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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>
This commit is contained in:
Christophe Leroy 2018-12-14 15:26:20 +00:00 committed by Kees Cook
parent 4c411157a4
commit 59a12205d3
3 changed files with 22 additions and 0 deletions
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2
drivers/misc/lkdtm/core.c
View File

@ -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),

2
drivers/misc/lkdtm/lkdtm.h
View File

@ -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);

18
drivers/misc/lkdtm/perms.c
View File

@ -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 */