commit 2770c90d432b571cab718e28f838097f0b2201ec
author Paolo Bonzini <pbonzini@redhat.com> Fri Dec 22 16:30:34 2017 +0100
committer Paolo Bonzini <pbonzini@redhat.com> Fri Jan 12 09:54:13 2018 +0100
tree ebf68e86e1b04e5ab79d4e0dfa0b2b5f40933d21
parent d9bcd6f7f23a13ea627d8edb85c0706525da0b75

scsi: fix scsi_convert_sense crash when in_buf == NULL && in_len == 0

scsi_disk_emulate_command passes in_buf == NULL when sent a REQUEST
SENSE command.  Check for in_len == 0 before dereferencing in_buf.

Fixes: f68d98b21fa74155dc7c1fd212474379ac3c7531
Reported-by: Roman Kagan <rkagan@virtuozzo.com>
Tested-by: Roman Kagan <rkagan@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

scsi/utils.c

diff --git a/scsi/utils.c b/scsi/utils.c
index ddae650..8738522 100644
--- a/scsi/utils.c
+++ b/scsi/utils.c
@@ -322,18 +322,18 @@
     SCSISense sense;
     bool fixed_in;
 
-    fixed_in = (in_buf[0] & 2) == 0;
-    if (in_len && fixed == fixed_in) {
-        memcpy(buf, in_buf, MIN(len, in_len));
-        return MIN(len, in_len);
+    if (in_len == 0) {
+        return scsi_build_sense_buf(buf, len, SENSE_CODE(NO_SENSE), fixed);
     }
 
-    if (in_len == 0) {
-        sense = SENSE_CODE(NO_SENSE);
+    fixed_in = (in_buf[0] & 2) == 0;
+    if (fixed == fixed_in) {
+        memcpy(buf, in_buf, MIN(len, in_len));
+        return MIN(len, in_len);
     } else {
         sense = scsi_parse_sense_buf(in_buf, in_len);
+        return scsi_build_sense_buf(buf, len, sense, fixed);
     }
-    return scsi_build_sense_buf(buf, len, sense, fixed);
 }
 
 int scsi_sense_to_errno(int key, int asc, int ascq)