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lkdtm: add "WRITE_KERN" test

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Add "WRITE_KERN" crash target to validate that kernel executable memory
is not writable.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Kees Cook 2014-02-09 13:48:48 -08:00 committed by Greg Kroah-Hartman
parent aac416fc38
commit dc2b9e9069
1 changed files with 25 additions and 0 deletions
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25
drivers/misc/lkdtm.c
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@ -102,6 +102,7 @@ enum ctype {
CT_EXEC_USERSPACE, CT_EXEC_USERSPACE,
CT_ACCESS_USERSPACE, CT_ACCESS_USERSPACE,
CT_WRITE_RO, CT_WRITE_RO,
CT_WRITE_KERN,
}; };
static char* cp_name[] = { static char* cp_name[] = {
@ -138,6 +139,7 @@ static char* cp_type[] = {
"EXEC_USERSPACE", "EXEC_USERSPACE",
"ACCESS_USERSPACE", "ACCESS_USERSPACE",
"WRITE_RO", "WRITE_RO",
"WRITE_KERN",
}; };
static struct jprobe lkdtm; static struct jprobe lkdtm;
@ -317,6 +319,13 @@ static void do_nothing(void)
return; return;
} }
/* Must immediately follow do_nothing for size calculuations to work out. */
static void do_overwritten(void)
{
pr_info("do_overwritten wasn't overwritten!\n");
return;
}
static noinline void corrupt_stack(void) static noinline void corrupt_stack(void)
{ {
/* Use default char array length that triggers stack protection. */ /* Use default char array length that triggers stack protection. */
@ -496,6 +505,22 @@ static void lkdtm_do_action(enum ctype which)
break; break;
} }
case CT_WRITE_KERN: {
size_t size;
unsigned char *ptr;
size = (unsigned long)do_overwritten -
(unsigned long)do_nothing;
ptr = (unsigned char *)do_overwritten;
pr_info("attempting bad %zu byte write at %p\n", size, ptr);
memcpy(ptr, (unsigned char *)do_nothing, size);
flush_icache_range((unsigned long)ptr,
(unsigned long)(ptr + size));
do_overwritten();
break;
}
case CT_NONE: case CT_NONE:
default: default:
break; break;