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Mon, 11 Jan 2021 13:17:24 +0000 (UTC) Date: Mon, 11 Jan 2021 08:17:24 -0500 (EST) From: Miroslav Rezanina To: Christian Borntraeger Message-ID: <187831554.32408075.1610371044488.JavaMail.zimbra@redhat.com> In-Reply-To: <7631e12a-5422-3167-51fd-1e853a119f8f@de.ibm.com> References: <5acb5521-fdd2-e511-9cc3-176086183dd5@redhat.com> <88c2eb01-f8f5-18d5-6513-57322930cc77@redhat.com> <115622555.32388560.1610368920610.JavaMail.zimbra@redhat.com> <7631e12a-5422-3167-51fd-1e853a119f8f@de.ibm.com> Subject: Re: [RHEL7 qemu-kvm PATCH 2/3] s390x: Fix vm name copy length MIME-Version: 1.0 X-Originating-IP: [10.40.192.93, 10.4.195.18] Thread-Topic: s390x: Fix vm name copy length Thread-Index: k9W4vezOLAHOwZj0sNeDip8SXzp80Q== X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mrezanin@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=216.205.24.124; envelope-from=mrezanin@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.251, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable 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: Thomas Huth , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , qemu-s390x , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" ----- Original Message ----- > From: "Christian Borntraeger" > To: "Thomas Huth" , "Miroslav Rezanina" > Cc: "qemu-s390x" , "Philippe Mathieu-Daud=C3=A9" <= philmd@redhat.com>, qemu-devel@nongnu.org > Sent: Monday, January 11, 2021 2:02:32 PM > Subject: Re: [RHEL7 qemu-kvm PATCH 2/3] s390x: Fix vm name copy length >=20 >=20 >=20 > On 11.01.21 13:54, Thomas Huth wrote: > > On 11/01/2021 13.42, Miroslav Rezanina wrote: > >> > >> > >> ----- Original Message ----- > >>> From: "Thomas Huth" > >>> To: "Philippe Mathieu-Daud=C3=A9" , mrezanin@redha= t.com, > >>> qemu-devel@nongnu.org, "qemu-s390x" > >>> > >>> Sent: Monday, January 11, 2021 1:24:57 PM > >>> Subject: Re: [RHEL7 qemu-kvm PATCH 2/3] s390x: Fix vm name copy lengt= h > >>> > >>> On 11/01/2021 13.10, Philippe Mathieu-Daud=C3=A9 wrote: > >>>> Hi Miroslav, > >>>> > >>>> On 1/11/21 12:30 PM, mrezanin@redhat.com wrote: > >>>>> From: Miroslav Rezanina > >>>>> > >>>>> There are two cases when vm name is copied but closing \0 can be lo= st > >>>>> in case name is too long (>=3D256 characters). > >>>>> > >>>>> Updating length to copy so there is space for closing \0. > >>>>> > >>>>> Signed-off-by: Miroslav Rezanina > >>>>> --- > >>>>> =C2=A0=C2=A0 target/s390x/kvm.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0 | 2 +- > >>>>> =C2=A0=C2=A0 target/s390x/misc_helper.c | 4 +++- > >>>>> =C2=A0=C2=A0 2 files changed, 4 insertions(+), 2 deletions(-) > >>>>> > >>>>> diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c > >>>>> index b8385e6b95..2313b5727e 100644 > >>>>> --- a/target/s390x/kvm.c > >>>>> +++ b/target/s390x/kvm.c > >>>>> @@ -1918,7 +1918,7 @@ static void insert_stsi_3_2_2(S390CPU *cpu, _= _u64 > >>>>> addr, uint8_t ar) > >>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 */ > >>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (qemu_name) { > >>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 strncp= y((char *)sysib.ext_names[0], qemu_name, > >>>>> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0 sizeof(sysib.ext_names[0])); > >>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0 sizeof(sysib.ext_names[0]) - 1); > >>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 } else { > >>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 strcpy= ((char *)sysib.ext_names[0], "KVMguest"); > >>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 } > >>>> > >>>> What about using strpadcpy() instead? > >>> > >>> Yes, strpadcpy is the better way here - this field has to be padded w= ith > >>> zeroes, so doing "- 1" is wrong here. > >> > >> Hi Thomas, > >> > >> as I wrote in reply to Phillipe - the array is memset to zeroes before= the > >> if so we > >> are sure it's padded with zeroes (in this occurrence, not true for sec= ond > >> one). > >=20 > > Ok, but dropping the last character is still wrong here. The ext_names = do > > not need to be terminated with a \0 if they have the full length. > The current code is actually correct. We are perfectly fine without the f= inal > \n if the string is really 256 bytes. >=20 > Replacing memset + strncpy with strpadcpy is certainly a good cleanup. Is= it > necessary? No. Yes, it is necessary because otherwise compiler (GCC 11) produce warning an= d so build fail when --enable-werror is used. Mirek >=20 >=20 --=20 Miroslav Rezanina Software Engineer - Virtualization Team Maintainer