drivers/misc/lkdtm/bugs.c: add arithmetic overflow and array bounds c…

…hecks

Adds LKDTM tests for arithmetic overflow (both signed and unsigned), as
well as array bounds checking.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Elena Petrova <lenaptr@google.com>
Cc: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Link: http://lkml.kernel.org/r/20200227193516.32566-4-keescook@chromium.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/misc/lkdtm/bugs.c

@@ -11,6 +11,7 @@
 #include <linux/sched/signal.h>
 #include <linux/sched/task_stack.h>
 #include <linux/uaccess.h>
+#include <linux/slab.h>
 
 #ifdef CONFIG_X86_32
 #include <asm/desc.h>
@@ -175,6 +176,80 @@ void lkdtm_HUNG_TASK(void)
 	schedule();
 }
 
+volatile unsigned int huge = INT_MAX - 2;
+volatile unsigned int ignored;
+
+void lkdtm_OVERFLOW_SIGNED(void)
+{
+	int value;
+
+	value = huge;
+	pr_info("Normal signed addition ...\n");
+	value += 1;
+	ignored = value;
+
+	pr_info("Overflowing signed addition ...\n");
+	value += 4;
+	ignored = value;
+}
+
+
+void lkdtm_OVERFLOW_UNSIGNED(void)
+{
+	unsigned int value;
+
+	value = huge;
+	pr_info("Normal unsigned addition ...\n");
+	value += 1;
+	ignored = value;
+
+	pr_info("Overflowing unsigned addition ...\n");
+	value += 4;
+	ignored = value;
+}
+
+/* Intentially using old-style flex array definition of 1 byte. */
+struct array_bounds_flex_array {
+	int one;
+	int two;
+	char data[1];
+};
+
+struct array_bounds {
+	int one;
+	int two;
+	char data[8];
+	int three;
+};
+
+void lkdtm_ARRAY_BOUNDS(void)
+{
+	struct array_bounds_flex_array *not_checked;
+	struct array_bounds *checked;
+	volatile int i;
+
+	not_checked = kmalloc(sizeof(*not_checked) * 2, GFP_KERNEL);
+	checked = kmalloc(sizeof(*checked) * 2, GFP_KERNEL);
+
+	pr_info("Array access within bounds ...\n");
+	/* For both, touch all bytes in the actual member size. */
+	for (i = 0; i < sizeof(checked->data); i++)
+		checked->data[i] = 'A';
+	/*
+	 * For the uninstrumented flex array member, also touch 1 byte
+	 * beyond to verify it is correctly uninstrumented.
+	 */
+	for (i = 0; i < sizeof(not_checked->data) + 1; i++)
+		not_checked->data[i] = 'A';
+
+	pr_info("Array access beyond bounds ...\n");
+	for (i = 0; i < sizeof(checked->data) + 1; i++)
+		checked->data[i] = 'B';
+
+	kfree(not_checked);
+	kfree(checked);
+}
+
 void lkdtm_CORRUPT_LIST_ADD(void)
 {
 	/*

drivers/misc/lkdtm/core.c

@@ -130,6 +130,9 @@ static const struct crashtype crashtypes[] = {
 	CRASHTYPE(HARDLOCKUP),
 	CRASHTYPE(SPINLOCKUP),
 	CRASHTYPE(HUNG_TASK),
+	CRASHTYPE(OVERFLOW_SIGNED),
+	CRASHTYPE(OVERFLOW_UNSIGNED),
+	CRASHTYPE(ARRAY_BOUNDS),
 	CRASHTYPE(EXEC_DATA),
 	CRASHTYPE(EXEC_STACK),
 	CRASHTYPE(EXEC_KMALLOC),

drivers/misc/lkdtm/lkdtm.h

@@ -22,6 +22,9 @@ void lkdtm_SOFTLOCKUP(void);
 void lkdtm_HARDLOCKUP(void);
 void lkdtm_SPINLOCKUP(void);
 void lkdtm_HUNG_TASK(void);
+void lkdtm_OVERFLOW_SIGNED(void);
+void lkdtm_OVERFLOW_UNSIGNED(void);
+void lkdtm_ARRAY_BOUNDS(void);
 void lkdtm_CORRUPT_LIST_ADD(void);
 void lkdtm_CORRUPT_LIST_DEL(void);
 void lkdtm_CORRUPT_USER_DS(void);