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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: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook 2022-05-12 10:19:41 -07:00
parent d2b8060f16
commit fc34eec686
1 changed files with 83 additions and 0 deletions
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83
drivers/misc/lkdtm/usercopy.c
View File

@ -5,6 +5,7 @@
*/ */
#include "lkdtm.h" #include "lkdtm.h"
#include <linux/slab.h> #include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/vmalloc.h> #include <linux/vmalloc.h>
#include <linux/sched/task_stack.h> #include <linux/sched/task_stack.h>
#include <linux/mman.h> #include <linux/mman.h>
@ -341,6 +342,86 @@ free_user:
vm_munmap(user_addr, PAGE_SIZE); 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) void __init lkdtm_usercopy_init(void)
{ {
/* Prepare cache that lacks SLAB_USERCOPY flag. */ /* Prepare cache that lacks SLAB_USERCOPY flag. */
@ -365,6 +446,8 @@ static struct crashtype crashtypes[] = {
CRASHTYPE(USERCOPY_STACK_FRAME_TO), CRASHTYPE(USERCOPY_STACK_FRAME_TO),
CRASHTYPE(USERCOPY_STACK_FRAME_FROM), CRASHTYPE(USERCOPY_STACK_FRAME_FROM),
CRASHTYPE(USERCOPY_STACK_BEYOND), CRASHTYPE(USERCOPY_STACK_BEYOND),
CRASHTYPE(USERCOPY_VMALLOC),
CRASHTYPE(USERCOPY_FOLIO),
CRASHTYPE(USERCOPY_KERNEL), CRASHTYPE(USERCOPY_KERNEL),
}; };