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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id EA7BFC433EF for ; Sat, 18 Jun 2022 00:14:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 406C06B0071; Fri, 17 Jun 2022 20:14:15 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3B6DD6B0073; Fri, 17 Jun 2022 20:14:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 256B46B0074; Fri, 17 Jun 2022 20:14:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 143CA6B0071 for ; Fri, 17 Jun 2022 20:14:15 -0400 (EDT) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id CCC79A13 for ; Sat, 18 Jun 2022 00:14:14 +0000 (UTC) X-FDA: 79589434428.11.C14F87D Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf25.hostedemail.com (Postfix) with ESMTP id C89E7A0093 for ; Sat, 18 Jun 2022 00:14:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=rPWgXLV8K16cesVI1X55HPbm3k5YAgm6gxtiFN3IGl8=; b=km4a+Fh3vIl+R9fBcZBqk3xepD 6oZ3Oc4DyffY4QZR8yqIAZ36u5h+svAuqGkLeNNpcwFoyys3BCMv6XlNYtyJVeQL7JuzN1ehRhmsy s2w3fOtdUvDIMTGUKgtoblf6ZYSujDU4ld0hiDpO/HjujznEbvF/ZbuXEV2znSgpdDs3N0Isupylh a86WglC+70Wh+tJ//6DtOjE2RD15oJ2ECbS+J5Jocrxp8hPGx3FSVf9ax0+4ielTnTdfZMlOumNnW pb6wy0flOWcmyn6CR035doGzlMPMIzHP5spDkX8kjoBJbHHmaXv1uzol+X7L+0arJugYderiRzaGa r3UZcm5Q==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1o2M6K-003FA6-3d; Sat, 18 Jun 2022 00:14:08 +0000 Date: Sat, 18 Jun 2022 01:14:08 +0100 From: Matthew Wilcox To: Andrew Morton Cc: syzbot , linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, Yang Shi Subject: Re: [syzbot] KASAN: null-ptr-deref Read in hugepage_vma_check Message-ID: References: <0000000000003189f305e19f5d3e@google.com> <20220617165256.b5b9b257b30bc1dbb21fc8c6@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220617165256.b5b9b257b30bc1dbb21fc8c6@linux-foundation.org> ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1655511254; a=rsa-sha256; cv=none; b=UqrxusSITnRhldsB9tX44EfxHW6wUjZ6UGs8bcvfgcaBeFu9lgH4P6eIKuMzivu1uS49Hg aG09Dlqmuw/ps5jVacW/+pCzkPEDvsmFLHmROD5eRJJ2FfpbgzOhZWy3Zr1mOtPKlfSbWJ KtMycdJ9qRiWbc4cadKUmob+1fOwyR8= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=km4a+Fh3; dmarc=none; spf=none (imf25.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1655511254; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=rPWgXLV8K16cesVI1X55HPbm3k5YAgm6gxtiFN3IGl8=; b=58Bb4+toH/G8vsmmPsr5SkIYaAlWCYxWMMzRxv1UUgry1bgKxNpotDKcNdz7UBe8PHwLDk WVVSQgwLVL3rf9sImoZe00G4yt9fvWT1ncpt6MmvwDCNW16P7Un/FFvRcLrWKxS4DTju+7 ZP2pRMMuDV+qre2TQY3jcxg02KfSe8E= X-Rspamd-Queue-Id: C89E7A0093 X-Rspam-User: Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=km4a+Fh3; dmarc=none; spf=none (imf25.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org X-Rspamd-Server: rspam06 X-Stat-Signature: wajdz7usypnwjzab7a43jiw5qsz8wufj X-HE-Tag: 1655511253-841039 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: On Fri, Jun 17, 2022 at 04:52:56PM -0700, Andrew Morton wrote: > On Fri, 17 Jun 2022 00:04:23 -0700 syzbot wrote: > > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: c6d7e3b385f1 Add linux-next specific files for 20220616 > > git tree: linux-next > > console output: https://syzkaller.appspot.com/x/log.txt?x=10d9fb1bf00000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=9d495405e4a98620 > > dashboard link: https://syzkaller.appspot.com/bug?extid=4d875b4d2e2b60bae9b4 > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > > > > Unfortunately, I don't have any reproducer for this issue yet. > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+4d875b4d2e2b60bae9b4@syzkaller.appspotmail.com > > > > ================================================================== > > BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:71 [inline] > > BUG: KASAN: null-ptr-deref in test_bit include/asm-generic/bitops/instrumented-non-atomic.h:134 [inline] > > BUG: KASAN: null-ptr-deref in hugepage_vma_check+0x8e/0x750 mm/huge_memory.c:82 > > Read of size 8 at addr 00000000000005a8 by task syz-executor.5/21978 > > vma->vm_mm is NULL in show_smap->hugepage_vma_check(). > > Perhaps m_start() should be checking the mm after taking > mmap_read_lock() instead of before? > > Matthew, you mucked with it last ;) Can you please take a look? I think this is Yang Shi's fault. The last patch in that series which touches this area does: seq_printf(m, "THPeligible: %d\n", - hugepage_vma_check(vma, vma->vm_flags, true)); + hugepage_vma_check(vma, vma->vm_flags, true, false)); and hugepage_vma_check() does: if ((vm_flags & VM_NOHUGEPAGE) || test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) return false; Before those patches, it calls transparent_hugepage_active() which does not (afaict) touch vma->vm_mm. I haven't been paying attention to that patch series, so I don't have a constructive suggestion for how to fix. > > CPU: 0 PID: 21978 Comm: syz-executor.5 Not tainted 5.19.0-rc2-next-20220616-syzkaller #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > Call Trace: > > > > __dump_stack lib/dump_stack.c:88 [inline] > > dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 > > kasan_report+0xbe/0x1f0 mm/kasan/report.c:495 > > check_region_inline mm/kasan/generic.c:183 [inline] > > kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189 > > instrument_atomic_read include/linux/instrumented.h:71 [inline] > > test_bit include/asm-generic/bitops/instrumented-non-atomic.h:134 [inline] > > hugepage_vma_check+0x8e/0x750 mm/huge_memory.c:82 > > show_smap+0x1c6/0x470 fs/proc/task_mmu.c:866 > > traverse.part.0+0xcf/0x5f0 fs/seq_file.c:111 > > traverse fs/seq_file.c:101 [inline] > > seq_read_iter+0x90f/0x1280 fs/seq_file.c:195 > > seq_read+0x337/0x4b0 fs/seq_file.c:162 > > do_loop_readv_writev fs/read_write.c:763 [inline] > > do_loop_readv_writev fs/read_write.c:750 [inline] > > do_iter_read+0x4f8/0x750 fs/read_write.c:805 > > vfs_readv+0xe5/0x150 fs/read_write.c:923 > > do_preadv fs/read_write.c:1015 [inline] > > __do_sys_preadv fs/read_write.c:1065 [inline] > > __se_sys_preadv fs/read_write.c:1060 [inline] > > __x64_sys_preadv+0x22b/0x310 fs/read_write.c:1060 > > 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: 0033:0x7f5c1d889109 > > Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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:00007f5c1ea69168 EFLAGS: 00000246 ORIG_RAX: 0000000000000127 > > RAX: ffffffffffffffda RBX: 00007f5c1d99bf60 RCX: 00007f5c1d889109 > > RDX: 0000000000000001 RSI: 00000000200006c0 RDI: 0000000000000005 > > RBP: 00007f5c1d8e305d R08: 0000000000000000 R09: 0000000000000000 > > R10: 00000000fffffffe R11: 0000000000000246 R12: 0000000000000000 > > R13: 00007ffd8514b43f R14: 00007f5c1ea69300 R15: 0000000000022000 > > > > ================================================================== > > > > > > --- > > This report is generated by a bot. It may contain errors. > > See https://goo.gl/tpsmEJ for more information about syzbot. > > syzbot engineers can be reached at syzkaller@googlegroups.com. > > > > syzbot will keep track of this issue. See: > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.