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Thu, 11 Jun 2020 12:56:11 +0000 (UTC) Subject: Re: [PATCH v2 3/8] s390/sclp: rework sclp boundary and length checks To: Collin Walling , qemu-devel@nongnu.org, qemu-s390x@nongnu.org References: <20200515222032.18838-1-walling@linux.ibm.com> <20200515222032.18838-4-walling@linux.ibm.com> From: Thomas Huth Openpgp: preference=signencrypt Message-ID: <2db81475-f4cd-448f-561a-fa545db1ae9d@redhat.com> Date: Thu, 11 Jun 2020 14:56:10 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200515222032.18838-4-walling@linux.ibm.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=207.211.31.120; envelope-from=thuth@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/11 08:37:10 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 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_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN 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: frankja@linux.ibm.com, david@redhat.com, cohuck@redhat.com, pasic@linux.ibm.com, borntraeger@de.ibm.com, mst@redhat.com, svens@linux.ibm.com, pbonzini@redhat.com, mihajlov@linux.ibm.com, rth@twiddle.net Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 16/05/2020 00.20, Collin Walling wrote: > Rework the SCLP boundary check to account for different SCLP commands > (eventually) allowing different boundary sizes. > > Move the length check code into a separate function, and introduce a > new function to determine the length of the read SCP data (i.e. the size > from the start of the struct to where the CPU entries should begin). > > Signed-off-by: Collin Walling > --- > hw/s390x/sclp.c | 57 ++++++++++++++++++++++++++++++++++++++++++------- > 1 file changed, 49 insertions(+), 8 deletions(-) > > diff --git a/hw/s390x/sclp.c b/hw/s390x/sclp.c > index 2bd618515e..987699e3c4 100644 > --- a/hw/s390x/sclp.c > +++ b/hw/s390x/sclp.c > @@ -49,6 +49,34 @@ static inline bool sclp_command_code_valid(uint32_t code) > return false; > } > > +static bool sccb_has_valid_boundary(uint64_t sccb_addr, uint32_t code, > + SCCBHeader *header) > +{ > + uint64_t current_len = sccb_addr + be16_to_cpu(header->length); > + uint64_t allowed_len = (sccb_addr & PAGE_MASK) + PAGE_SIZE; > + > + switch (code & SCLP_CMD_CODE_MASK) { > + default: > + if (current_len <= allowed_len) { > + return true; > + } > + } > + header->response_code = cpu_to_be16(SCLP_RC_SCCB_BOUNDARY_VIOLATION); > + return false; > +} > + > +/* Calculates sufficient SCCB length to store a full Read SCP/CPU response */ > +static bool sccb_has_sufficient_len(SCCB *sccb, int num_cpus, int data_len) > +{ > + int required_len = data_len + num_cpus * sizeof(CPUEntry); > + > + if (be16_to_cpu(sccb->h.length) < required_len) { > + sccb->h.response_code = cpu_to_be16(SCLP_RC_INSUFFICIENT_SCCB_LENGTH); > + return false; > + } > + return true; > +} > + > static void prepare_cpu_entries(MachineState *ms, CPUEntry *entry, int *count) > { > uint8_t features[SCCB_CPU_FEATURE_LEN] = { 0 }; > @@ -66,6 +94,16 @@ static void prepare_cpu_entries(MachineState *ms, CPUEntry *entry, int *count) > } > } > > +/* > + * The data length denotes the start of the struct to where the first > + * CPU entry is to be allocated. This value also denotes the offset_cpu > + * field. > + */ > +static int get_read_scp_info_data_len(void) > +{ > + return offsetof(ReadInfo, entries); > +} > + > /* Provide information about the configuration, CPUs and storage */ > static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb) > { > @@ -74,16 +112,16 @@ static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb) > int cpu_count; > int rnsize, rnmax; > IplParameterBlock *ipib = s390_ipl_get_iplb(); > + int data_len = get_read_scp_info_data_len(); > > - if (be16_to_cpu(sccb->h.length) < (sizeof(ReadInfo) + cpu_count * sizeof(CPUEntry))) { > - sccb->h.response_code = cpu_to_be16(SCLP_RC_INSUFFICIENT_SCCB_LENGTH); > + if (!sccb_has_sufficient_len(sccb, machine->possible_cpus->len, data_len)) { > return; > } > > /* CPU information */ > prepare_cpu_entries(machine, read_info->entries, &cpu_count); > read_info->entries_cpu = cpu_to_be16(cpu_count); > - read_info->offset_cpu = cpu_to_be16(offsetof(ReadInfo, entries)); > + read_info->offset_cpu = cpu_to_be16(data_len); > read_info->highest_cpu = cpu_to_be16(machine->smp.max_cpus - 1); > > read_info->ibc_val = cpu_to_be32(s390_get_ibc_val()); > @@ -132,16 +170,16 @@ static void sclp_read_cpu_info(SCLPDevice *sclp, SCCB *sccb) > { > MachineState *machine = MACHINE(qdev_get_machine()); > ReadCpuInfo *cpu_info = (ReadCpuInfo *) sccb; > + int data_len = offsetof(ReadCpuInfo, entries); Is there a reason for not using get_read_scp_info_data_len() here? Thomas