From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 D74D0EAC5 for ; Sun, 11 Aug 2024 03:33:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723347195; cv=none; b=ne+kzzp+AeRM/OvfmQSSP6GGHGLnN+5swzpnuaoXHIAfwpq+xuvnEQvXQCM6LEK9i8jzkuuHBvIEd/xvpKuYUArPH9v9jyqTWTpsNqSSw4NoueNCnZ6M6Q6EkJE8EWFTBzXj93svSANuIMMgysTINLUP/jZKXEGvVRFXM591X0M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723347195; c=relaxed/simple; bh=RXSGsS5nRAU3Mxx6h5fdvjzbqyKm0z85Q4yvcUy6f1E=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=A4UaaUJSDnop8BbxVcNFVntkk2m8g8FvVhBnSPkXBM6JMLZ7dBfQJma4DJndNXWhBKqKnhkSFNA1qORWzEqJf/a3040FjNZqDYg9n4j0u5lbM3gm3AyXAXBFil03AT9J9bE0hvEeHoJ9MYtLAad4vlDABJcOWf2hFo76bvsA5Do= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=LtZ7EYxh; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="LtZ7EYxh" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1723347192; h=from:from: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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=uWNClqGeRNafoYy78wwBYXSlMYcDTGBQ8Qtwon24Sxs=; b=LtZ7EYxh5EDQKxnUDvyUTqO90AnjskrtUTs4xhLtFjrX3Tqv/Q+qgVOpCcikv1cxZYjg1T VOXxDPR0/jUPBBKtPYs4pnavVYMU3HFYn15Y0G3+PisHiRQ2tXUAS6cve8Pp2iGYZcOB8a M+H81oUqO1Y4QjjFrjz+OQGQq8Mr9LI= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-76-uy0K6KpzOrmGiyWptNtyeg-1; Sat, 10 Aug 2024 23:33:08 -0400 X-MC-Unique: uy0K6KpzOrmGiyWptNtyeg-1 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A028A1955F43; Sun, 11 Aug 2024 03:33:06 +0000 (UTC) Received: from [10.2.16.6] (unknown [10.2.16.6]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 0226A19560A3; Sun, 11 Aug 2024 03:33:04 +0000 (UTC) Message-ID: <70e28278-d9cf-4158-b296-cabe7786e4a7@redhat.com> Date: Sat, 10 Aug 2024 23:33:03 -0400 Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] padata: Fix possible divide-by-0 panic in padata_mt_helper() To: Kamlesh Gurudasani , Steffen Klassert , Daniel Jordan , Andrew Morton Cc: linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org References: <20240806174647.1050398-1-longman@redhat.com> <87jzgonug5.fsf@kamlesh.i-did-not-set--mail-host-address--so-tickle-me> Content-Language: en-US From: Waiman Long In-Reply-To: <87jzgonug5.fsf@kamlesh.i-did-not-set--mail-host-address--so-tickle-me> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 On 8/10/24 13:44, Kamlesh Gurudasani wrote: > Waiman Long writes: > >> We are hit with a not easily reproducible divide-by-0 panic in padata.c >> at bootup time. >> >> [ 10.017908] Oops: divide error: 0000 1 PREEMPT SMP NOPTI >> [ 10.017908] CPU: 26 PID: 2627 Comm: kworker/u1666:1 Not tainted 6.10.0-15.el10.x86_64 #1 >> [ 10.017908] Hardware name: Lenovo ThinkSystem SR950 [7X12CTO1WW]/[7X12CTO1WW], BIOS [PSE140J-2.30] 07/20/2021 >> [ 10.017908] Workqueue: events_unbound padata_mt_helper >> [ 10.017908] RIP: 0010:padata_mt_helper+0x39/0xb0 >> : >> [ 10.017963] Call Trace: >> [ 10.017968] >> [ 10.018004] ? padata_mt_helper+0x39/0xb0 >> [ 10.018084] process_one_work+0x174/0x330 >> [ 10.018093] worker_thread+0x266/0x3a0 >> [ 10.018111] kthread+0xcf/0x100 >> [ 10.018124] ret_from_fork+0x31/0x50 >> [ 10.018138] ret_from_fork_asm+0x1a/0x30 >> [ 10.018147] >> >> Looking at the padata_mt_helper() function, the only way a divide-by-0 >> panic can happen is when ps->chunk_size is 0. The way that chunk_size is >> initialized in padata_do_multithreaded(), chunk_size can be 0 when the >> min_chunk in the passed-in padata_mt_job structure is 0. >> >> Fix this divide-by-0 panic by making sure that chunk_size will be at >> least 1 no matter what the input parameters are. >> >> Fixes: 004ed42638f4 ("padata: add basic support for multithreaded jobs") >> Signed-off-by: Waiman Long >> --- >> kernel/padata.c | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> diff --git a/kernel/padata.c b/kernel/padata.c >> index 53f4bc912712..0fa6c2895460 100644 >> --- a/kernel/padata.c >> +++ b/kernel/padata.c >> @@ -517,6 +517,13 @@ void __init padata_do_multithreaded(struct padata_mt_job *job) >> ps.chunk_size = max(ps.chunk_size, job->min_chunk); >> ps.chunk_size = roundup(ps.chunk_size, job->align); >> >> + /* >> + * chunk_size can be 0 if the caller sets min_chunk to 0. So force it >> + * to at least 1 to prevent divide-by-0 panic in padata_mt_helper().` >> + */ > Thanks for the patch and detailed comment. >> + if (!ps.chunk_size) >> + ps.chunk_size = 1U; >> + > could it be > ps.chunk_size = max(ps.chunk_size, 1U); > > or can be merged with earlier max() > ps.chunk_size = max(ps.chunk_size, max(job->min_chunk, 1U)); > ps.chunk_size = roundup(ps.chunk_size, job->align); > > sits well with how entire file is written and compiler is optimizing > them to same level. I had actually thought about doing that as an alternative. I used the current patch to avoid putting too many max() calls there. I can go this route if you guys prefer this. Cheers, Longman