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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C25E2C433F5 for ; Sun, 10 Oct 2021 05:30:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A0A4660F57 for ; Sun, 10 Oct 2021 05:30:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230372AbhJJFbx (ORCPT ); Sun, 10 Oct 2021 01:31:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:59070 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230180AbhJJFbw (ORCPT ); Sun, 10 Oct 2021 01:31:52 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 4B969608FE; Sun, 10 Oct 2021 05:29:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1633843794; bh=eHFnTDoBrLpZXdBQbujr2Cswj6WvddXJYT4qVIu7jts=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=my+A/rdRN93FNGZhI3TpZWC6QVYpIPlOqBaadqubmF4PfP1rMeyf/Xl46E9v4UJeb 1d7fpHsWJ9Ymq6Qh1awQZUgK0IwJ1mUxVDmTxnkcE+c2i7Qk3gt2s6qPHv+D8og8rU 75pTIgEA7Ye4VXySMtCwt4uuzQXwotJ0xlVKOvNPfF8aTXaTyr1vkn788BkaWDzsyJ S2kD9rk3cJwAGTEazlUYBtfxUDcDdJlKTyV534v400GTDiEZVHh7WGhlcdvU/Y4l+8 5H42kzADfWKXAbPiRZJcYj1CeHkdbpyWKty93CEo1NNMeOt3z2w2PXh2axwVKEhaos naNlvC7lBiOOA== Date: Sun, 10 Oct 2021 08:29:48 +0300 From: Mike Rapoport To: Sean Christopherson Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, "Darrick J . Wong" , Stephen Subject: Re: [PATCH] mm: Fix NULL page->mapping dereference in page_is_secretmem() Message-ID: References: <20211007231502.3552715-1-seanjc@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211007231502.3552715-1-seanjc@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 07, 2021 at 04:15:02PM -0700, Sean Christopherson wrote: > Check for a NULL page->mapping before dereferencing the mapping in > page_is_secretmem(), as the page's mapping can be nullified while gup() > is running, e.g. by reclaim or truncation. > > BUG: kernel NULL pointer dereference, address: 0000000000000068 > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > PGD 0 P4D 0 > Oops: 0000 [#1] PREEMPT SMP NOPTI > CPU: 6 PID: 4173897 Comm: CPU 3/KVM Tainted: G W > RIP: 0010:internal_get_user_pages_fast+0x621/0x9d0 > Code: <48> 81 7a 68 80 08 04 bc 0f 85 21 ff ff 8 89 c7 be > RSP: 0018:ffffaa90087679b0 EFLAGS: 00010046 > RAX: ffffe3f37905b900 RBX: 00007f2dd561e000 RCX: ffffe3f37905b934 > RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffe3f37905b900 > ... > CR2: 0000000000000068 CR3: 00000004c5898003 CR4: 00000000001726e0 > Call Trace: > get_user_pages_fast_only+0x13/0x20 > hva_to_pfn+0xa9/0x3e0 > try_async_pf+0xa1/0x270 > direct_page_fault+0x113/0xad0 > kvm_mmu_page_fault+0x69/0x680 > vmx_handle_exit+0xe1/0x5d0 > kvm_arch_vcpu_ioctl_run+0xd81/0x1c70 > kvm_vcpu_ioctl+0x267/0x670 > __x64_sys_ioctl+0x83/0xa0 > do_syscall_64+0x56/0x80 > entry_SYSCALL_64_after_hwframe+0x44/0xae > > Cc: Mike Rapoport > Cc: linux-mm@kvack.org > Reported-by: Darrick J. Wong > Reported-by: Stephen > Tested-by: Darrick J. Wong > Signed-off-by: Sean Christopherson Reviewed-by: Mike Rapoport > --- > include/linux/secretmem.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/secretmem.h b/include/linux/secretmem.h > index 21c3771e6a56..988528b5da43 100644 > --- a/include/linux/secretmem.h > +++ b/include/linux/secretmem.h > @@ -23,7 +23,7 @@ static inline bool page_is_secretmem(struct page *page) > mapping = (struct address_space *) > ((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS); > > - if (mapping != page->mapping) > + if (!mapping || mapping != page->mapping) > return false; > > return mapping->a_ops == &secretmem_aops; > -- > 2.33.0.882.g93a45727a2-goog > -- Sincerely yours, Mike.