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Wed, 5 Aug 2020 13:39:54 +0000 (UTC) Date: Wed, 5 Aug 2020 15:39:53 +0200 From: Kevin Wolf To: Tuguoyi Subject: Re: [PATCH] qcow2-cluster: Fix integer left shift error in qcow2_alloc_cluster_link_l2() Message-ID: <20200805133953.GC4679@linux.fritz.box> References: <81ba90fe0c014f269621c283269b42ad@h3c.com> MIME-Version: 1.0 In-Reply-To: <81ba90fe0c014f269621c283269b42ad@h3c.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=205.139.110.61; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/05 04:10:11 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peter.maydell@linaro.org, Chengchiwen , "qemu-block@nongnu.org" , "qemu-devel@nongnu.org" , "mreitz@redhat.com" , Gaoliang , Wangyong Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 05.08.2020 um 11:22 hat Tuguoyi geschrieben: > When calculating the offset, the result of left shift operation will be promoted > to type int64 automatically because the left operand of + operator is uint64_t. > but the result after integer promotion may be produce an error value for us and > trigger the following asserting error. > > For example, consider i=0x2000, cluster_bits=18, the result of left shift > operation will be 0x80000000. Cause argument i is of signed integer type, > the result is automatically promoted to 0xffffffff80000000 which is not > we expected > > The way to trigger the assertion error: > qemu-img create -f qcow2 -o preallocation=full,cluster_size=256k tmpdisk 10G > > This patch fix it by casting @i to uint64_t before doing left shift operation > > Signed-off-by: Guoyi Tu Reviewed-by: Kevin Wolf