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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 20DE3C3A59E for ; Sun, 25 Aug 2019 00:55:00 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id CE94D22CE3 for ; Sun, 25 Aug 2019 00:54:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="wpzfkNyX" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CE94D22CE3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 80D026B0501; Sat, 24 Aug 2019 20:54:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7BD2C6B0503; Sat, 24 Aug 2019 20:54:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6D42D6B0504; Sat, 24 Aug 2019 20:54:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0048.hostedemail.com [216.40.44.48]) by kanga.kvack.org (Postfix) with ESMTP id 4ADCA6B0501 for ; Sat, 24 Aug 2019 20:54:59 -0400 (EDT) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id E6050824CA26 for ; Sun, 25 Aug 2019 00:54:58 +0000 (UTC) X-FDA: 75859130676.15.heat71_488d6cc564a25 X-HE-Tag: heat71_488d6cc564a25 X-Filterd-Recvd-Size: 4090 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf18.hostedemail.com (Postfix) with ESMTP for ; Sun, 25 Aug 2019 00:54:58 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 186B42339D; Sun, 25 Aug 2019 00:54:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566694497; bh=T03GOG6VGUuHs/Ca4qtKoTZFfuRB7+LZvKLzqSSOIhE=; h=Date:From:To:Subject:From; b=wpzfkNyXyN6ka6oSUQAmEWmPWf6KlANw+++YxBJbJr0fJT8pQH6291yLe+FT/sBTs ZFjVEIoWisA8s7huPfNBNTrreGtifYfUWDjF0yWHvItWQgHxhG0/FkT/J9aSt/Ez3f KGorxLIlwJn6IjjCAwxvf42aQ9EgLhsTZkUfxR9A= Date: Sat, 24 Aug 2019 17:54:56 -0700 From: akpm@linux-foundation.org To: aarcange@redhat.com, akpm@linux-foundation.org, jannh@google.com, jgg@mellanox.com, linux-mm@kvack.org, mhocko@suse.com, mm-commits@vger.kernel.org, oleg@redhat.com, penguin-kernel@I-love.SAKURA.ne.jp, peterx@redhat.com, rppt@linux.ibm.com, stable@vger.kernel.org, torvalds@linux-foundation.org, wangkefeng.wang@huawei.com Subject: [patch 07/11] userfaultfd_release: always remove uffd flags and clear vm_userfaultfd_ctx Message-ID: <20190825005456.L2ZisNIcB%akpm@linux-foundation.org> User-Agent: s-nail v14.8.16 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: From: Oleg Nesterov Subject: userfaultfd_release: always remove uffd flags and clear vm_userfaultfd_ctx userfaultfd_release() should clear vm_flags/vm_userfaultfd_ctx even if mm->core_state != NULL. Otherwise a page fault can see userfaultfd_missing() == T and use an already freed userfaultfd_ctx. Link: http://lkml.kernel.org/r/20190820160237.GB4983@redhat.com Fixes: 04f5866e41fb ("coredump: fix race condition between mmget_not_zero()/get_task_mm() and core dumping") Signed-off-by: Oleg Nesterov Reported-by: Kefeng Wang Reviewed-by: Andrea Arcangeli Tested-by: Kefeng Wang Cc: Peter Xu Cc: Mike Rapoport Cc: Jann Horn Cc: Jason Gunthorpe Cc: Michal Hocko Cc: Tetsuo Handa Cc: Signed-off-by: Andrew Morton --- fs/userfaultfd.c | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-) --- a/fs/userfaultfd.c~userfaultfd_release-always-remove-uffd-flags-and-clear-vm_userfaultfd_ctx +++ a/fs/userfaultfd.c @@ -880,6 +880,7 @@ static int userfaultfd_release(struct in /* len == 0 means wake all */ struct userfaultfd_wake_range range = { .len = 0, }; unsigned long new_flags; + bool still_valid; WRITE_ONCE(ctx->released, true); @@ -895,8 +896,7 @@ static int userfaultfd_release(struct in * taking the mmap_sem for writing. */ down_write(&mm->mmap_sem); - if (!mmget_still_valid(mm)) - goto skip_mm; + still_valid = mmget_still_valid(mm); prev = NULL; for (vma = mm->mmap; vma; vma = vma->vm_next) { cond_resched(); @@ -907,19 +907,20 @@ static int userfaultfd_release(struct in continue; } new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP); - prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end, - new_flags, vma->anon_vma, - vma->vm_file, vma->vm_pgoff, - vma_policy(vma), - NULL_VM_UFFD_CTX); - if (prev) - vma = prev; - else - prev = vma; + if (still_valid) { + prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end, + new_flags, vma->anon_vma, + vma->vm_file, vma->vm_pgoff, + vma_policy(vma), + NULL_VM_UFFD_CTX); + if (prev) + vma = prev; + else + prev = vma; + } vma->vm_flags = new_flags; vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; } -skip_mm: up_write(&mm->mmap_sem); mmput(mm); wakeup: _