From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Mon, 7 May 2018 23:56:26 -0400 From: "Theodore Y. Ts'o" To: Tetsuo Handa Cc: axboe@kernel.dk, syzkaller-bugs@googlegroups.com, linux-block@vger.kernel.org Subject: Re: [PATCH] loop: add recursion validation to LOOP_CHANGE_FD Message-ID: <20180508035626.GF999@thunk.org> References: <201805080545.HAF30756.QJOFOHFtSVMFLO@I-love.SAKURA.ne.jp> <20180507235142.GC999@thunk.org> <201805080028.w480SH3m013943@www262.sakura.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <201805080028.w480SH3m013943@www262.sakura.ne.jp> List-ID: On Tue, May 08, 2018 at 09:28:17AM +0900, Tetsuo Handa wrote: > The thread I mean is: > > general protection fault in lo_ioctl (2) > https://syzkaller.appspot.com/bug?id=f3cfe26e785d85f9ee259f385515291d21bd80a3 > > Are you sure that your patch solves this problem as well? Well, I can't be sure, since there's not enough information in that particular syzkaller report to definitively pin down the root cause. And while I can't reproduce the crash using the syzkaller repro with the patch; I can't reproduce the crash *without* the patch, either. This is what Syzkaller has to say, but of course, in its own documentation's words, "It's only a dumb bot". :-)e That being said, triggering the problem which it is so concerned about requires root privilieges, so I would not consider it high priority to track down --- especially given that we don't have a reliable reproducer for it. - Ted Hello, syzbot has tested the proposed patch and the reproducer did not trigger crash: Reported-and-tested-by: syzbot+bf89c128e05dd6c62523@syzkaller.appspotmail.com Tested on: commit: 170785a9cc72 loop: add recursion validation to LOOP_CHANGE.. git tree: git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git/loop-fix kernel config: https://syzkaller.appspot.com/x/.config?x=5a1dc06635c10d27 compiler: gcc (GCC) 8.0.1 20180413 (experimental) userspace arch: i386 Note: testing is done by a robot and is best-effort only.