From patchwork Fri Oct 2 11:20:53 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andy Whitcroft X-Patchwork-Id: 525460 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) by ozlabs.org (Postfix) with ESMTP id 8FACE1402F0; Fri, 2 Oct 2015 21:21:19 +1000 (AEST) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.76) (envelope-from ) id 1ZhyOn-0000XE-KL; Fri, 02 Oct 2015 11:21:13 +0000 Received: from mail-wi0-f174.google.com ([209.85.212.174]) by huckleberry.canonical.com with esmtp (Exim 4.76) (envelope-from ) id 1ZhyOZ-0000NG-10 for kernel-team@lists.ubuntu.com; Fri, 02 Oct 2015 11:20:59 +0000 Received: by wiclk2 with SMTP id lk2so26649000wic.1 for ; Fri, 02 Oct 2015 04:20:58 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=3pYYzLIUI+W2Wt0K6gheuDwh8TyTJe+D6HXY+xzeJyg=; b=H1mMkXCfKsyEHGm6yJsW4V/LZjl9kYQ7IN8yDnzF8gu5GoBH7v/SFyQBlG+biUPVeC vGPwmJMNgPxn3V7nRbT5L0vpIneknWDvhfJac6U4PpbtC5dKULC4trtBy4lqoZdcaXrj fkKVJilDuw0JQ82PBUjQdmdzukC1dCpwpDNNq/xMSV88PIPd4QdBWEMLMYK7sqXiHvC2 GLzn0VSljgpRFUQR1zqcsbhwBezfX/u7ZPEjZYNmtlNv6DnVMx04YyWMBNSRFGPB+DF8 P+Wwt5G26PxrBgwFnbHpXpIIZCmzGFe+olmMF87vLbWTBI4/V4UrhsTtzachfeIPR/zR Wp3A== X-Gm-Message-State: ALoCoQnO7Dx4QmO9Ya5qwWNTLNzUWuLvWmrEr9JK7nyn77wh/tQNC7479l1/EclZEij05f6YrX36 X-Received: by 10.194.63.5 with SMTP id c5mr15158780wjs.127.1443784858808; Fri, 02 Oct 2015 04:20:58 -0700 (PDT) Received: from localhost ([2001:470:6973:2:cde0:bb8:21a1:928c]) by smtp.gmail.com with ESMTPSA id go5sm7909584wib.3.2015.10.02.04.20.58 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 02 Oct 2015 04:20:58 -0700 (PDT) From: Andy Whitcroft To: kernel-team@lists.ubuntu.com Subject: [trusty/master-next 1/1] UBUNTU: SAUCE: aufs3: mmap: Fix races in madvise_remove() and sys_msync() Date: Fri, 2 Oct 2015 12:20:53 +0100 Message-Id: <1443784854-29493-3-git-send-email-apw@canonical.com> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1443784854-29493-1-git-send-email-apw@canonical.com> References: <1443784854-29493-1-git-send-email-apw@canonical.com> Cc: Andy Whitcroft X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.14 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: kernel-team-bounces@lists.ubuntu.com From: Ben Hutchings In madvise_remove() and sys_msync() we drop the mmap_sem before dropping references to the mapped file(s). As soon as we drop the mmap_sem, the vma we got them from might be destroyed by another thread, so calling vma_do_fput() is a possible use-after-free. In these cases we don't actually need a reference to the aufs file, so revert to using get_file() and fput() directly. Bug-Link: https://bugs.debian.org/796036 CVE-2015-7312 Signed-off-by: Ben Hutchings Signed-off-by: Andy Whitcroft --- mm/madvise.c | 4 ++-- mm/msync.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/mm/madvise.c b/mm/madvise.c index 5e700b1..e0504c4 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -327,12 +327,12 @@ static long madvise_remove(struct vm_area_struct *vma, * vma's reference to the file) can go away as soon as we drop * mmap_sem. */ - vma_get_file(vma); + get_file(vma); up_read(¤t->mm->mmap_sem); error = do_fallocate(f, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, offset, end - start); - vma_fput(vma); + fput(vma); down_read(¤t->mm->mmap_sem); return error; } diff --git a/mm/msync.c b/mm/msync.c index 02d770e..b2d70d9 100644 --- a/mm/msync.c +++ b/mm/msync.c @@ -80,10 +80,10 @@ SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags) start = vma->vm_end; if ((flags & MS_SYNC) && file && (vma->vm_flags & VM_SHARED)) { - vma_get_file(vma); + get_file(vma); up_read(&mm->mmap_sem); error = vfs_fsync(file, 0); - vma_fput(vma); + fput(vma); if (error || start >= end) goto out; down_read(&mm->mmap_sem);