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Tue, 9 Feb 2021 11:57:32 +0100 Received: from SRVEX01-SZ.bfs.intern ([fe80::7d2d:f9cb:2761:d24a]) by SRVEX01-SZ.bfs.intern ([fe80::7d2d:f9cb:2761:d24a%13]) with mapi id 15.01.2176.002; Tue, 9 Feb 2021 11:57:32 +0100 From: Walter Harms To: Dan Carpenter , Will Deacon CC: Colin King , Joerg Roedel , Matthias Brugger , Anan sun , Yong Wu , Chao Hao , Tomasz Figa , "iommu@lists.linux-foundation.org" , "linux-arm-kernel@lists.infradead.org" , "linux-mediatek@lists.infradead.org" , "kernel-janitors@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: AW: [PATCH][next] iommu/mediatek: Fix unsigned domid comparison with less than zero Thread-Topic: [PATCH][next] iommu/mediatek: Fix unsigned domid comparison with less than zero Thread-Index: AQHW+jVw6vQF7iLM7kGMzk6JKLJ0oqpHqk8AgAfZ0YCAACsEgg== Date: Tue, 9 Feb 2021 10:57:32 +0000 Message-ID: References: <20210203135936.23016-1-colin.king@canonical.com> <20210204092558.GA20244@willie-the-truck>,<20210209091923.GO2696@kadam> In-Reply-To: <20210209091923.GO2696@kadam> Accept-Language: de-DE, en-US Content-Language: de-DE X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.137.16.39] x-tm-as-product-ver: SMEX-14.0.0.3080-8.6.1012-25962.007 x-tm-as-result: No-10--7.431600-5.000000 x-tmase-matchedrid: qqoVTVjx6YDRubRCcrbc5grcxrzwsv5u3dCmvEa6IiHgYNP0+4v1nizy bVqWyY2NjrJzIoPQuMw+otRoIV3vSHVgBjkrax/H52zh+cq/0JuQBbTqDF++CmOMyb1Ixq8VUDG dbyXu/ma30GP8pin5GSKkzMT7+4ooN9rojbjxBkzXA3LnlKuVLMqFE6gRdROb+nlefiwGml8hlG 9iTcYtaqNIXC+Evb2D1qIE4CfpJ4zBm5Pnp+5TT/SG/+sPtZVkJih/yo+OvlXk6Qbi+9i6D0MmJ 6dGmSIy2JDeaNwtlNBVVkf0bJfBjyxppiUy9o4cGjzBgnFZvQ4vV5f7P0HVDETqq9Xa45y5XJvT MgAKYypb2hQcAFTn3WnsfYyMrTTf6Ne/nacGH0HM0ihsfYPMYdFTR6mnbN4LvGAx/1ATZ5sJetz 2R9zIsefqkkwronku/Sj/WnCM/LO/WXZS/HqJ2gtuKBGekqUpbGVEmIfjf3vt19sHZWTQhkfEDy E6wbBxQsEUiq7rfWGPfhLI9kH4wx7PLpUeWnT+ x-tm-as-user-approved-sender: No x-tm-as-user-blocked-sender: No x-tmase-result: 10--7.431600-5.000000 x-tmase-version: SMEX-14.0.0.3080-8.6.1012-25962.007 x-tm-snts-smtp: 8C502E7B3B6532B6AC707D8C4AE56DFF89CE4B2F07035BEC56FE6C2324B7857A2000:9 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-Spamd-Result: default: False [0.82 / 7.00]; ARC_NA(0.00)[]; TO_DN_EQ_ADDR_SOME(0.00)[]; HAS_XOIP(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; TAGGED_RCPT(0.00)[]; MIME_GOOD(-0.10)[text/plain]; MID_RHS_MATCH_FROM(0.00)[]; DKIM_SIGNED(0.00)[bfs.de:s=dkim201901]; BAYES_HAM(-0.68)[83.00%]; RCPT_COUNT_TWELVE(0.00)[14]; NEURAL_HAM(-0.00)[-1.000]; RCVD_NO_TLS_LAST(0.10)[]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; FREEMAIL_CC(0.00)[canonical.com,8bytes.org,gmail.com,mediatek.com,chromium.org,lists.linux-foundation.org,lists.infradead.org,vger.kernel.org]; RCVD_COUNT_TWO(0.00)[2]; SUSPICIOUS_RECIPS(1.50)[] Authentication-Results: mx01-sz.bfs.de; none Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I second that ... Having i unsigned violates the rule of "least surprise". If you need it unsigned make it clearly visible, also adding a simple comment may help. jm2c, wh ________________________________________ Von: Dan Carpenter Gesendet: Dienstag, 9. Februar 2021 10:19:23 An: Will Deacon Cc: Colin King; Joerg Roedel; Matthias Brugger; Anan sun; Yong Wu; Chao Hao= ; Tomasz Figa; iommu@lists.linux-foundation.org; linux-arm-kernel@lists.inf= radead.org; linux-mediatek@lists.infradead.org; kernel-janitors@vger.kernel= .org; linux-kernel@vger.kernel.org Betreff: Re: [PATCH][next] iommu/mediatek: Fix unsigned domid comparison wi= th less than zero 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 devic= e *dev, > > struct list_head *head) > > { > > struct mtk_iommu_data *data =3D dev_iommu_priv_get(dev); > > - unsigned int domid =3D mtk_iommu_get_domain_id(dev, data->plat_data= ), i; > > + int domid =3D 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