[PATCH] hw/scsi/scsi-disk: MODE_PAGE_ALLS not allowed in MODE SELECT commands

From: Mauro Matteo Cascella <mcascell@redhat.com>
To: qemu-devel@nongnu.org
Cc: pbonzini@redhat.com, mcascell@redhat.com, qiuhao.li@outlook.com
Subject: [PATCH] hw/scsi/scsi-disk: MODE_PAGE_ALLS not allowed in MODE SELECT commands
Date: Fri,  5 Nov 2021 12:37:29 +0100	[thread overview]
Message-ID: <20211105113729.530200-1-mcascell@redhat.com> (raw)

MODE_PAGE_ALLS causes an off-by-one error in mode_sense_page() when accessing
the stack-allocated mode_sense_valid buffer. MODE_PAGE_ALLS is only valid for
MODE SENSE commands. Do not process it in MODE SELECT commands.

Fixes: CVE-2021-3930
RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=2020588
Signed-off-by: Mauro Matteo Cascella <mcascell@redhat.com>
Reported-by: Qiuhao Li <qiuhao.li@outlook.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 e8a547dbb7..5852e8dcfd 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -1087,6 +1087,7 @@ static int mode_sense_page(SCSIDiskState *s, int page, uint8_t **p_outbuf,
     uint8_t *p = *p_outbuf + 2;
     int length;
 
+    assert(page != MODE_PAGE_ALLS);
     if ((mode_sense_valid[page] & (1 << s->qdev.type)) == 0) {
         return -1;
     }
@@ -1428,6 +1429,11 @@ 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);
-- 
2.31.1


