lkdtm: Add tests for NULL pointer dereference

[ Upstream commit 59a1220 ] Introduce lkdtm tests for NULL pointer dereference: check access or exec at NULL address, since these errors tend to be reported differently from the general fault error text. For example from x86: pr_alert("BUG: unable to handle kernel %s at %px\n", address < PAGE_SIZE ? "NULL pointer dereference" : "paging request", (void *)address); Signed-off-by: Christophe Leroy <[email protected]> Signed-off-by: Kees Cook <[email protected]> Signed-off-by: Sasha Levin <[email protected]>
platipus25 · Apr 20, 2019 · f2778b3 · f2778b3
1 parent b035faf
commit f2778b3
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diff --git a/drivers/misc/lkdtm.h b/drivers/misc/lkdtm.h
@@ -45,7 +45,9 @@ void lkdtm_EXEC_KMALLOC(void);
 void lkdtm_EXEC_VMALLOC(void);
 void lkdtm_EXEC_RODATA(void);
 void lkdtm_EXEC_USERSPACE(void);
+void lkdtm_EXEC_NULL(void);
 void lkdtm_ACCESS_USERSPACE(void);
+void lkdtm_ACCESS_NULL(void);
 
 /* lkdtm_refcount.c */
 void lkdtm_REFCOUNT_INC_OVERFLOW(void);

diff --git a/drivers/misc/lkdtm_core.c b/drivers/misc/lkdtm_core.c
@@ -220,7 +220,9 @@ struct crashtype crashtypes[] = {
 	CRASHTYPE(EXEC_VMALLOC),
 	CRASHTYPE(EXEC_RODATA),
 	CRASHTYPE(EXEC_USERSPACE),
+	CRASHTYPE(EXEC_NULL),
 	CRASHTYPE(ACCESS_USERSPACE),
+	CRASHTYPE(ACCESS_NULL),
 	CRASHTYPE(WRITE_RO),
 	CRASHTYPE(WRITE_RO_AFTER_INIT),
 	CRASHTYPE(WRITE_KERN),

diff --git a/drivers/misc/lkdtm_perms.c b/drivers/misc/lkdtm_perms.c
@@ -164,6 +164,11 @@ void lkdtm_EXEC_USERSPACE(void)
 	vm_munmap(user_addr, PAGE_SIZE);
 }
 
+void lkdtm_EXEC_NULL(void)
+{
+	execute_location(NULL, CODE_AS_IS);
+}
+
 void lkdtm_ACCESS_USERSPACE(void)
 {
 	unsigned long user_addr, tmp = 0;
@@ -195,6 +200,19 @@ void lkdtm_ACCESS_USERSPACE(void)
 	vm_munmap(user_addr, PAGE_SIZE);
 }
 
+void lkdtm_ACCESS_NULL(void)
+{
+	unsigned long tmp;
+	unsigned long *ptr = (unsigned long *)NULL;
+
+	pr_info("attempting bad read at %px\n", ptr);
+	tmp = *ptr;
+	tmp += 0xc0dec0de;
+
+	pr_info("attempting bad write at %px\n", ptr);
+	*ptr = tmp;
+}
+
 void __init lkdtm_perms_init(void)
 {
 	/* Make sure we can write to __ro_after_init values during __init */