kasan, vmalloc: add vmalloc tagging for SW_TAGS

Add vmalloc tagging support to SW_TAGS KASAN.

 - __kasan_unpoison_vmalloc() now assigns a random pointer tag, poisons
   the virtual mapping accordingly, and embeds the tag into the returned
   pointer.

 - __get_vm_area_node() (used by vmalloc() and vmap()) and
   pcpu_get_vm_areas() save the tagged pointer into vm_struct->addr
   (note: not into vmap_area->addr).

   This requires putting kasan_unpoison_vmalloc() after
   setup_vmalloc_vm[_locked](); otherwise the latter will overwrite the
   tagged pointer. The tagged pointer then is naturally propagateed to
   vmalloc() and vmap().

 - vm_map_ram() returns the tagged pointer directly.

As a result of this change, vm_struct->addr is now tagged.

Enabling KASAN_VMALLOC with SW_TAGS is not yet allowed.

Link: https://lkml.kernel.org/r/4a78f3c064ce905e9070c29733aca1dd254a74f1.1643047180.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index a6d6fde..d3efb6c 100644 (file)
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -403,12 +403,13 @@ void kasan_release_vmalloc(unsigned long start, unsigned long end,
                           unsigned long free_region_start,
                           unsigned long free_region_end);
 
-void __kasan_unpoison_vmalloc(const void *start, unsigned long size);
-static __always_inline void kasan_unpoison_vmalloc(const void *start,
-                                                  unsigned long size)
+void *__kasan_unpoison_vmalloc(const void *start, unsigned long size);
+static __always_inline void *kasan_unpoison_vmalloc(const void *start,
+                                                   unsigned long size)
 {
        if (kasan_enabled())
-               __kasan_unpoison_vmalloc(start, size);
+               return __kasan_unpoison_vmalloc(start, size);
+       return (void *)start;
 }
 
 void __kasan_poison_vmalloc(const void *start, unsigned long size);
@@ -433,8 +434,11 @@ static inline void kasan_release_vmalloc(unsigned long start,
                                         unsigned long free_region_start,
                                         unsigned long free_region_end) { }
 
-static inline void kasan_unpoison_vmalloc(const void *start, unsigned long size)
-{ }
+static inline void *kasan_unpoison_vmalloc(const void *start,
+                                          unsigned long size)
+{
+       return (void *)start;
+}
 static inline void kasan_poison_vmalloc(const void *start, unsigned long size)
 { }
 

diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index 39d0b32..5a866f6 100644 (file)
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -475,12 +475,14 @@ void kasan_release_vmalloc(unsigned long start, unsigned long end,
        }
 }
 
-void __kasan_unpoison_vmalloc(const void *start, unsigned long size)
+void *__kasan_unpoison_vmalloc(const void *start, unsigned long size)
 {
        if (!is_vmalloc_or_module_addr(start))
-               return;
+               return (void *)start;
 
+       start = set_tag(start, kasan_random_tag());
        kasan_unpoison(start, size, false);
+       return (void *)start;
 }
 
 /*

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index ab0a000..1ab1f1b 100644 (file)
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2231,7 +2231,7 @@ void *vm_map_ram(struct page **pages, unsigned int count, int node)
                mem = (void *)addr;
        }
 
-       kasan_unpoison_vmalloc(mem, size);
+       mem = kasan_unpoison_vmalloc(mem, size);
 
        if (vmap_pages_range(addr, addr + size, PAGE_KERNEL,
                                pages, PAGE_SHIFT) < 0) {
@@ -2464,10 +2464,10 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
                return NULL;
        }
 
-       kasan_unpoison_vmalloc((void *)va->va_start, requested_size);
-
        setup_vmalloc_vm(area, va, flags, caller);
 
+       area->addr = kasan_unpoison_vmalloc(area->addr, requested_size);
+
        return area;
 }
 
@@ -3815,9 +3815,6 @@ retry:
        for (area = 0; area < nr_vms; area++) {
                if (kasan_populate_vmalloc(vas[area]->va_start, sizes[area]))
                        goto err_free_shadow;
-
-               kasan_unpoison_vmalloc((void *)vas[area]->va_start,
-                                      sizes[area]);
        }
 
        /* insert all vm's */
@@ -3830,6 +3827,11 @@ retry:
        }
        spin_unlock(&vmap_area_lock);
 
+       /* mark allocated areas as accessible */
+       for (area = 0; area < nr_vms; area++)
+               vms[area]->addr = kasan_unpoison_vmalloc(vms[area]->addr,
+                                                        vms[area]->size);
+
        kfree(vas);
        return vms;