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=-6.8 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,USER_AGENT_GIT autolearn=ham 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 BDEE7C3A5A3 for ; Tue, 27 Aug 2019 08:05:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8FF622173E for ; Tue, 27 Aug 2019 08:05:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566893114; bh=iwuGrLWUMKW5wHgT4YRHt6g8fhC4A8Gap1pgl9eBhXc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=iZQ8N1Aiv7zzoAFlvf1Ck+4TskQoq4IRDGY++rpTTzZV2R+VukczNKnkzOl7RKHzE dll9CdvpuGZnp7KoJkxy+irEhNwRo3QVhfJ90U6IQcV1/eUUIxzxWc4K9EB9qdwLtp EiPlVNMJWTuqlLbSBaCL4VC8TfI9zJwlLqkBe6OE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732720AbfH0IFN (ORCPT ); Tue, 27 Aug 2019 04:05:13 -0400 Received: from mail.kernel.org ([198.145.29.99]:34826 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731493AbfH0IFM (ORCPT ); Tue, 27 Aug 2019 04:05:12 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 C1DC1206BA; Tue, 27 Aug 2019 08:05:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566893111; bh=iwuGrLWUMKW5wHgT4YRHt6g8fhC4A8Gap1pgl9eBhXc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FzUrBMiS3n5tBbIjCOn+aDQ53yuwjwpJAntCvrOE8bxpW+ITFD+3Yqcbb4XXzf2bO ydU9WX7w+Z3Tb6nie+uP4+M4iVpG+YtNYXiuNJU2nmg4LN+gJpfgbiV3JIkNqETSiz 1jdU2albJlMnYIiblItnn2v/79AxsuBjZEk1vEMo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Oleg Nesterov , Kefeng Wang , Andrea Arcangeli , Peter Xu , Mike Rapoport , Jann Horn , Jason Gunthorpe , Michal Hocko , Tetsuo Handa , Andrew Morton , Linus Torvalds Subject: [PATCH 5.2 124/162] userfaultfd_release: always remove uffd flags and clear vm_userfaultfd_ctx Date: Tue, 27 Aug 2019 09:50:52 +0200 Message-Id: <20190827072742.800035960@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190827072738.093683223@linuxfoundation.org> References: <20190827072738.093683223@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Oleg Nesterov commit 46d0b24c5ee10a15dfb25e20642f5a5ed59c5003 upstream. 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 Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/userfaultfd.c | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-) --- a/fs/userfaultfd.c +++ b/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: