From: P J P <ppandit@redhat.com>
Date: Thu,  6 Dec 2018 14:18:16 +0530
Message-Id: <20181206084816.30485-1-ppandit@redhat.com>
MIME-Version: 1.0
Content-Transfer-Encoding: quoted-printable
Subject: [Qemu-devel] [PATCH] i2c: pm_smbus: check smb_index before block
 transfer write
To: Qemu Developers <qemu-devel@nongnu.org>
Cc: "Michael S . Tsirkin" <mst@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Michael Hanselmann <public@hansmi.ch>, Prasad J Pandit <pjp@fedoraproject.org>

From: Prasad J Pandit <pjp@fedoraproject.org>

While performing block transfer write in smb_ioport_writeb(),
'smb_index' is incremented and used to index smb_data[] array.
Check 'smb_index' value to avoid OOB access.

Reported-by: Michael Hanselmann <public@hansmi.ch>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 hw/i2c/pm_smbus.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/hw/i2c/pm_smbus.c b/hw/i2c/pm_smbus.c
index 685a2378ed..03062740cc 100644
--- a/hw/i2c/pm_smbus.c
+++ b/hw/i2c/pm_smbus.c
@@ -240,6 +240,9 @@ static void smb_ioport_writeb(void *opaque, hwaddr ad=
dr, uint64_t val,
             uint8_t read =3D s->smb_addr & 0x01;
=20
             s->smb_index++;
+            if (s->smb_index >=3D PM_SMBUS_MAX_MSG_SIZE) {
+                s->smb_index =3D 0;
+            }
             if (!read && s->smb_index =3D=3D s->smb_data0) {
                 uint8_t prot =3D (s->smb_ctl >> 2) & 0x07;
                 uint8_t cmd =3D s->smb_cmd;
--=20
2.19.2