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a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1784021702; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=RpqPu6Ft673rxadU8U4q5p7PwhY65vWe7XWmoTLN7tM=; b=U+S43YdK1ZvyJjRNRpAHJPUisgG4eVvp4v3euE0rbJYCfeyjVuk1WXFhhzaUOHXCf6CXUM INM0EALuHuKXPohMqkvHOlK1hzcsmBbIuLT3r2ES8MkF0/R8AkmbFM/CHfGfCAwbFErUxS 0EL1BL+jE1mgChC4S5CusYUFvoljsUk= X-MC-Unique: qtVcUgfdPK29frIrDXJNzQ-1 X-Mimecast-MFC-AGG-ID: qtVcUgfdPK29frIrDXJNzQ_1784021588 From: Cornelia Huck To: qemu-devel@nongnu.org Cc: qemu-s390x@nongnu.org, Christian Borntraeger , qemu-stable@nongnu.org, Matthew Rosato , Eric Farman , Collin Walling , Cornelia Huck Subject: [PULL for-11.1 1/3] s390x/sclp: prevent re-reading the sclp header Date: Tue, 14 Jul 2026 11:32:58 +0200 Message-ID: <20260714093300.2193848-2-cohuck@redhat.com> In-Reply-To: <20260714093300.2193848-1-cohuck@redhat.com> References: <20260714093300.2193848-1-cohuck@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.6 on 10.30.177.95 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists1p.gnu.org; Received-SPF: permerror client-ip=170.10.129.124; envelope-from=cohuck@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 12 X-Spam_score: 1.2 X-Spam_bar: + X-Spam_report: (1.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H2=-0.01, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, T_SPF_PERMERROR=0.01 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1784021713255158500 Content-Type: text/plain; charset="utf-8" From: Christian Borntraeger We verify the sccb length and then allocate based on that length. The following access re-reads the sccb again. This can race against other vCPUs overwriting the length field. sclp_service_call_protected does not need a change as the ultravisor provides a consistent snapshot. Fixes: c1db53a5910f ("s390/sclp: read sccb from mem based on provided lengt= h") Cc: qemu-stable@nongnu.org Signed-off-by: Christian Borntraeger Reviewed-by: Matthew Rosato Reviewed-by: Eric Farman Reviewed-by: Collin Walling Message-ID: <20260709142906.197474-2-borntraeger@linux.ibm.com> Signed-off-by: Cornelia Huck --- hw/s390x/sclp.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/hw/s390x/sclp.c b/hw/s390x/sclp.c index 2d2cde7803ff..3c8cb164888f 100644 --- a/hw/s390x/sclp.c +++ b/hw/s390x/sclp.c @@ -329,7 +329,8 @@ int sclp_service_call(S390CPU *cpu, uint64_t sccb, uint= 32_t code) /* * we want to work on a private copy of the sccb, to prevent guests * from playing dirty tricks by modifying the memory content after - * the host has checked the values + * the host has checked the values. + * Reuse the previously fetched header */ work_sccb =3D g_malloc0(be16_to_cpu(header.length)); ret =3D address_space_read(as, sccb, attrs, @@ -337,6 +338,7 @@ int sclp_service_call(S390CPU *cpu, uint64_t sccb, uint= 32_t code) if (ret !=3D MEMTX_OK) { return -PGM_ADDRESSING; } + work_sccb->h =3D header; =20 if (!sclp_command_code_valid(code)) { work_sccb->h.response_code =3D cpu_to_be16(SCLP_RC_INVALID_SCLP_CO= MMAND); --=20 2.55.0