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([2001:b07:6468:f312:63a7:c72e:ea0e:6045]) by smtp.gmail.com with ESMTPSA id x15sm11430781wro.66.2021.02.08.03.40.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 08 Feb 2021 03:40:35 -0800 (PST) Subject: Re: [PATCH] scsi: mptsas: dequeue request object in case of an error (CVE-2021-3392) To: P J P References: <20210202132103.1096654-1-ppandit@redhat.com> From: Paolo Bonzini Message-ID: <5d72e28a-c6fc-6cb3-d491-84d7dfed01b8@redhat.com> Date: Mon, 8 Feb 2021 12:40:34 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20210202132103.1096654-1-ppandit@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pbonzini@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.57, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.265, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, 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: Fam Zheng , Cheolwoo Myung , QEMU Developers , Prasad J Pandit Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 02/02/21 14:21, P J P wrote: > From: Prasad J Pandit > > While processing SCSI i/o requests in mptsas_process_scsi_io_request(), > the Megaraid emulator appends new MPTSASRequest object 'req' to > the 's->pending' queue. In case of an error, this same object gets > dequeued in mptsas_free_request() only if SCSIRequest object > 'req->sreq' is initialised. This may lead to a use-after-free issue. > Unconditionally dequeue 'req' object from 's->pending' to avoid it. > > Fixes: CVE-2021-3392 > Buglink: https://bugs.launchpad.net/qemu/+bug/1914236 > Reported-by: Cheolwoo Myung > Signed-off-by: Prasad J Pandit > --- > hw/scsi/mptsas.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/hw/scsi/mptsas.c b/hw/scsi/mptsas.c > index f86616544b..adff5b0bf2 100644 > --- a/hw/scsi/mptsas.c > +++ b/hw/scsi/mptsas.c > @@ -257,8 +257,8 @@ static void mptsas_free_request(MPTSASRequest *req) > req->sreq->hba_private = NULL; > scsi_req_unref(req->sreq); > req->sreq = NULL; > - QTAILQ_REMOVE(&s->pending, req, next); > } > + QTAILQ_REMOVE(&s->pending, req, next); > qemu_sglist_destroy(&req->qsg); > g_free(req); > } > s->pending is not used for anything, it can just be removed. Paolo