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authorPaolo Bonzini <pbonzini@redhat.com>2019-08-14 17:35:21 +0530
committerPaolo Bonzini <pbonzini@redhat.com>2019-08-20 20:00:52 +0200
commitde594e47659029316bbf9391efb79da0a1a08e08 (patch)
tree22f8f2a895bcf13ac6b57d574b48a44344bfa99b /hw/scsi/lsi53c895a.c
parenta060297822ea6b4194bf36654e58c802448a3eea (diff)
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scsi: lsi: exit infinite loop while executing script (CVE-2019-12068)
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 <bugs-syssec@rub.de> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'hw/scsi/lsi53c895a.c')
-rw-r--r--hw/scsi/lsi53c895a.c41
1 files changed, 27 insertions, 14 deletions
diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c
index 222a286..ec53b14 100644
--- a/hw/scsi/lsi53c895a.c
+++ b/hw/scsi/lsi53c895a.c
@@ -186,6 +186,9 @@ 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;
@@ -1133,7 +1136,21 @@ 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
@@ -1570,19 +1587,7 @@ 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 {
@@ -1970,6 +1975,10 @@ 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);
@@ -1988,6 +1997,10 @@ 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;