[PATCH-for-6.2 v2 2/2] tests/qtest/fdc-test: Add a regression test for CVE-2021-20196

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

From: Alexander Bulekov <alxndr@bu.edu>

When running 'make check-qtest-i386' with QEMU configured
with '--enable-sanitizers' we get:

  AddressSanitizer:DEADLYSIGNAL
  =================================================================
  ==287878==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000344
  ==287878==The signal is caused by a WRITE memory access.
  ==287878==Hint: address points to the zero page.
      #0 0x564b2e5bac27 in blk_inc_in_flight block/block-backend.c:1346:5
      #1 0x564b2e5bb228 in blk_pwritev_part block/block-backend.c:1317:5
      #2 0x564b2e5bcd57 in blk_pwrite block/block-backend.c:1498:11
      #3 0x564b2ca1cdd3 in fdctrl_write_data hw/block/fdc.c:2221:17
      #4 0x564b2ca1b2f7 in fdctrl_write hw/block/fdc.c:829:9
      #5 0x564b2dc49503 in portio_write softmmu/ioport.c:201:9

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Message-Id: <20210319050906.14875-2-alxndr@bu.edu>
[PMD: Rebased, use global test_image]
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 tests/qtest/fdc-test.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/tests/qtest/fdc-test.c b/tests/qtest/fdc-test.c
index 26b69f7c5cd..dfca84c7b96 100644
--- a/tests/qtest/fdc-test.c
+++ b/tests/qtest/fdc-test.c
@@ -546,6 +546,26 @@ static void fuzz_registers(void)
     }
 }
 
+static void test_cve_2021_20196(void)
+{
+    QTestState *s;
+
+    s = qtest_initf("-nographic -m 32M -nodefaults "
+                    "-drive file=%s,format=raw,if=floppy", test_image);
+    qtest_outw(s, 0x3f2, 0x0004);
+    qtest_outw(s, 0x3f4, 0x0200);
+    qtest_outw(s, 0x3f4, 0x0000);
+    qtest_outw(s, 0x3f4, 0x0000);
+    qtest_outw(s, 0x3f4, 0x0000);
+    qtest_outw(s, 0x3f4, 0x0000);
+    qtest_outw(s, 0x3f4, 0x0000);
+    qtest_outw(s, 0x3f4, 0x0000);
+    qtest_outw(s, 0x3f4, 0x0000);
+    qtest_outw(s, 0x3f4, 0x0000);
+    qtest_outw(s, 0x3f2, 0x0001);
+    qtest_quit(s);
+}
+
 int main(int argc, char **argv)
 {
     int fd;
@@ -576,6 +596,7 @@ int main(int argc, char **argv)
     qtest_add_func("/fdc/read_no_dma_18", test_read_no_dma_18);
     qtest_add_func("/fdc/read_no_dma_19", test_read_no_dma_19);
     qtest_add_func("/fdc/fuzz-registers", fuzz_registers);
+    qtest_add_func("/fdc/fuzz/cve_2021_20196", test_cve_2021_20196);
 
     ret = g_test_run();
 
-- 
2.31.1