From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 81B39C43334 for ; Tue, 28 Jun 2022 06:55:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343588AbiF1Gzl (ORCPT ); Tue, 28 Jun 2022 02:55:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34808 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229548AbiF1Gzi (ORCPT ); Tue, 28 Jun 2022 02:55:38 -0400 Received: from madras.collabora.co.uk (madras.collabora.co.uk [46.235.227.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 01B7E22BCE for ; Mon, 27 Jun 2022 23:55:37 -0700 (PDT) Received: from localhost (unknown [IPv6:2a01:e0a:2c:6930:5cf4:84a1:2763:fe0d]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bbrezillon) by madras.collabora.co.uk (Postfix) with ESMTPSA id 271F46601856; Tue, 28 Jun 2022 07:55:36 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1656399336; bh=CQRz8B+bkCZiBSEzDEK0Y9ZfKFUVGt+3EPrz6C/F4nY=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=O+RMMaj3oBnqHjdgpSOaqa6f+tPOSOEwu1KRsgBClppDzGAMEKwdrouboQx1xoaHj Qt+dZ4yKEZJuqujtaMAVddWovXt20NWHKAJk4g6wgUKdk0GGQqIN4EKsHbsn7uta/r vAgkHTcgjTso4dwIzGHXoC32yWxpoz/MdOj40AkpVK02QSQU+uEcgq98mEviu9pxEB e5MJWzaTT0AghPFLD1KGjSold/SE/VkhEkiqPn+zB3S6HZSDTNSZhNjQAro6lZUZpM wdvT+GFW980Thc3wInmUjDug9aPLc1alUgWp+QabbGjpZlvOi17SI8wWq2OmabedMG 97P8/KZ0wvB2w== Date: Tue, 28 Jun 2022 08:55:33 +0200 From: Boris Brezillon To: Yu Liao Cc: , , , , , Subject: Re: [PATCH] drm/vc4: fix dereference before NULL check Message-ID: <20220628085533.7b7885fb@collabora.com> In-Reply-To: <20220628063657.3169049-1-liaoyu15@huawei.com> References: <20220628063657.3169049-1-liaoyu15@huawei.com> Organization: Collabora X-Mailer: Claws Mail 4.1.0 (GTK 3.24.34; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 28 Jun 2022 14:36:57 +0800 Yu Liao wrote: > The "perfmon" pointer is equal to the return value of idr_find > which may be NULL, access by vc4_perfmon_get before checking if > it was NULL. Fix this by dereferencing "perfmon" after "perfmon" > has been null checked. > > Addresses-Coverity: ("Dereference before null check") > Fixes: 65101d8c9108 ("drm/vc4: Expose performance counters to userspace") > Signed-off-by: Yu Liao Reviewed-by: Boris Brezillon > --- > drivers/gpu/drm/vc4/vc4_perfmon.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/vc4/vc4_perfmon.c b/drivers/gpu/drm/vc4/vc4_perfmon.c > index c7f5adb6bcf8..ca969b8c7dde 100644 > --- a/drivers/gpu/drm/vc4/vc4_perfmon.c > +++ b/drivers/gpu/drm/vc4/vc4_perfmon.c > @@ -17,13 +17,17 @@ > > void vc4_perfmon_get(struct vc4_perfmon *perfmon) > { > - struct vc4_dev *vc4 = perfmon->dev; > + struct vc4_dev *vc4; > + > + if (!perfmon) > + return; > + > + vc4 = perfmon->dev; > > if (WARN_ON_ONCE(vc4->is_vc5)) > return; > > - if (perfmon) > - refcount_inc(&perfmon->refcnt); > + refcount_inc(&perfmon->refcnt); > } > > void vc4_perfmon_put(struct vc4_perfmon *perfmon)