lkdtm: Add tests for NULL pointer dereference
[ Upstream commit 59a12205d3c32aee4c13ca36889fdf7cfed31126 ]
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 <christophe.leroy@c-s.fr>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
diff --git a/drivers/misc/lkdtm_perms.c b/drivers/misc/lkdtm_perms.c
index 45f1c0f..1a9dcda 100644
--- a/drivers/misc/lkdtm_perms.c
+++ b/drivers/misc/lkdtm_perms.c
@@ -160,6 +160,11 @@
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;
@@ -191,6 +196,19 @@
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 */