From: Christophe Leroy <christophe.leroy@c-s.fr>
Date: Fri, 14 Dec 2018 15:26:20 +0000 (+0000)
Subject: lkdtm: Add tests for NULL pointer dereference
X-Git-Tag: v5.1-rc1~147^2~177^2
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=59a12205d3c32aee4c13ca36889fdf7cfed31126;p=linux.git

lkdtm: Add tests for NULL pointer dereference

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>
---

diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
index 5d41c2230d2e..c09133ac9803 100644
--- a/drivers/misc/lkdtm/core.c
+++ b/drivers/misc/lkdtm/core.c
@@ -143,7 +143,9 @@ static const 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/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
index 3c6fd327e166..b69ee004a3f7 100644
--- a/drivers/misc/lkdtm/lkdtm.h
+++ b/drivers/misc/lkdtm/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/perms.c b/drivers/misc/lkdtm/perms.c
index fa54add6375a..62f76d506f04 100644
--- 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 */