[LTP] [PATCH v2 3/4] ioctl_sg01: Pollute free memory in setup

[Martin Doucha]

The test wasn't reliable if most of available memory was full of zeroes.
Pollute free memory to increase the chance of detecting data leak.

Signed-off-by: Martin Doucha <mdoucha@suse.cz>
---

Changes since v1:
- Split patch
- Use tst_pollute_memory() instead of allocating and pre-polluting
  a fixed-size block of memory in setup().

 testcases/kernel/syscalls/ioctl/ioctl_sg01.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/testcases/kernel/syscalls/ioctl/ioctl_sg01.c b/testcases/kernel/syscalls/ioctl/ioctl_sg01.c
index daaa96be5..8c9fd0dae 100644
--- a/testcases/kernel/syscalls/ioctl/ioctl_sg01.c
+++ b/testcases/kernel/syscalls/ioctl/ioctl_sg01.c
@@ -7,9 +7,7 @@
  * CVE-2018-1000204
  *
  * Test ioctl(SG_IO) and check that kernel doesn't leak data. Requires
- * a read-accessible SCSI-compatible device (e.g. SATA disk). Running oom*
- * test program before this one may increase the chance of successfully
- * reproducing the bug.
+ * a read-accessible generic SCSI device (e.g. a DVD drive).
  *
  * Leak fixed in:
  *
@@ -29,8 +27,9 @@
 #include <sys/ioctl.h>
 #include <stdio.h>
 #include "tst_test.h"
+#include "tst_memutils.h"
 
-#define BUF_SIZE 128 * 4096
+#define BUF_SIZE (128 * 4096)
 #define CMD_SIZE 6
 
 static int devfd = -1;
@@ -80,6 +79,10 @@ static void setup(void)
 		tst_brk(TCONF, "Could not find any usable SCSI device");
 
 	tst_res(TINFO, "Found SCSI device %s", devpath);
+
+	/* Pollute some memory to avoid false negatives */
+	tst_pollute_memory(0, 0x42);
+
 	devfd = SAFE_OPEN(devpath, O_RDONLY);
 	query.interface_id = 'S';
 	query.dxfer_direction = SG_DXFER_FROM_DEV;
-- 
2.28.0