File 0062-scsi-lsi-exit-infinite-loop-while-e.patch of Package qemu-linux-user

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File 0062-scsi-lsi-exit-infinite-loop-while-e.patch of Package qemu-linux-user

From: Paolo Bonzini <pbonzini@redhat.com>
Date: Wed, 14 Aug 2019 17:35:21 +0530
Subject: 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>
(cherry picked from commit de594e47659029316bbf9391efb79da0a1a08e08)
[BR: BSC#1146873 CVE-2019-12068]
Signed-off-by: Bruce Rogers <brogers@suse.com>
---
 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 e0fea097b9d4a4cb29f8fabc4375..76f76916bb3568af98fea45851e7 100644
--- a/hw/scsi/lsi53c895a.c
+++ b/hw/scsi/lsi53c895a.c
@@ -179,6 +179,9 @@ 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;
@@ -1101,7 +1104,21 @@ 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
@@ -1523,19 +1540,7 @@ 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 {
@@ -1925,6 +1930,10 @@ 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);
@@ -1943,6 +1952,10 @@ 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;

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File 0062-scsi-lsi-exit-infinite-loop-while-e.patch of Package qemu-linux-user

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