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Wed, 13 Dec 2023 07:31:46 -0800 (PST) MIME-Version: 1.0 References: <20231128075532.110251-1-haibo.li@mediatek.com> <20231128172238.f80ed8dd74ab2a13eba33091@linux-foundation.org> In-Reply-To: From: Andrey Konovalov Date: Wed, 13 Dec 2023 16:31:35 +0100 Message-ID: Subject: Re: [PATCH] fix comparison of unsigned expression < 0 To: Dan Carpenter Cc: "Liu, Yujie" , Andrew Morton , kernel test robot , Haibo Li , linux-kernel@vger.kernel.org, Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Vincenzo Frascino , Matthias Brugger , AngeloGioacchino Del Regno , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, xiaoming.yu@mediatek.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 3F5761A001C X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: ujum5fb3je1pdyabb6jjaw4msxeau764 X-HE-Tag: 1702481508-575155 X-HE-Meta: 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 jsuL/KKW 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000007, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Dec 4, 2023 at 5:12=E2=80=AFAM Dan Carpenter wrote: > > > But I actually don't think we need to fix anything here. > > > > This issue looks quite close to a similar comparison with 0 issue > > Linus shared his opinion on here: > > > > https://lore.kernel.org/all/Pine.LNX.4.58.0411230958260.20993@ppc970.os= dl.org/ > > > > I don't know if the common consensus with the regard to issues like > > that changed since then. But if not, perhaps we can treat this kernel > > test robot report as a false positive. > > I would say that the consensus has changed somewhere around 2015 or > so. Unsigned comparisons to zero used to be one of the most common > types of bugs in new code but now almost all subsystems have turned on > the GCC warning for this. > > However, this is a Smatch warning and I agree with Linus on this. For > example, Smatch doesn't complain about the example code the Linus > mentioned. > > if (a < 0 || a > X) > > And in this case, it's a one liner fix for me to add KASAN_SHADOW_OFFSET > as an allowed macro and silence the warning. Hi Dan, If this sounds like a good idea to you, please add an exception. >From the KASAN side, I think adding an exception for this case makes sense. Thank you!