tests/qtest/fuzz-megasas-test: Add test for GitLab issue #521

Without the previous commit, this test triggers:

  $ make check-qtest-x86_64
  [...]
  Running test qtest-x86_64/fuzz-megasas-test
  qemu-system-x86_64: softmmu/physmem.c:3229: address_space_unmap: Assertion `mr != NULL' failed.
  Broken pipe
  ERROR qtest-x86_64/fuzz-megasas-test - too few tests run (expected 2, got 1)

Suggested-by: Alexander Bulekov <alxndr@bu.edu>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Message-Id: <20211119201141.532377-3-philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tests/qtest/fuzz-megasas-test.c

@@ -34,6 +34,34 @@ static void test_lp1878263_megasas_zero_iov_cnt(void)
     qtest_quit(s);
 }
 
+/*
+ * Overflow SGL buffer.
+ * https://gitlab.com/qemu-project/qemu/-/issues/521
+ */
+static void test_gitlab_issue521_megasas_sgl_ovf(void)
+{
+    QTestState *s = qtest_init("-display none -m 32M -machine q35 "
+                               "-nodefaults -device megasas "
+                               "-device scsi-cd,drive=null0 "
+                               "-blockdev "
+                               "driver=null-co,read-zeroes=on,node-name=null0");
+    qtest_outl(s, 0xcf8, 0x80000818);
+    qtest_outl(s, 0xcfc, 0xc000);
+    qtest_outl(s, 0xcf8, 0x80000804);
+    qtest_outw(s, 0xcfc, 0x05);
+    qtest_bufwrite(s, 0x0, "\x01", 0x1);
+    qtest_bufwrite(s, 0x7, "\x01", 0x1);
+    qtest_bufwrite(s, 0x10, "\x02", 0x1);
+    qtest_bufwrite(s, 0x16, "\x01", 0x1);
+    qtest_bufwrite(s, 0x28, "\x01", 0x1);
+    qtest_bufwrite(s, 0x33, "\x01", 0x1);
+    qtest_outb(s, 0xc040, 0x0);
+    qtest_outb(s, 0xc040, 0x20);
+    qtest_outl(s, 0xc040, 0x20000000);
+    qtest_outb(s, 0xc040, 0x20);
+    qtest_quit(s);
+}
+
 int main(int argc, char **argv)
 {
     const char *arch = qtest_get_arch();
@@ -43,6 +71,8 @@ int main(int argc, char **argv)
     if (strcmp(arch, "i386") == 0 || strcmp(arch, "x86_64") == 0) {
         qtest_add_func("fuzz/test_lp1878263_megasas_zero_iov_cnt",
                        test_lp1878263_megasas_zero_iov_cnt);
+        qtest_add_func("fuzz/gitlab_issue521_megasas_sgl_ovf",
+                       test_gitlab_issue521_megasas_sgl_ovf);
     }
 
     return g_test_run();