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From 212c129b82f0a53725a4167303de2ee0a865f82d Mon Sep 17 00:00:00 2001
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From: Thomas Huth <thuth@redhat.com>
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Date: Wed, 11 Nov 2020 12:03:08 -0500
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Subject: [PATCH 08/18] s390/sclp: read sccb from mem based on provided length
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RH-Author: Thomas Huth <thuth@redhat.com>
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Message-id: <20201111120316.707489-5-thuth@redhat.com>
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Patchwork-id: 99501
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O-Subject: [RHEL-8.4.0 qemu-kvm PATCH v2 04/12] s390/sclp: read sccb from mem based on provided length
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Bugzilla: 1798506
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RH-Acked-by: Jens Freimann <jfreimann@redhat.com>
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RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
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RH-Acked-by: David Hildenbrand <david@redhat.com>
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From: Collin Walling <walling@linux.ibm.com>
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The header contained within the SCCB passed to the SCLP service call
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contains the actual length of the SCCB. Instead of allocating a static
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4K size for the work sccb, let's allow for a variable size determined
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by the value in the header. The proper checks are already in place to
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ensure the SCCB length is sufficent to store a full response and that
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the length does not cross any explicitly-set boundaries.
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Signed-off-by: Collin Walling <walling@linux.ibm.com>
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Reviewed-by: Thomas Huth <thuth@redhat.com>
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Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
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Message-Id: <20200915194416.107460-4-walling@linux.ibm.com>
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Signed-off-by: Cornelia Huck <cohuck@redhat.com>
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(cherry picked from commit c1db53a5910f988eeb32f031c53a50f3373fd824)
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Signed-off-by: Thomas Huth <thuth@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 hw/s390x/event-facility.c |  2 +-
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 hw/s390x/sclp.c           | 55 ++++++++++++++++++++++-----------------
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 include/hw/s390x/sclp.h   |  2 +-
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 3 files changed, 33 insertions(+), 26 deletions(-)
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diff --git a/hw/s390x/event-facility.c b/hw/s390x/event-facility.c
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index 66205697ae7..8aa7017f06b 100644
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--- a/hw/s390x/event-facility.c
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+++ b/hw/s390x/event-facility.c
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@@ -215,7 +215,7 @@ static uint16_t handle_sccb_read_events(SCLPEventFacility *ef, SCCB *sccb,
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     event_buf = &red->ebh;
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     event_buf->length = 0;
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-    slen = sizeof(sccb->data);
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+    slen = sccb_data_len(sccb);
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     rc = SCLP_RC_NO_EVENT_BUFFERS_STORED;
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diff --git a/hw/s390x/sclp.c b/hw/s390x/sclp.c
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index 38278497319..cf1292beb22 100644
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--- a/hw/s390x/sclp.c
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+++ b/hw/s390x/sclp.c
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@@ -231,25 +231,29 @@ int sclp_service_call_protected(CPUS390XState *env, uint64_t sccb,
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 {
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     SCLPDevice *sclp = get_sclp_device();
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     SCLPDeviceClass *sclp_c = SCLP_GET_CLASS(sclp);
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-    SCCB work_sccb;
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-    hwaddr sccb_len = sizeof(SCCB);
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+    SCCBHeader header;
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+    g_autofree SCCB *work_sccb = NULL;
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-    s390_cpu_pv_mem_read(env_archcpu(env), 0, &work_sccb, sccb_len);
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+    s390_cpu_pv_mem_read(env_archcpu(env), 0, &header, sizeof(SCCBHeader));
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+
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+    work_sccb = g_malloc0(be16_to_cpu(header.length));
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+    s390_cpu_pv_mem_read(env_archcpu(env), 0, work_sccb,
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+                         be16_to_cpu(header.length));
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     if (!sclp_command_code_valid(code)) {
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-        work_sccb.h.response_code = cpu_to_be16(SCLP_RC_INVALID_SCLP_COMMAND);
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+        work_sccb->h.response_code = cpu_to_be16(SCLP_RC_INVALID_SCLP_COMMAND);
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         goto out_write;
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     }
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-    if (!sccb_verify_boundary(sccb, be16_to_cpu(work_sccb.h.length))) {
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-        work_sccb.h.response_code = cpu_to_be16(SCLP_RC_SCCB_BOUNDARY_VIOLATION);
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+    if (!sccb_verify_boundary(sccb, be16_to_cpu(work_sccb->h.length))) {
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+        work_sccb->h.response_code = cpu_to_be16(SCLP_RC_SCCB_BOUNDARY_VIOLATION);
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         goto out_write;
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     }
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-    sclp_c->execute(sclp, &work_sccb, code);
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+    sclp_c->execute(sclp, work_sccb, code);
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 out_write:
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-    s390_cpu_pv_mem_write(env_archcpu(env), 0, &work_sccb,
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-                          be16_to_cpu(work_sccb.h.length));
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+    s390_cpu_pv_mem_write(env_archcpu(env), 0, work_sccb,
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+                          be16_to_cpu(work_sccb->h.length));
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     sclp_c->service_interrupt(sclp, SCLP_PV_DUMMY_ADDR);
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     return 0;
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 }
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@@ -258,9 +262,8 @@ int sclp_service_call(CPUS390XState *env, uint64_t sccb, uint32_t code)
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 {
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     SCLPDevice *sclp = get_sclp_device();
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     SCLPDeviceClass *sclp_c = SCLP_GET_CLASS(sclp);
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-    SCCB work_sccb;
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-
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-    hwaddr sccb_len = sizeof(SCCB);
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+    SCCBHeader header;
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+    g_autofree SCCB *work_sccb = NULL;
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     /* first some basic checks on program checks */
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     if (env->psw.mask & PSW_MASK_PSTATE) {
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@@ -274,32 +277,36 @@ int sclp_service_call(CPUS390XState *env, uint64_t sccb, uint32_t code)
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         return -PGM_SPECIFICATION;
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     }
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+    /* the header contains the actual length of the sccb */
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+    cpu_physical_memory_read(sccb, &header, sizeof(SCCBHeader));
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+
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+    /* Valid sccb sizes */
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+    if (be16_to_cpu(header.length) < sizeof(SCCBHeader)) {
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+        return -PGM_SPECIFICATION;
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+    }
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+
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     /*
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      * we want to work on a private copy of the sccb, to prevent guests
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      * from playing dirty tricks by modifying the memory content after
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      * the host has checked the values
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      */
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-    cpu_physical_memory_read(sccb, &work_sccb, sccb_len);
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-
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-    /* Valid sccb sizes */
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-    if (be16_to_cpu(work_sccb.h.length) < sizeof(SCCBHeader)) {
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-        return -PGM_SPECIFICATION;
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-    }
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+    work_sccb = g_malloc0(be16_to_cpu(header.length));
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+    cpu_physical_memory_read(sccb, work_sccb, be16_to_cpu(header.length));
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     if (!sclp_command_code_valid(code)) {
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-        work_sccb.h.response_code = cpu_to_be16(SCLP_RC_INVALID_SCLP_COMMAND);
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+        work_sccb->h.response_code = cpu_to_be16(SCLP_RC_INVALID_SCLP_COMMAND);
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         goto out_write;
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     }
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-    if (!sccb_verify_boundary(sccb, be16_to_cpu(work_sccb.h.length))) {
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-        work_sccb.h.response_code = cpu_to_be16(SCLP_RC_SCCB_BOUNDARY_VIOLATION);
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+    if (!sccb_verify_boundary(sccb, be16_to_cpu(work_sccb->h.length))) {
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+        work_sccb->h.response_code = cpu_to_be16(SCLP_RC_SCCB_BOUNDARY_VIOLATION);
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         goto out_write;
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     }
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-    sclp_c->execute(sclp, &work_sccb, code);
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+    sclp_c->execute(sclp, work_sccb, code);
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 out_write:
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-    cpu_physical_memory_write(sccb, &work_sccb,
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-                              be16_to_cpu(work_sccb.h.length));
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+    cpu_physical_memory_write(sccb, work_sccb,
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+                              be16_to_cpu(work_sccb->h.length));
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     sclp_c->service_interrupt(sclp, sccb);
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diff --git a/include/hw/s390x/sclp.h b/include/hw/s390x/sclp.h
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index c0a3faa37d7..55f53a46540 100644
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--- a/include/hw/s390x/sclp.h
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+++ b/include/hw/s390x/sclp.h
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@@ -177,7 +177,7 @@ typedef struct IoaCfgSccb {
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 typedef struct SCCB {
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     SCCBHeader h;
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-    char data[SCCB_DATA_LEN];
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+    char data[];
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  } QEMU_PACKED SCCB;
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 #define TYPE_SCLP "sclp"
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-- 
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2.27.0
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