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Wed, 26 May 2021 09:49:36 -0700 (PDT) Received: from ziepe.ca ([206.223.160.26]) by smtp.gmail.com with ESMTPSA id d11sm1912764qkj.24.2021.05.26.09.49.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 May 2021 09:49:35 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1llwis-00FEKy-GU; Wed, 26 May 2021 13:49:34 -0300 Date: Wed, 26 May 2021 13:49:34 -0300 From: Jason Gunthorpe To: Colin King Cc: =?utf-8?B?SsOpcsO0bWU=?= Glisse , Alistair Popple , Ralph Campbell , Stephen Rothwell , Andrew Morton , linux-mm@kvack.org, kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH][next] mm: selftests: fix potential integer overflow on shift of a int Message-ID: <20210526164934.GD1096940@ziepe.ca> References: <20210526150947.3751728-1-colin.king@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210526150947.3751728-1-colin.king@canonical.com> Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=ziepe.ca header.s=google header.b=EDhzTJ5P; dmarc=none; spf=pass (imf01.hostedemail.com: domain of jgg@ziepe.ca designates 209.85.222.179 as permitted sender) smtp.mailfrom=jgg@ziepe.ca X-Stat-Signature: jyhz3nigg857cg3b5u6fibh4rk4tmsf5 X-Rspamd-Queue-Id: D82B25001650 X-Rspamd-Server: rspam02 X-HE-Tag: 1622047769-813374 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, May 26, 2021 at 04:09:47PM +0100, Colin King wrote: > From: Colin Ian King > > The left shift of the int mapped is evaluated using 32 bit arithmetic > and then assigned to an unsigned long. In the case where mapped is > 0x80000 when PAGE_SHIFT is 12 will lead to the upper bits being > sign extended in the unsigned long. Larger values can lead to an > int overflow. Avoid this by casting mapped to unsigned long before > shifting. > > Addresses-Coverity: ("Uninitentional integer overflow") > Fixes: 8b2a105c3794 ("mm: selftests for exclusive device memory") > Signed-off-by: Colin Ian King > lib/test_hmm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/lib/test_hmm.c b/lib/test_hmm.c > index 74d69f87691e..b54657701b3a 100644 > +++ b/lib/test_hmm.c > @@ -749,7 +749,7 @@ static int dmirror_exclusive(struct dmirror *dmirror, > } > } > > - if (addr + (mapped << PAGE_SHIFT) < next) { > + if (addr + ((unsigned int)mapped << PAGE_SHIFT) < next) { Just fix the type for mapped. It started out as an unsigned long in dmirror_atomic_map() and wrongly became an int here Jason