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Sat, 27 Jun 2020 11:57:08 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 2269211384A6; Sat, 27 Jun 2020 13:57:07 +0200 (CEST) From: Markus Armbruster To: Vladimir Sementsov-Ogievskiy Subject: Re: [PATCH 06/46] error: Avoid error_propagate() when error is not used here References: <20200624164344.3778251-1-armbru@redhat.com> <20200624164344.3778251-7-armbru@redhat.com> <45536875-9cf2-72d5-b555-8b8b1992085b@virtuozzo.com> Date: Sat, 27 Jun 2020 13:57:07 +0200 In-Reply-To: <45536875-9cf2-72d5-b555-8b8b1992085b@virtuozzo.com> (Vladimir Sementsov-Ogievskiy's message of "Fri, 26 Jun 2020 17:36:27 +0300") Message-ID: <87eeq0rab0.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=205.139.110.120; envelope-from=armbru@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/27 07:57:11 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: peter.maydell@linaro.org, berrange@redhat.com, ehabkost@redhat.com, qemu-block@nongnu.org, qemu-devel@nongnu.org, pbonzini@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Vladimir Sementsov-Ogievskiy writes: > 24.06.2020 19:43, Markus Armbruster wrote: >> When all we do with an Error we receive into a local variable is >> propagating to somewhere else, we can just as well receive it there >> right away. Coccinelle script: >> >> @@ >> identifier fun, err, errp; >> expression list args; >> @@ >> - fun(args, &err); >> + fun(args, errp); >> ... when != err >> when strict >> - error_propagate(errp, err); >> >> @@ >> identifier fun, err, errp; >> expression list args; >> expression ret; >> @@ >> - ret = fun(args, &err); >> + ret = fun(args, errp); >> ... when != err >> when strict >> - error_propagate(errp, err); >> >> @@ >> identifier fun, err, errp; >> expression list args; >> expression ret; >> @@ >> - ret = fun(args, &err); >> + ret = fun(args, errp); >> ... when != err >> when strict >> if ( >> ( >> ret >> | >> !ret >> | >> ret == 0 >> | >> ret != 0 >> | >> ret < 0 >> | >> ret != NULL >> | >> ret == NULL >> ) >> ) >> { >> ... when != err >> when strict >> - error_propagate(errp, err); >> ... >> } >> >> @@ >> identifier fun, err, errp; >> expression list args; >> @@ >> if ( >> ( >> - fun(args, &err) >> + fun(args, errp) >> | >> - !fun(args, &err) >> + !fun(args, errp) >> | >> - fun(args, &err) == 0 >> + fun(args, errp) == 0 >> | >> - fun(args, &err) != 0 >> + fun(args, errp) != 0 >> | >> - fun(args, &err) < 0 >> + fun(args, errp) < 0 >> | >> - fun(args, &err) == NULL >> + fun(args, errp) == NULL >> | >> - fun(args, &err) != NULL >> + fun(args, errp) != NULL >> ) >> ) >> { >> ... when != err; >> when strict >> - error_propagate(errp, err); >> ... >> } >> >> The first two rules are prone to fail with "error_propagate(...) >> ... reachable by inconsistent control-flow paths". Script without >> them re-run where that happens. >> >> Manually double-check @err is not used afterwards. Dereferencing it >> would be use after free, but checking whether it's null would be >> legitimate. One such change to qbus_realize() backed out. >> >> Suboptimal line breaks tweaked manually. >> >> Signed-off-by: Markus Armbruster >> --- > > [..] > >> diff --git a/hw/intc/xics_kvm.c b/hw/intc/xics_kvm.c >> index 8d6156578f..6705220380 100644 >> --- a/hw/intc/xics_kvm.c >> +++ b/hw/intc/xics_kvm.c >> @@ -316,9 +316,8 @@ int ics_set_kvm_state(ICSState *ics, Error **errp) >> continue; >> } > > local_err becomes unused in this function, we should drop it Will fix. > with this fixed: > Reviewed-by: Vladimir Sementsov-Ogievskiy Thanks! > >> - ret = ics_set_kvm_state_one(ics, i, &local_err); >> + ret = ics_set_kvm_state_one(ics, i, errp); >> if (ret < 0) { >> - error_propagate(errp, local_err); >> return ret; >> } >> }