Commit fc34eec6 authored by Kees Cook's avatar Kees Cook
Browse files

lkdtm/usercopy: Check vmalloc and >0-order folios 



Add coverage for the recently added usercopy checks for vmalloc and
folios, via USERCOPY_VMALLOC and USERCOPY_FOLIO respectively.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent d2b8060f

drivers/misc/lkdtm/usercopy.c

+83 −0
Original line number Diff line number Diff line
@@ -5,6 +5,7 @@ 
 */

#include "lkdtm.h"

#include <linux/slab.h>

#include <linux/highmem.h>

#include <linux/vmalloc.h>

#include <linux/sched/task_stack.h>

#include <linux/mman.h>
@@ -341,6 +342,86 @@ static void lkdtm_USERCOPY_KERNEL(void) 
	vm_munmap(user_addr, PAGE_SIZE);

}



/*

 * This expects "kaddr" to point to a PAGE_SIZE allocation, which means

 * a more complete test that would include copy_from_user() would risk

 * memory corruption. Just test copy_to_user() here, as that exercises

 * almost exactly the same code paths.

 */

static void do_usercopy_page_span(const char *name, void *kaddr)

{

	unsigned long uaddr;



	uaddr = vm_mmap(NULL, 0, PAGE_SIZE, PROT_READ | PROT_WRITE,

			MAP_ANONYMOUS | MAP_PRIVATE, 0);

	if (uaddr >= TASK_SIZE) {

		pr_warn("Failed to allocate user memory\n");

		return;

	}



	/* Initialize contents. */

	memset(kaddr, 0xAA, PAGE_SIZE);



	/* Bump the kaddr forward to detect a page-spanning overflow. */

	kaddr += PAGE_SIZE / 2;



	pr_info("attempting good copy_to_user() from kernel %s: %px\n",

		name, kaddr);

	if (copy_to_user((void __user *)uaddr, kaddr,

			 unconst + (PAGE_SIZE / 2))) {

		pr_err("copy_to_user() failed unexpectedly?!\n");

		goto free_user;

	}



	pr_info("attempting bad copy_to_user() from kernel %s: %px\n",

		name, kaddr);

	if (copy_to_user((void __user *)uaddr, kaddr, unconst + PAGE_SIZE)) {

		pr_warn("Good, copy_to_user() failed, but lacked Oops(?!)\n");

		goto free_user;

	}



	pr_err("FAIL: bad copy_to_user() not detected!\n");

	pr_expected_config_param(CONFIG_HARDENED_USERCOPY, "hardened_usercopy");



free_user:

	vm_munmap(uaddr, PAGE_SIZE);

}



static void lkdtm_USERCOPY_VMALLOC(void)

{

	void *addr;



	addr = vmalloc(PAGE_SIZE);

	if (!addr) {

		pr_err("vmalloc() failed!?\n");

		return;

	}

	do_usercopy_page_span("vmalloc", addr);

	vfree(addr);

}



static void lkdtm_USERCOPY_FOLIO(void)

{

	struct folio *folio;

	void *addr;



	/*

	 * FIXME: Folio checking currently misses 0-order allocations, so

	 * allocate and bump forward to the last page.

	 */

	folio = folio_alloc(GFP_KERNEL | __GFP_ZERO, 1);

	if (!folio) {

		pr_err("folio_alloc() failed!?\n");

		return;

	}

	addr = folio_address(folio);

	if (addr)

		do_usercopy_page_span("folio", addr + PAGE_SIZE);

	else

		pr_err("folio_address() failed?!\n");

	folio_put(folio);

}



void __init lkdtm_usercopy_init(void)

{

	/* Prepare cache that lacks SLAB_USERCOPY flag. */
@@ -365,6 +446,8 @@ static struct crashtype crashtypes[] = { 
	CRASHTYPE(USERCOPY_STACK_FRAME_TO),

	CRASHTYPE(USERCOPY_STACK_FRAME_FROM),

	CRASHTYPE(USERCOPY_STACK_BEYOND),

	CRASHTYPE(USERCOPY_VMALLOC),

	CRASHTYPE(USERCOPY_FOLIO),

	CRASHTYPE(USERCOPY_KERNEL),

};