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Mon, 13 Jul 2020 15:50:58 +0000 (UTC) Date: Mon, 13 Jul 2020 17:50:53 +0200 From: Igor Mammedov To: Markus Armbruster Subject: Re: [PATCH v2 20/25] x86: Fix x86_cpu_new() error API violations Message-ID: <20200713175053.2dd20026@redhat.com> In-Reply-To: <875zbeugvl.fsf@dusky.pond.sub.org> References: <20200624083737.3086768-1-armbru@redhat.com> <20200624083737.3086768-21-armbru@redhat.com> <20200624161703.153c7905@redhat.com> <875zbeugvl.fsf@dusky.pond.sub.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=207.211.31.81; envelope-from=imammedo@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/13 02:19:41 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=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: Paolo Bonzini , Richard Henderson , qemu-devel@nongnu.org, Eduardo Habkost Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, 26 Jun 2020 14:54:38 +0200 Markus Armbruster wrote: > Igor Mammedov writes: > > > On Wed, 24 Jun 2020 10:37:32 +0200 > > Markus Armbruster wrote: > > > >> The Error ** argument must be NULL, &error_abort, &error_fatal, or a > >> pointer to a variable containing NULL. Passing an argument of the > >> latter kind twice without clearing it in between is wrong: if the > >> first call sets an error, it no longer points to NULL for the second > >> call. > >> > >> x86_cpu_new() is wrong that way: it passes &local_err to > >> object_property_set_uint() without checking it, and then to > >> qdev_realize(). Harmless, because the former can't actually fail > >> here. > >> > >> Fix by checking for failure right away. While there, replace > >> qdev_realize(); object_unref() by qdev_realize_and_unref(). > >> > >> Cc: Paolo Bonzini > >> Cc: Richard Henderson > >> Cc: Eduardo Habkost > >> Signed-off-by: Markus Armbruster > >> --- > >> hw/i386/x86.c | 12 +++--------- > >> 1 file changed, 3 insertions(+), 9 deletions(-) > >> > >> diff --git a/hw/i386/x86.c b/hw/i386/x86.c > >> index 34229b45c7..3a7029e6db 100644 > >> --- a/hw/i386/x86.c > >> +++ b/hw/i386/x86.c > >> @@ -118,16 +118,10 @@ uint32_t x86_cpu_apic_id_from_index(X86MachineState *x86ms, > >> > >> void x86_cpu_new(X86MachineState *x86ms, int64_t apic_id, Error **errp) > >> { > >> - Object *cpu = NULL; > >> - Error *local_err = NULL; > >> + Object *cpu = object_new(MACHINE(x86ms)->cpu_type); > >> > >> - cpu = object_new(MACHINE(x86ms)->cpu_type); > >> - > >> - object_property_set_uint(cpu, apic_id, "apic-id", &local_err); > >> - qdev_realize(DEVICE(cpu), NULL, &local_err); > >> - > >> - object_unref(cpu); > >> - error_propagate(errp, local_err); > >> + object_property_set_uint(cpu, apic_id, "apic-id", &error_abort); > > it may fail here if user specified wrong cpu flags, but there is nothing we can do to fix it. > > Really? > > object_property_set_uint() fails when property "apic-id" doesn't exist, > has no ->set() method, or its ->set() fails. > > Property "apic-id" is defined in x86_cpu_properties[] as > > DEFINE_PROP_UINT32("apic-id", X86CPU, apic_id, UNASSIGNED_APIC_ID), > > This means "apic-id" exists, and its ->set() is set_uint32(). That > leaves only set_uint32() as possible source of failure. > > It fails when > > * the device is already realized: programming error > > * the value to be stored is not an integer: object_property_set_uint() > makes it one, can't fail > > * the value is not representable as uint32_t: @api_id is declared as > int64_t, but: > > - pc_hot_add_cpu() passes x86_cpu_apic_id_from_index(), which is > uint32_t, converted to int64_t. Can't fail. > > - x86_cpus_init() passes possible_cpus->cpus[i].arch_id, which is > uint64_t. Is this the "if user specified wrong cpu flags" case? looking more on it, object_property_set_uint() can't really fail > Aside: should the integer types be cleaned up? apic_id is x86 specific subset of .arch_id. The later is used by other targets which may need larger than 32bit integer (if I recall correctly virt-arm uses 64bit id). > To assess the bug's impact, we need to know when the other call in this > error pileup fails. If we can make both fail, we have a crash bug. > Else, we have a harmless API violation. > > Any ideas on how to make the qdev_realize() fail? qemu CLI case QEMU -cpu qemu64,enforce,topoext legacy hotplug case: QEMU -smp 1,maxcpus=2 (monitor) cpu-add 1 (monitor) cpu-add 1 <= fail