[160/166] drivers/misc/lkdtm/bugs.c: add arithmetic overflow and array bounds checks

Commit Message

Andrew Morton April 7, 2020, 3:12 a.m. UTC

From: Kees Cook <[e-mail]>
Subject: drivers/misc/lkdtm/bugs.c: add arithmetic overflow and array bounds checks

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

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Kees Cook <[e-mail]>
Acked-by: Dmitry Vyukov <[e-mail]>
Cc: Alexander Potapenko <[e-mail]>
Cc: Andrey Konovalov <[e-mail]>
Cc: Andrey Ryabinin <[e-mail]>
Cc: Ard Biesheuvel <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Cc: Dan Carpenter <[e-mail]>
Cc: Elena Petrova <[e-mail]>
Cc: "Gustavo A. R. Silva" <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 drivers/misc/lkdtm/bugs.c  |   75 +++++++++++++++++++++++++++++++++++
 drivers/misc/lkdtm/core.c  |    3 +
 drivers/misc/lkdtm/lkdtm.h |    3 +
 3 files changed, 81 insertions(+)

Patch

--- a/drivers/misc/lkdtm/bugs.c~lkdtm-bugs-add-arithmetic-overflow-and-array-bounds-checks
+++ a/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)
 {
 	/*
--- a/drivers/misc/lkdtm/core.c~lkdtm-bugs-add-arithmetic-overflow-and-array-bounds-checks
+++ a/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),
--- a/drivers/misc/lkdtm/lkdtm.h~lkdtm-bugs-add-arithmetic-overflow-and-array-bounds-checks
+++ a/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);