Add a few padding bytes on either side of the test buffer, and check
that these (and the part of the buffer not used) are untouched by
vsnprintf.
Acked-by: Kees Cook <keesc...@chromium.org>
Signed-off-by: Rasmus Villemoes <li...@rasmusvillemoes.dk>
---
lib/test_printf.c | 24 +++++++++++++++++++-----
1 file changed, 19 insertions(+), 5 deletions(-)
diff --git a/lib/test_printf.c b/lib/test_printf.c
index 9232a2add28c..1ce1a1dd8faf 100644
--- a/lib/test_printf.c
+++ b/lib/test_printf.c
@@ -16,6 +16,7 @@
#include <linux/in.h>
#define BUF_SIZE 256
+#define PAD_SIZE 16
#define FILL_CHAR '$'
#define PTR1 ((void*)0x01234567)
@@ -39,6 +40,7 @@
static unsigned total_tests __initdata;
static unsigned failed_tests __initdata;
static char *test_buffer __initdata;
+static char *alloced_buffer __initdata;
static int __printf(4, 0) __init
do_test(int bufsize, const char *expect, int elen,
@@ -49,7 +51,7 @@ do_test(int bufsize, const char *expect, int elen,
total_tests++;
- memset(test_buffer, FILL_CHAR, BUF_SIZE);
+ memset(alloced_buffer, FILL_CHAR, BUF_SIZE + 2*PAD_SIZE);
va_copy(aq, ap);
ret = vsnprintf(test_buffer, bufsize, fmt, aq);
va_end(aq);
@@ -60,8 +62,13 @@ do_test(int bufsize, const char *expect, int elen,
return 1;
}
+ if (memchr_inv(alloced_buffer, FILL_CHAR, PAD_SIZE)) {
+ pr_warn("vsnprintf(buf, %d, \"%s\", ...) wrote before
buffer\n", bufsize, fmt);
+ return 1;
+ }
+
if (!bufsize) {
- if (memchr_inv(test_buffer, FILL_CHAR, BUF_SIZE)) {
+ if (memchr_inv(test_buffer, FILL_CHAR, BUF_SIZE + PAD_SIZE)) {
pr_warn("vsnprintf(buf, 0, \"%s\", ...) wrote to
buffer\n",
fmt);
return 1;
@@ -76,6 +83,12 @@ do_test(int bufsize, const char *expect, int elen,
return 1;
}
+ if (memchr_inv(test_buffer + written + 1, FILL_CHAR, BUF_SIZE +
PAD_SIZE - (written + 1))) {
+ pr_warn("vsnprintf(buf, %d, \"%s\", ...) wrote beyond the
nul-terminator\n",
+ bufsize, fmt);
+ return 1;
+ }
+
if (memcmp(test_buffer, expect, written)) {
pr_warn("vsnprintf(buf, %d, \"%s\", ...) wrote '%s', expected
'%.*s'\n",
bufsize, fmt, test_buffer, written, expect);
@@ -342,16 +355,17 @@ test_pointer(void)
static int __init
test_printf_init(void)
{
- test_buffer = kmalloc(BUF_SIZE, GFP_KERNEL);
- if (!test_buffer)
+ alloced_buffer = kmalloc(BUF_SIZE + 2*PAD_SIZE, GFP_KERNEL);
+ if (!alloced_buffer)
return -ENOMEM;
+ test_buffer = alloced_buffer + PAD_SIZE;
test_basic();
test_number();
test_string();
test_pointer();
- kfree(test_buffer);
+ kfree(alloced_buffer);
if (failed_tests == 0)
pr_info("all %u tests passed\n", total_tests);
--
2.6.1
--
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