From 60b05771b8afc08e0ca9956658d2c55cd1739652 Mon Sep 17 00:00:00 2001
From: Mauro Matteo Cascella <mcascell@redhat.com>
Date: Thu, 4 Nov 2021 17:31:38 +0100
Subject: [PATCH 1/2] hw/scsi/scsi-disk: MODE_PAGE_ALLS not allowed in MODE
 SELECT commands
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RH-Author: Jon Maloy <jmaloy@redhat.com>
RH-MergeRequest: 70: hw/scsi/scsi-disk: MODE_PAGE_ALLS not allowed in MODE SELECT commands
RH-Commit: [1/1] bd3de8bdf48aa6c522612505d08c23dafb122a34 (jmaloy/qemu-kvm)
RH-Bugzilla: 2025605
RH-Acked-by: Paolo Bonzini <None>
RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
RH-Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>

This avoids an off-by-one read of 'mode_sense_valid' buffer in
hw/scsi/scsi-disk.c:mode_sense_page().

Fixes: CVE-2021-3930
Cc: qemu-stable@nongnu.org
Reported-by: Alexander Bulekov <alxndr@bu.edu>
Fixes: a8f4bbe2900 ("scsi-disk: store valid mode pages in a table")
Fixes: #546
Reported-by: Qiuhao Li <Qiuhao.Li@outlook.com>
Signed-off-by: Mauro Matteo Cascella <mcascell@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit b3af7fdf9cc537f8f0dd3e2423d83f5c99a457e8)
Signed-off-by: Jon Maloy <jmaloy@redhat.com>
---
 hw/scsi/scsi-disk.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index 5cb5fd35bd..1d0ea72289 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -1086,6 +1086,7 @@ static int mode_sense_page(SCSIDiskState *s, int page, uint8_t **p_outbuf,
     uint8_t *p = *p_outbuf + 2;
     int length;
 
+    assert(page < ARRAY_SIZE(mode_sense_valid));
     if ((mode_sense_valid[page] & (1 << s->qdev.type)) == 0) {
         return -1;
     }
@@ -1427,6 +1428,11 @@ static int scsi_disk_check_mode_select(SCSIDiskState *s, int page,
         return -1;
     }
 
+    /* MODE_PAGE_ALLS is only valid for MODE SENSE commands */
+    if (page == MODE_PAGE_ALLS) {
+        return -1;
+    }
+
     p = mode_current;
     memset(mode_current, 0, inlen + 2);
     len = mode_sense_page(s, page, &p, 0);
-- 
2.27.0

