Commit 59a12205 authored by Christophe Leroy's avatar Christophe Leroy Committed by Kees Cook
Browse files

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: default avatarChristophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent 4c411157

drivers/misc/lkdtm/core.c

+2 −0
Original line number Diff line number Diff line
@@ -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),

drivers/misc/lkdtm/lkdtm.h

+2 −0
Original line number Diff line number Diff line
@@ -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);

drivers/misc/lkdtm/perms.c

+18 −0
Original line number Diff line number Diff line
@@ -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 */

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