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 9F8E533C9 for ; Sun, 11 Aug 2024 01:30:36 +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=1723339839; cv=none; b=K25WnS9pvRkzMlevHjfX773XRa8xG4ereUUYuGQfVXGEiwWk+4kYceb1X3SGud6NsSCmvZNOcF4rnO4wmbLzEdPFxv1rkraX6EkUT3eUcfdO1HZF1ka2ayzMbNW9daNNBnsnXHklqkwQzv/QJtmVp4M8Ss9t9wnpHWGWh3NgmN0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723339839; c=relaxed/simple; bh=rwxTacSsqq5yZxZCCk9LwOklyI/5rUVH+qneGn1PoCg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=mRUYZ7z3yWPROBegvMgYVLLJlJ5O2rLGS86cdhpZfXQg9qhk56V2di1uQZVcZcleRNTKlBQigALemSVPH2UVfwA3TSzB/78K9HpfXRt2NuIDHMI4UbhdoKy0dTMm7t/OQd86y30cAqw+5q/7FWrfBlbVbsOYqijFe7ED7jAjGWo= 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=KCbyT7DU; 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="KCbyT7DU" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1723339835; 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=J14+5lRnQsP0ngrAC8bOeli66OZFssq5LR5RO6HiXiI=; b=KCbyT7DUfbCRNtLayjXjdgdyE8wyAGuEuOkhA6XQi4Df86gaILIjCR8iN7SMiJLsIglSKj vnmW+GDksbEeQx0ZFUYq/3keSixTVKd7N9V6Iv27kddZJ/reQA/sClzLJkCdz0kVksqVan W4m8FSX77G0gHuRFlvsNM4OhuM3zeW4= 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-394-x5KfbBM_MUqtZUqJXPWI2A-1; Sat, 10 Aug 2024 21:30:30 -0400 X-MC-Unique: x5KfbBM_MUqtZUqJXPWI2A-1 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (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 DEFA31955F43; Sun, 11 Aug 2024 01:30:28 +0000 (UTC) Received: from [10.22.32.2] (unknown [10.22.32.2]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id EC974197703E; Sun, 11 Aug 2024 01:30:26 +0000 (UTC) Message-ID: Date: Sat, 10 Aug 2024 21:30:25 -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: Herbert Xu Cc: steffen.klassert@secunet.com, daniel.m.jordan@oracle.com, akpm@linux-foundation.org, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org References: Content-Language: en-US From: Waiman Long In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 On 8/10/24 00:05, Herbert Xu wrote: > Waiman Long wrote: >> 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().` >> + */ >> + if (!ps.chunk_size) >> + ps.chunk_size = 1U; > Perhaps change the first ps.chunk_size assignment to use DIV_ROUND_UP > instead? I think DIV_ROUND_UP() will exactly the same problem that if chunk_size is 0, you still got a 0 result. round_up() only if the 2nd argument is a power of 2 while with DIV_ROUND_UP(), the second argument can be any number except 0. Cheers, Longman