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 4AA6CC433F5 for ; Tue, 7 Dec 2021 04:19:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A58A96B0085; Mon, 6 Dec 2021 23:19:45 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A07A76B0087; Mon, 6 Dec 2021 23:19:45 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8CFF76B0088; Mon, 6 Dec 2021 23:19:45 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0177.hostedemail.com [216.40.44.177]) by kanga.kvack.org (Postfix) with ESMTP id 7F1DA6B0085 for ; Mon, 6 Dec 2021 23:19:45 -0500 (EST) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 4C6F1894DE for ; Tue, 7 Dec 2021 04:19:35 +0000 (UTC) X-FDA: 78889694310.22.32F24EE Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf20.hostedemail.com (Postfix) with ESMTP id EAFD2D0000A2 for ; Tue, 7 Dec 2021 04:19:33 +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=eI/E/scurWRpXvQ4y7yg58dqUt9tO+R5AEVz3Yib1pI=; b=DsjLAg+kppkmLxuifRzHc7NCy+ 7q/TbExCf1+cP/NGmcZzF7pi4pa7Ey+X7+mffz+Tr+PYm9mr4ADH4yTGHSH+HpJ2qQu4roIj9FqW5 w7bF7HvrSbUxvMKTOVJp/5gd4xvURrn2OLxGlbXPXLQ/BKWvFPglN9+QB8fRxvGMGeFBriL2P1uGn dwpdvovNse2yinWIkp31hKT/ImTWfI622SNrPXR7zK8y6L3ncuo6ONQ+Hw2MwoyHa45nqvpzRlJ6i VhmpLM/Qhr04X1NKE7tPOvcdfoouDhhUJHMYofR81sWqMfQYyFg5bXnPTx08j5LeUEicumKjR7Bgc q7o/Blcw==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1muRww-006vYD-9T; Tue, 07 Dec 2021 04:19:30 +0000 Date: Tue, 7 Dec 2021 04:19:30 +0000 From: Matthew Wilcox To: Andrew Morton Cc: syzbot , linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, linux-f2fs-devel@lists.sourceforge.net Subject: Re: [syzbot] BUG: unable to handle kernel NULL pointer dereference in folio_mark_dirty Message-ID: References: <0000000000005f297e05d24f05f6@google.com> <20211206175631.5d0c3caefa96f0479f0fc2e8@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211206175631.5d0c3caefa96f0479f0fc2e8@linux-foundation.org> X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: EAFD2D0000A2 X-Stat-Signature: 1xqc6zfropwue8t7c85df186rbqtximb Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=DsjLAg+k; spf=none (imf20.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none X-HE-Tag: 1638850773-901732 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 Mon, Dec 06, 2021 at 05:56:31PM -0800, Andrew Morton wrote: > > BUG: kernel NULL pointer dereference, address: 0000000000000000 > > cc linux-f2fs-devel@lists.sourceforge.net > > And willy, who might help with diagnosing this. But it does seem that > f2fs got itself a NULL page* then put it in places where it shouldn't have. I'm surprised it got that far. void f2fs_update_meta_page(struct f2fs_sb_info *sbi, void *src, block_t blk_addr) { struct page *page = f2fs_grab_meta_page(sbi, blk_addr); memcpy(page_address(page), src, PAGE_SIZE); set_page_dirty(page); f2fs_put_page(page, 1); } How does page_address(NULL) not crash first? Or return an address that can be the target of a memcpy()? > > #PF: supervisor instruction fetch in kernel mode > > #PF: error_code(0x0010) - not-present page > > PGD 70764067 P4D 70764067 PUD 0 > > Oops: 0010 [#1] PREEMPT SMP KASAN > > CPU: 1 PID: 6541 Comm: syz-executor.3 Not tainted 5.16.0-rc3-syzkaller #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > RIP: 0010:0x0 > > Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6. > > RSP: 0018:ffffc900027ff7f8 EFLAGS: 00010246 > > RAX: 1ffffffff14fef03 RBX: ffffffff8a7f7818 RCX: ffff88801b40d700 > > RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffea0002790ec0 > > RBP: dffffc0000000000 R08: ffffffff81b0fa16 R09: fffff940004f21d9 > > R10: fffff940004f21d9 R11: 0000000000000000 R12: ffff88806c11c7b0 > > R13: 0000000000000000 R14: 1ffffd40004f21d9 R15: ffffea0002790ec0 > > FS: 0000555557165400(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: ffffffffffffffd6 CR3: 0000000030d85000 CR4: 00000000003526e0 > > Call Trace: > > > > folio_mark_dirty+0x136/0x270 mm/page-writeback.c:2639 > > f2fs_update_meta_page+0x4b/0x380 fs/f2fs/segment.c:2485 > > do_checkpoint fs/f2fs/checkpoint.c:1513 [inline] > > f2fs_write_checkpoint+0x31ad/0x5430 fs/f2fs/checkpoint.c:1674 > > f2fs_issue_checkpoint+0x361/0x4e0 > > sync_filesystem+0x19c/0x1f0 fs/sync.c:63 > > generic_shutdown_super+0x6b/0x300 fs/super.c:448 > > kill_block_super+0x79/0xd0 fs/super.c:1397 > > kill_f2fs_super+0x2f9/0x3c0 fs/f2fs/super.c:4478 > > deactivate_locked_super+0xa7/0xf0 fs/super.c:335 > > cleanup_mnt+0x462/0x510 fs/namespace.c:1137 > > task_work_run+0x146/0x1c0 kernel/task_work.c:164 > > tracehook_notify_resume include/linux/tracehook.h:189 [inline] > > exit_to_user_mode_loop kernel/entry/common.c:175 [inline] > > exit_to_user_mode_prepare+0x209/0x220 kernel/entry/common.c:207 > > __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline] > > syscall_exit_to_user_mode+0x2e/0x70 kernel/entry/common.c:300 > > do_syscall_64+0x53/0xd0 arch/x86/entry/common.c:86 > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > RIP: 0033:0x7f6cfdd59f57 > > Code: ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 > > RSP: 002b:00007fffcbddcad8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6 > > RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f6cfdd59f57 > > RDX: 00007fffcbddcbac RSI: 000000000000000a RDI: 00007fffcbddcba0 > > RBP: 00007fffcbddcba0 R08: 00000000ffffffff R09: 00007fffcbddc970 > > R10: 0000555557166903 R11: 0000000000000246 R12: 00007f6cfddb2105 > > R13: 00007fffcbdddc60 R14: 0000555557166810 R15: 00007fffcbdddca0 > > > > Modules linked in: > > CR2: 0000000000000000 > > ---[ end trace 08eda5a5e35b48a0 ]--- > > RIP: 0010:0x0 > > Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6. > > RSP: 0018:ffffc900027ff7f8 EFLAGS: 00010246 > > RAX: 1ffffffff14fef03 RBX: ffffffff8a7f7818 RCX: ffff88801b40d700 > > RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffea0002790ec0 > > RBP: dffffc0000000000 R08: ffffffff81b0fa16 R09: fffff940004f21d9 > > R10: fffff940004f21d9 R11: 0000000000000000 R12: ffff88806c11c7b0 > > R13: 0000000000000000 R14: 1ffffd40004f21d9 R15: ffffea0002790ec0 > > FS: 0000555557165400(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: ffffffffffffffd6 CR3: 0000000030d85000 CR4: 00000000003526e0 > > > > > > --- > > 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.