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>

diff --git a/drivers/misc/lkdtm/usercopy.c b/drivers/misc/lkdtm/usercopy.c
index 945806d..6215ec9 100644 (file)
--- a/drivers/misc/lkdtm/usercopy.c
+++ b/drivers/misc/lkdtm/usercopy.c
@@ -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 @@ free_user:
        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),
 };