From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4973415BE for ; Sat, 11 Nov 2023 00:55:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=mit.edu header.i=@mit.edu header.b="AYRe7Uyd" Received: from outgoing.mit.edu (outgoing-auth-1.mit.edu [18.9.28.11]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 086DB448C for ; Fri, 10 Nov 2023 16:55:26 -0800 (PST) Received: from letrec.thunk.org ([172.59.192.143]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 3AB0t1E0028402 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 10 Nov 2023 19:55:04 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mit.edu; s=outgoing; t=1699664106; bh=KGrCo0EAEmidC19jfpkh83o8LjlI6ymESMr0sKB5j0A=; h=Date:From:Subject:Message-ID:MIME-Version:Content-Type; b=AYRe7UydBBubaW7sb4UEwm3rmq27RLIsAOoGYn0bEqX7/1DTOMjg7JEYiRuecpWUu 7joHrfDoCZgZ+z0fM+sK4zbQEbH0/f5MSfb/7Od0HMKHh+iMIh/q1v27UC+YzDH3Ku sOUC7BVviAOJ3CkkKDHQ34vjxSEPgA4FCQ34q/lKT8G8KlaXP3X8rL83TD+W05shQ6 ZZTJGugsZMvxTe8DJ6gEjYxKX747cZtJvG0LmKMVe8vJvoi3w5X5jVIYJoM4nqnVM7 eD7+9XtwgkTZaKdI2ktkABOkLQeAQrxvPzYxjUGJBfXimRv0qEnLimiqivcIqkNhPL yUcpVyTbKG9ZA== Received: by letrec.thunk.org (Postfix, from userid 15806) id B4E848C02FA; Fri, 10 Nov 2023 12:08:35 -0500 (EST) Date: Fri, 10 Nov 2023 12:08:35 -0500 From: "Theodore Ts'o" To: Aleksandr Nogikh Cc: Thomas Gleixner , syzbot , adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [ext4?] general protection fault in hrtimer_nanosleep Message-ID: References: <000000000000cfd180060910a687@google.com> <875y2lmxys.ffs@tglx> <87r0l8kv1s.ffs@tglx> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Nov 09, 2023 at 09:00:18PM -0800, Aleksandr Nogikh wrote: > > The reproducer does work on the attached disk image, but definitely > not very often. I've just run it 10 times or so and got interleaved > BUG/KFENCE bug reports like this (twice): > https://pastebin.com/W0TkRsnw > > These seem to be related to ext4 rather than hrtimers though. So what would be nice is if there was a way to ask the syzkaller tester to use a different config or to change the reproducer somehow --- for example, is it *really* necessary to twiddle the bluetooth subsystem, as demonstrated by the spew in the console? I've certainly spent hours cutting down the reproducer to a simple C program which is readable by humans, which makes it *clear* the syzbot minimizer doesn't do a good job. Why should a time-limited maintainer spend hours trying to cut down the reproducer, when a robot should be able to do that for us? And when often it doesn't reproduce on anything via syzbot test, but not when run using KVM, this is why we need to have a simple way of trigger a test where things are as close as possible to whatever syzbot is using. Cheers, - Ted