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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 34554C433EF for ; Thu, 7 Jul 2022 20:28:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235937AbiGGU2V (ORCPT ); Thu, 7 Jul 2022 16:28:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60082 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235709AbiGGU2U (ORCPT ); Thu, 7 Jul 2022 16:28:20 -0400 Received: from mail-il1-x12a.google.com (mail-il1-x12a.google.com [IPv6:2607:f8b0:4864:20::12a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 735762A94D for ; Thu, 7 Jul 2022 13:28:19 -0700 (PDT) Received: by mail-il1-x12a.google.com with SMTP id v2so2671789ilo.7 for ; Thu, 07 Jul 2022 13:28:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=lnPdki3U1HzYs0CImjis2nyJH9ZY1bhBPOIDGHPVDrw=; b=f/+n6NnnOyy+rz5DYYmTw3B1MCd7fk1PKnsKmvCKhWZP/bR9y/KKqqJ8Hr9inQZVf9 eG6YeqBRj95B8m2MJjUWSusb2rDPoyiYVSw1hGcy8U6Gn18T0rQa0LWDy71kyXfqX9Ig dk3MJJHrEqf11QvXorsaV5z4I4iKUayii5z9k7cJCx9s5PeJB0eeKFejQWwZGgo+irbt vSv3tVDn/7R0Qiu/rmi14L0Ij/G5v1pmCd3qLg8dyC1jXRel+CbF750in+IL5G+NR2oL q1XcKnOTm5YPZfOyX2Y7WXezKSs8AFyk8sfQi/ZCNsxAED5oyGlpTwiGoBIF52u3U90X NQIg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=lnPdki3U1HzYs0CImjis2nyJH9ZY1bhBPOIDGHPVDrw=; b=MNNiyroLWFOs1zlVA6hgYOOIISrDUjCGkvLL/j4xV9CF+a6KTgkeinZDr5M0DPwQx9 LJCvZbzGFF2P3eSoBlKHBGCuCe7PXVsbczViqn7ZuAJB0F2oPvi56aGnGFC3o0LnScJf btu51Ygety2B70XoulVt92BwPvdvaBubh3w7YR1hOze2a5wC89Cj1KF3rOIB7sGTCI4e PU/1W5uZsWk7zxKrBeTIzypRbpCe+uq5dNOJPX417GSba4P+IPlVC1vaAn1d/3W5MsV2 kTSYRYmo+1iK+caHFnITjnq6eYivic20oaDpRotSGesuwlf6pHwRPglgnyg0NRc5Xdbk zShw== X-Gm-Message-State: AJIora/tu9QqSCOPFrIFrCNRLyWMUB1kzSpn8GsIUtfuPUBRF6EqwcI3 y6UWIEZCcrvK955vhRZof8Kck5vNgbFeLFvCdi7L+Q== X-Google-Smtp-Source: AGRyM1tM/KnkuQVig9sLggudWlxS0l+TZ6ubWAAz8YA3uJntlv3Ha8v/eItGrj3jm2fMpqn8xenn2fg11jZjfISsrbQ= X-Received: by 2002:a92:a801:0:b0:2da:b79f:777 with SMTP id o1-20020a92a801000000b002dab79f0777mr28719684ilh.275.1657225698668; Thu, 07 Jul 2022 13:28:18 -0700 (PDT) MIME-Version: 1.0 References: <20220707165650.248088-1-rppt@kernel.org> In-Reply-To: <20220707165650.248088-1-rppt@kernel.org> From: Axel Rasmussen Date: Thu, 7 Jul 2022 13:27:42 -0700 Message-ID: Subject: Re: [PATCH v2] secretmem: fix unhandled fault in truncate To: Mike Rapoport Cc: Andrew Morton , Eric Biggers , Hillf Danton , Matthew Wilcox , Mike Rapoport , linux-fsdevel , Linux MM , syzkaller-bugs@googlegroups.com, syzbot Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Looks correct to me - at least, I'm confident it will prevent the race. I'm not really familiar enough with filesystem APIs to know whether Yang's suggestion is better or not, though. Reviewed-by: Axel Rasmussen On Thu, Jul 7, 2022 at 9:57 AM Mike Rapoport wrote: > > From: Mike Rapoport > > syzkaller reports the following issue: > > BUG: unable to handle page fault for address: ffff888021f7e005 > PGD 11401067 P4D 11401067 PUD 11402067 PMD 21f7d063 PTE 800fffffde081060 > Oops: 0002 [#1] PREEMPT SMP KASAN > CPU: 0 PID: 3761 Comm: syz-executor281 Not tainted 5.19.0-rc4-syzkaller-00014-g941e3e791269 #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > RIP: 0010:memset_erms+0x9/0x10 arch/x86/lib/memset_64.S:64 > Code: c1 e9 03 40 0f b6 f6 48 b8 01 01 01 01 01 01 01 01 48 0f af c6 f3 48 ab 89 d1 f3 aa 4c 89 c8 c3 90 49 89 f9 40 88 f0 48 89 d1 aa 4c 89 c8 c3 90 49 89 fa 40 0f b6 ce 48 b8 01 01 01 01 01 01 > RSP: 0018:ffffc9000329fa90 EFLAGS: 00010202 > RAX: 0000000000000000 RBX: 0000000000001000 RCX: 0000000000000ffb > RDX: 0000000000000ffb RSI: 0000000000000000 RDI: ffff888021f7e005 > RBP: ffffea000087df80 R08: 0000000000000001 R09: ffff888021f7e005 > R10: ffffed10043efdff R11: 0000000000000000 R12: 0000000000000005 > R13: 0000000000000000 R14: 0000000000001000 R15: 0000000000000ffb > FS: 00007fb29d8b2700(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: ffff888021f7e005 CR3: 0000000026e7b000 CR4: 00000000003506f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > > zero_user_segments include/linux/highmem.h:272 [inline] > folio_zero_range include/linux/highmem.h:428 [inline] > truncate_inode_partial_folio+0x76a/0xdf0 mm/truncate.c:237 > truncate_inode_pages_range+0x83b/0x1530 mm/truncate.c:381 > truncate_inode_pages mm/truncate.c:452 [inline] > truncate_pagecache+0x63/0x90 mm/truncate.c:753 > simple_setattr+0xed/0x110 fs/libfs.c:535 > secretmem_setattr+0xae/0xf0 mm/secretmem.c:170 > notify_change+0xb8c/0x12b0 fs/attr.c:424 > do_truncate+0x13c/0x200 fs/open.c:65 > do_sys_ftruncate+0x536/0x730 fs/open.c:193 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x46/0xb0 > RIP: 0033:0x7fb29d900899 > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007fb29d8b2318 EFLAGS: 00000246 ORIG_RAX: 000000000000004d > RAX: ffffffffffffffda RBX: 00007fb29d988408 RCX: 00007fb29d900899 > RDX: 00007fb29d900899 RSI: 0000000000000005 RDI: 0000000000000003 > RBP: 00007fb29d988400 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 00007fb29d98840c > R13: 00007ffca01a23bf R14: 00007fb29d8b2400 R15: 0000000000022000 > > Modules linked in: > CR2: ffff888021f7e005 > ---[ end trace 0000000000000000 ]--- > > Eric Biggers suggested that this happens when > secretmem_setattr()->simple_setattr() races with secretmem_fault() so > that a page that is faulted in by secretmem_fault() (and thus removed > from the direct map) is zeroed by inode truncation right afterwards. > > Since do_truncate() takes inode_lock(), adding inode_lock_shared() to > secretmem_fault() prevents the race. > > Reported-by: syzbot+9bd2b7adbd34b30b87e4@syzkaller.appspotmail.com > Suggested-by: Eric Biggers > Signed-off-by: Mike Rapoport > --- > > v2: use inode_lock_shared() rather than add a new rw_sem to secretmem > > Axel, I didn't add your Reviewed-by because v2 is quite different. > > mm/secretmem.c | 21 ++++++++++++++++----- > 1 file changed, 16 insertions(+), 5 deletions(-) > > diff --git a/mm/secretmem.c b/mm/secretmem.c > index 206ed6b40c1d..a4fabf705e4f 100644 > --- a/mm/secretmem.c > +++ b/mm/secretmem.c > @@ -55,22 +55,28 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf) > gfp_t gfp = vmf->gfp_mask; > unsigned long addr; > struct page *page; > + vm_fault_t ret; > int err; > > if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode)) > return vmf_error(-EINVAL); > > + inode_lock_shared(inode); > + > retry: > page = find_lock_page(mapping, offset); > if (!page) { > page = alloc_page(gfp | __GFP_ZERO); > - if (!page) > - return VM_FAULT_OOM; > + if (!page) { > + ret = VM_FAULT_OOM; > + goto out; > + } > > err = set_direct_map_invalid_noflush(page); > if (err) { > put_page(page); > - return vmf_error(err); > + ret = vmf_error(err); > + goto out; > } > > __SetPageUptodate(page); > @@ -86,7 +92,8 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf) > if (err == -EEXIST) > goto retry; > > - return vmf_error(err); > + ret = vmf_error(err); > + goto out; > } > > addr = (unsigned long)page_address(page); > @@ -94,7 +101,11 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf) > } > > vmf->page = page; > - return VM_FAULT_LOCKED; > + ret = VM_FAULT_LOCKED; > + > +out: > + inode_unlock_shared(inode); > + return ret; > } > > static const struct vm_operations_struct secretmem_vm_ops = { > > base-commit: 03c765b0e3b4cb5063276b086c76f7a612856a9a > -- > 2.34.1 >