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Tue, 09 Feb 2021 09:19:36 +0000 Received: from abhmp0003.oracle.com (abhmp0003.oracle.com [141.146.116.9]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 1199JXkl007635; Tue, 9 Feb 2021 09:19:34 GMT Received: from kadam (/102.36.221.92) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 09 Feb 2021 01:19:33 -0800 Date: Tue, 9 Feb 2021 12:19:23 +0300 From: Dan Carpenter To: Will Deacon Subject: Re: [PATCH][next] iommu/mediatek: Fix unsigned domid comparison with less than zero Message-ID: <20210209091923.GO2696@kadam> References: <20210203135936.23016-1-colin.king@canonical.com> <20210204092558.GA20244@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210204092558.GA20244@willie-the-truck> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-IMR: 1 X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9889 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 bulkscore=0 adultscore=0 mlxlogscore=999 phishscore=0 spamscore=0 suspectscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102090045 X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9889 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 spamscore=0 lowpriorityscore=0 phishscore=0 adultscore=0 impostorscore=0 suspectscore=0 mlxscore=0 clxscore=1011 mlxlogscore=999 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102090045 Cc: Anan sun , kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org, Chao Hao , iommu@lists.linux-foundation.org, linux-mediatek@lists.infradead.org, linux-arm-kernel@lists.infradead.org, Matthias Brugger , Colin King X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Thu, Feb 04, 2021 at 09:25:58AM +0000, Will Deacon wrote: > On Wed, Feb 03, 2021 at 01:59:36PM +0000, Colin King wrote: > > From: Colin Ian King > > > > Currently the check for domid < 0 is always false because domid > > is unsigned. Fix this by making it signed. > > > > Addresses-CoverityL ("Unsigned comparison against 0") > > Typo here ('L' instead of ':') > > > Fixes: ab1d5281a62b ("iommu/mediatek: Add iova reserved function") > > Signed-off-by: Colin Ian King > > --- > > drivers/iommu/mtk_iommu.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c > > index 0ad14a7604b1..823d719945b2 100644 > > --- a/drivers/iommu/mtk_iommu.c > > +++ b/drivers/iommu/mtk_iommu.c > > @@ -640,7 +640,7 @@ static void mtk_iommu_get_resv_regions(struct device *dev, > > struct list_head *head) > > { > > struct mtk_iommu_data *data = dev_iommu_priv_get(dev); > > - unsigned int domid = mtk_iommu_get_domain_id(dev, data->plat_data), i; > > + int domid = mtk_iommu_get_domain_id(dev, data->plat_data), i; > > Not sure if it's intentional, but this also makes 'i' signed. It probably > should remain 'unsigned' to match 'iova_region_nr' in > 'struct mtk_iommu_plat_data'. iova_region_nr is either 1 or 5 so unsigned doesn't matter. I once almost introduced a bug where the iterator was supposed to be size_t. I fixed a bug by making it signed but I ended up introducing a new bug. But generally that's pretty rare. The more common case is that making iterators unsigned introduces bugs. It's better to default to "int i;" and if more complicated types are required that should stand out. "size_t pg_idx;" or whatever. regards, dan carpenter _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu