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[209.132.180.67]) by mx.google.com with ESMTP id o57si3595998edc.240.2019.11.24.11.32.05; Sun, 24 Nov 2019 11:32:40 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726921AbfKXTaq (ORCPT + 99 others); Sun, 24 Nov 2019 14:30:46 -0500 Received: from zeniv.linux.org.uk ([195.92.253.2]:51292 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726803AbfKXTaq (ORCPT ); Sun, 24 Nov 2019 14:30:46 -0500 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1iYxad-0005Jj-31; Sun, 24 Nov 2019 19:30:35 +0000 Date: Sun, 24 Nov 2019 19:30:35 +0000 From: Al Viro To: syzbot Cc: cmetcalf@ezchip.com, coreteam@netfilter.org, davem@davemloft.net, dvyukov@google.com, gang.chen.5i5j@gmail.com, kaber@trash.net, kadlec@blackhole.kfki.hu, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, netfilter-devel@vger.kernel.org, pablo@netfilter.org, syzkaller-bugs@googlegroups.com Subject: Re: KASAN: use-after-free Read in blkdev_get Message-ID: <20191124193035.GA4203@ZenIV.linux.org.uk> References: <000000000000e59aab056e8873ae@google.com> <0000000000000beff305981c5ac6@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0000000000000beff305981c5ac6@google.com> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Nov 24, 2019 at 11:07:00AM -0800, syzbot wrote: > syzbot has bisected this bug to: > > commit 77ef8f5177599efd0cedeb52c1950c1bd73fa5e3 > Author: Chris Metcalf > Date: Mon Jan 25 20:05:34 2016 +0000 > > tile kgdb: fix bug in copy to gdb regs, and optimize memset > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1131bc0ee00000 > start commit: f5b7769e Revert "debugfs: inode: debugfs_create_dir uses m.. > git tree: upstream > final crash: https://syzkaller.appspot.com/x/report.txt?x=1331bc0ee00000 > console output: https://syzkaller.appspot.com/x/log.txt?x=1531bc0ee00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=709f8187af941e84 > dashboard link: https://syzkaller.appspot.com/bug?extid=eaeb616d85c9a0afec7d > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=177f898f800000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=147eb85f800000 > > Reported-by: syzbot+eaeb616d85c9a0afec7d@syzkaller.appspotmail.com > Fixes: 77ef8f517759 ("tile kgdb: fix bug in copy to gdb regs, and optimize > memset") > > For information about bisection process see: https://goo.gl/tpsmEJ#bisection Seriously? How can the commit in question (limited to arch/tile/kernel/kgdb.c) possibly affect a bug that manages to produce a crash report with RSP: 0018:ffffffff82e03eb8 EFLAGS: 00000282 RAX: 0000000000000000 RBX: ffffffff82e00000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff81088779 RBP: ffffffff82e03eb8 R08: 0000000000000000 R09: 0000000000000001 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: ffffffff82e00000 FS: 0000000000000000(0000) GS:ffff88021fc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000c420447ff8 CR3: 0000000213184000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 in it? Unless something very odd has happened to tile, this crash has been observed on 64bit x86; the names of registers alone are enough to be certain of that. And the binaries produced by an x86 build should not be affected by any changes in arch/tile; not unless something is very wrong with the build system. It's not even that this commit has fixed an earlier bug that used to mask the one manifested here - it really should have had zero impact on x86 builds, period. So I'm sorry, but I'm calling bullshit. Something's quite wrong with the bot - either its build system or the bisection process.