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Tue, 05 Nov 2019 20:53:22 +0000 Received: from b01ledav002.gho.pok.ibm.com (b01ledav002.gho.pok.ibm.com [9.57.199.107]) by b01cxnp23034.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id xA5KrIHl53871066 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 5 Nov 2019 20:53:18 GMT Received: from b01ledav002.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 70D46124052; Tue, 5 Nov 2019 20:53:18 +0000 (GMT) Received: from b01ledav002.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5D6AE12405B; Tue, 5 Nov 2019 20:53:18 +0000 (GMT) Received: from localhost (unknown [9.53.179.218]) by b01ledav002.gho.pok.ibm.com (Postfix) with ESMTP; Tue, 5 Nov 2019 20:53:18 +0000 (GMT) From: Michael Roth To: qemu-devel@nongnu.org Subject: [PATCH 54/55] scsi: lsi: exit infinite loop while executing script (CVE-2019-12068) Date: Tue, 5 Nov 2019 14:52:42 -0600 Message-Id: <20191105205243.3766-55-mdroth@linux.vnet.ibm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191105205243.3766-1-mdroth@linux.vnet.ibm.com> References: <20191105205243.3766-1-mdroth@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-11-05_07:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1911050170 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] [fuzzy] X-Received-From: 148.163.156.1 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paolo Bonzini , qemu-stable@nongnu.org, Prasad J Pandit Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Paolo Bonzini When executing script in lsi_execute_script(), the LSI scsi adapter emulator advances 's->dsp' index to read next opcode. This can lead to an infinite loop if the next opcode is empty. Move the existing loop exit after 10k iterations so that it covers no-op opcodes as well. Reported-by: Bugs SysSec Signed-off-by: Paolo Bonzini Signed-off-by: Prasad J Pandit Signed-off-by: Paolo Bonzini (cherry picked from commit de594e47659029316bbf9391efb79da0a1a08e08) Signed-off-by: Michael Roth --- hw/scsi/lsi53c895a.c | 41 +++++++++++++++++++++++++++-------------- 1 file changed, 27 insertions(+), 14 deletions(-) diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c index 10468c1ec1..72f7b59ab5 100644 --- a/hw/scsi/lsi53c895a.c +++ b/hw/scsi/lsi53c895a.c @@ -185,6 +185,9 @@ static const char *names[] = { /* Flag set if this is a tagged command. */ #define LSI_TAG_VALID (1 << 16) +/* Maximum instructions to process. */ +#define LSI_MAX_INSN 10000 + typedef struct lsi_request { SCSIRequest *req; uint32_t tag; @@ -1132,7 +1135,21 @@ static void lsi_execute_script(LSIState *s) s->istat1 |= LSI_ISTAT1_SRUN; again: - insn_processed++; + if (++insn_processed > LSI_MAX_INSN) { + /* Some windows drivers make the device spin waiting for a memory + location to change. If we have been executed a lot of code then + assume this is the case and force an unexpected device disconnect. + This is apparently sufficient to beat the drivers into submission. + */ + if (!(s->sien0 & LSI_SIST0_UDC)) { + qemu_log_mask(LOG_GUEST_ERROR, + "lsi_scsi: inf. loop with UDC masked"); + } + lsi_script_scsi_interrupt(s, LSI_SIST0_UDC, 0); + lsi_disconnect(s); + trace_lsi_execute_script_stop(); + return; + } insn = read_dword(s, s->dsp); if (!insn) { /* If we receive an empty opcode increment the DSP by 4 bytes @@ -1569,19 +1586,7 @@ again: } } } - if (insn_processed > 10000 && s->waiting == LSI_NOWAIT) { - /* Some windows drivers make the device spin waiting for a memory - location to change. If we have been executed a lot of code then - assume this is the case and force an unexpected device disconnect. - This is apparently sufficient to beat the drivers into submission. - */ - if (!(s->sien0 & LSI_SIST0_UDC)) { - qemu_log_mask(LOG_GUEST_ERROR, - "lsi_scsi: inf. loop with UDC masked"); - } - lsi_script_scsi_interrupt(s, LSI_SIST0_UDC, 0); - lsi_disconnect(s); - } else if (s->istat1 & LSI_ISTAT1_SRUN && s->waiting == LSI_NOWAIT) { + if (s->istat1 & LSI_ISTAT1_SRUN && s->waiting == LSI_NOWAIT) { if (s->dcntl & LSI_DCNTL_SSM) { lsi_script_dma_interrupt(s, LSI_DSTAT_SSI); } else { @@ -1969,6 +1974,10 @@ static void lsi_reg_writeb(LSIState *s, int offset, uint8_t val) case 0x2f: /* DSP[24:31] */ s->dsp &= 0x00ffffff; s->dsp |= val << 24; + /* + * FIXME: if s->waiting != LSI_NOWAIT, this will only execute one + * instruction. Is this correct? + */ if ((s->dmode & LSI_DMODE_MAN) == 0 && (s->istat1 & LSI_ISTAT1_SRUN) == 0) lsi_execute_script(s); @@ -1987,6 +1996,10 @@ static void lsi_reg_writeb(LSIState *s, int offset, uint8_t val) break; case 0x3b: /* DCNTL */ s->dcntl = val & ~(LSI_DCNTL_PFF | LSI_DCNTL_STD); + /* + * FIXME: if s->waiting != LSI_NOWAIT, this will only execute one + * instruction. Is this correct? + */ if ((val & LSI_DCNTL_STD) && (s->istat1 & LSI_ISTAT1_SRUN) == 0) lsi_execute_script(s); break; -- 2.17.1