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[88.21.205.47]) by smtp.gmail.com with ESMTPSA id h21sm1070908ejq.83.2020.03.04.06.12.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Mar 2020 06:12:39 -0800 (PST) Subject: Re: [PATCH 1/2] misc: Replace zero-length arrays with flexible array member (automatic) To: Paolo Bonzini , qemu-devel@nongnu.org References: <20200304005105.27454-1-philmd@redhat.com> <20200304005105.27454-2-philmd@redhat.com> <1e1a1491-15ca-29d4-8bd6-1bf14edb4ad5@redhat.com> <38b55649-b1cd-8891-5c13-ec4c6ef3ae5e@redhat.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: Date: Wed, 4 Mar 2020 15:12:36 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <38b55649-b1cd-8891-5c13-ec4c6ef3ae5e@redhat.com> Content-Language: en-US X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 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 , Peter Maydell , "Michael S. Tsirkin" , Jason Wang , Yuval Shaia , Gerd Hoffmann , Stefano Stabellini , qemu-block@nongnu.org, David Hildenbrand , "Gustavo A . R . Silva" , Halil Pasic , Christian Borntraeger , "Gonglei \(Arei\)" , Anthony Perard , =?UTF-8?Q?Marc-Andr=c3=a9_Lureau?= , David Gibson , Thomas Huth , Eduardo Habkost , Paul Durrant , Eric Auger , qemu-s390x@nongnu.org, qemu-arm@nongnu.org, xen-devel@lists.xenproject.org, John Snow , Richard Henderson , Kevin Wolf , Xiao Guangrong , Cornelia Huck , Laurent Vivier , Max Reitz , Igor Mammedov Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 3/4/20 2:44 PM, Paolo Bonzini wrote: > On 04/03/20 14:12, Philippe Mathieu-Daud=C3=A9 wrote: >> >> hw/scsi/spapr_vscsi.c:69:29: error: field 'iu' with variable sized type >> 'union viosrp_iu' not at the end of a struct or class is a GNU extension >> [-Werror,-Wgnu-variable-sized-type-not-at-end] >> =C2=A0=C2=A0=C2=A0 union viosrp_iu=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0 iu; >> =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=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0 ^ >> >> Yay we found a bug! Thanks Gustavo :) >> >> union srp_iu { >> =C2=A0=C2=A0=C2=A0 struct srp_login_req login_req; >> =C2=A0=C2=A0=C2=A0 struct srp_login_rsp login_rsp; >> =C2=A0=C2=A0=C2=A0 struct srp_login_rej login_rej; >> =C2=A0=C2=A0=C2=A0 struct srp_i_logout i_logout; >> =C2=A0=C2=A0=C2=A0 struct srp_t_logout t_logout; >> =C2=A0=C2=A0=C2=A0 struct srp_tsk_mgmt tsk_mgmt; >> =C2=A0=C2=A0=C2=A0 struct srp_cmd cmd; >> =C2=A0=C2=A0=C2=A0 struct srp_rsp rsp; >> =C2=A0=C2=A0=C2=A0 uint8_t reserved[SRP_MAX_IU_LEN]; >> }; >=20 > It's variable-sized but it's okay as long as the total size doesn't > exceed SRP_MAX_IU_LEN. So it's not a bug, but I agree it's a time bomb. > Moving the field last should work, but it would still be quite > dangerous code. Yeah I reached the same conclusion. I'll send a fix for the dangerous code. Do you want to drop this series, or only the change in 'struct srp_rsp'=20 (or in all hw/scsi/srp.h). Actually I guess it makes sense I move the=20 'hw/scsi/srp.h' changes with the series cleaning dangerous code.