mmap(struct file *file, struct vm_area_struct *vma) if (!mutex_trylock(&ashmem_mutex)) return -1; - list_for_each_entry_safe(range, next, &ashmem_lru_list, lru) { + while (!list_empty(&ashmem_lru_list)) { + struct ashmem_range *range = + list_first_entry(&ashmem_lru_list, typeof(*range), lru); loff_t start = range->pgstart * PAGE_SIZE; loff_t end = (range->pgend + 1) * PAGE_SIZE; + struct file *f = range->asma->file; - range->asma->file->f_op->fallocate(range->asma->file, - FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, - start, end - start); + get_file(f); + atomic_inc(&ashmem_shrink_inflight); range->purged = ASHMEM_WAS_PURGED; lru_del(range); freed += range_size(range); + mutex_unlock(&ashmem_mutex); + f->f_op->fallocate(f, + FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, + start, end - start); + fput(f); + if (atomic_dec_and_test(&ashmem_shrink_inflight)) + wake_up_all(&ashmem_shrink_wait); + mutex_lock(&ashmem_mutex); if (--sc->nr_to_scan <= 0) break; } @@ -713,6 +725,7 @@ static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd, return -EFAULT; mutex_lock(&ashmem_mutex); + wait_event(ashmem_shrink_wait, !atomic_read(&ashmem_shrink_inflight)); if (!asma->file) goto out_unlock; -- 1.8.3.1