From: Mauro Matteo Cascella <mcascell@redhat.com>

Set current_req to NULL, not current_req->req, to prevent reusing a free'd
buffer in case of repeated SCSI cancel requests.  Also apply the fix to
CLEAR QUEUE and BUS DEVICE RESET messages as well, since they also cancel
the request.

Thanks to Alexander Bulekov for providing a reproducer.

Fixes: CVE-2022-0216
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/972
Signed-off-by: Mauro Matteo Cascella <mcascell@redhat.com>
Tested-by: Alexander Bulekov <alxndr@bu.edu>
Message-Id: <20220711123316.421279-1-mcascell@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/scsi/lsi53c895a.c               |  3 +-
 tests/qtest/fuzz-lsi53c895a-test.c | 76 ++++++++++++++++++++++++++++++
 2 files changed, 78 insertions(+), 1 deletion(-)

diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c
index 99ea42d49b..ad5f5e5f39 100644
--- a/hw/scsi/lsi53c895a.c
+++ b/hw/scsi/lsi53c895a.c
@@ -1030,7 +1030,7 @@ static void lsi_do_msgout(LSIState *s)
             trace_lsi_do_msgout_abort(current_tag);
             if (current_req && current_req->req) {
                 scsi_req_cancel(current_req->req);
-                current_req->req = NULL;
+                current_req = NULL;
             }
             lsi_disconnect(s);
             break;
@@ -1056,6 +1056,7 @@ static void lsi_do_msgout(LSIState *s)
             /* clear the current I/O process */
             if (s->current) {
                 scsi_req_cancel(s->current->req);
+                current_req = NULL;
             }
 
             /* As the current implemented devices scsi_disk and scsi_generic
diff --git a/tests/qtest/fuzz-lsi53c895a-test.c b/tests/qtest/fuzz-lsi53c895a-test.c
index 2e8e67859e..b23d3ecf45 100644
--- a/tests/qtest/fuzz-lsi53c895a-test.c
+++ b/tests/qtest/fuzz-lsi53c895a-test.c
@@ -8,6 +8,79 @@
 #include "qemu/osdep.h"
 #include "libqtest.h"
 
+/*
+ * This used to trigger a UAF in lsi_do_msgout()
+ * https://gitlab.com/qemu-project/qemu/-/issues/972
+ */
+static void test_lsi_do_msgout_cancel_req(void)
+{
+    QTestState *s;
+
+    if (sizeof(void *) == 4) {
+        g_test_skip("memory size too big for 32-bit build");
+        return;
+    }
+
+    s = qtest_init("-M q35 -m 4G -display none -nodefaults "
+                   "-device lsi53c895a,id=scsi "
+                   "-device scsi-hd,drive=disk0 "
+                   "-drive file=null-co://,id=disk0,if=none,format=raw");
+
+    qtest_outl(s, 0xcf8, 0x80000810);
+    qtest_outl(s, 0xcf8, 0xc000);
+    qtest_outl(s, 0xcf8, 0x80000810);
+    qtest_outw(s, 0xcfc, 0x7);
+    qtest_outl(s, 0xcf8, 0x80000810);
+    qtest_outl(s, 0xcfc, 0xc000);
+    qtest_outl(s, 0xcf8, 0x80000804);
+    qtest_outw(s, 0xcfc, 0x05);
+    qtest_writeb(s, 0x69736c10, 0x08);
+    qtest_writeb(s, 0x69736c13, 0x58);
+    qtest_writeb(s, 0x69736c1a, 0x01);
+    qtest_writeb(s, 0x69736c1b, 0x06);
+    qtest_writeb(s, 0x69736c22, 0x01);
+    qtest_writeb(s, 0x69736c23, 0x07);
+    qtest_writeb(s, 0x69736c2b, 0x02);
+    qtest_writeb(s, 0x69736c48, 0x08);
+    qtest_writeb(s, 0x69736c4b, 0x58);
+    qtest_writeb(s, 0x69736c52, 0x04);
+    qtest_writeb(s, 0x69736c53, 0x06);
+    qtest_writeb(s, 0x69736c5b, 0x02);
+    qtest_outl(s, 0xc02d, 0x697300);
+    qtest_writeb(s, 0x5a554662, 0x01);
+    qtest_writeb(s, 0x5a554663, 0x07);
+    qtest_writeb(s, 0x5a55466a, 0x10);
+    qtest_writeb(s, 0x5a55466b, 0x22);
+    qtest_writeb(s, 0x5a55466c, 0x5a);
+    qtest_writeb(s, 0x5a55466d, 0x5a);
+    qtest_writeb(s, 0x5a55466e, 0x34);
+    qtest_writeb(s, 0x5a55466f, 0x5a);
+    qtest_writeb(s, 0x5a345a5a, 0x77);
+    qtest_writeb(s, 0x5a345a5b, 0x55);
+    qtest_writeb(s, 0x5a345a5c, 0x51);
+    qtest_writeb(s, 0x5a345a5d, 0x27);
+    qtest_writeb(s, 0x27515577, 0x41);
+    qtest_outl(s, 0xc02d, 0x5a5500);
+    qtest_writeb(s, 0x364001d0, 0x08);
+    qtest_writeb(s, 0x364001d3, 0x58);
+    qtest_writeb(s, 0x364001da, 0x01);
+    qtest_writeb(s, 0x364001db, 0x26);
+    qtest_writeb(s, 0x364001dc, 0x0d);
+    qtest_writeb(s, 0x364001dd, 0xae);
+    qtest_writeb(s, 0x364001de, 0x41);
+    qtest_writeb(s, 0x364001df, 0x5a);
+    qtest_writeb(s, 0x5a41ae0d, 0xf8);
+    qtest_writeb(s, 0x5a41ae0e, 0x36);
+    qtest_writeb(s, 0x5a41ae0f, 0xd7);
+    qtest_writeb(s, 0x5a41ae10, 0x36);
+    qtest_writeb(s, 0x36d736f8, 0x0c);
+    qtest_writeb(s, 0x36d736f9, 0x80);
+    qtest_writeb(s, 0x36d736fa, 0x0d);
+    qtest_outl(s, 0xc02d, 0x364000);
+
+    qtest_quit(s);
+}
+
 /*
  * This used to trigger the assert in lsi_do_dma()
  * https://bugs.launchpad.net/qemu/+bug/697510
@@ -44,5 +117,8 @@ int main(int argc, char **argv)
     qtest_add_func("fuzz/lsi53c895a/lsi_do_dma_empty_queue",
                    test_lsi_do_dma_empty_queue);
 
+    qtest_add_func("fuzz/lsi53c895a/lsi_do_msgout_cancel_req",
+                   test_lsi_do_msgout_cancel_req);
+
     return g_test_run();
 }
-- 
2.36.1