kasan: clean up is_kfence_address checks

1. Do not untag addresses that are passed to is_kfence_address: it
   tolerates tagged addresses.

2. Move is_kfence_address checks from internal KASAN functions
   (kasan_poison/unpoison, etc.) to external-facing ones.

   Note that kasan_poison/unpoison are never called outside of KASAN/slab
   code anymore; the comment is wrong, so drop it.

3. Simplify/reorganize the code around the updated checks.

Link: https://lkml.kernel.org/r/1065732315ef4e141b6177d8f612232d4d5bc0ab.1703188911.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index f4255e807b742b58fb2ea043d7e919fbaf4485a1..86adf80cc11a6dbeadd7f42c3acd1002d2fde548 100644 (file)
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -79,6 +79,9 @@ EXPORT_SYMBOL(kasan_disable_current);
 
 void __kasan_unpoison_range(const void *address, size_t size)
 {
+       if (is_kfence_address(address))
+               return;
+
        kasan_unpoison(address, size, false);
 }
 
@@ -218,9 +221,6 @@ static inline bool poison_slab_object(struct kmem_cache *cache, void *object,
        tagged_object = object;
        object = kasan_reset_tag(object);
 
-       if (is_kfence_address(object))
-               return false;
-
        if (unlikely(nearest_obj(cache, virt_to_slab(object), object) != object)) {
                kasan_report_invalid_free(tagged_object, ip, KASAN_REPORT_INVALID_FREE);
                return true;
@@ -247,7 +247,12 @@ static inline bool poison_slab_object(struct kmem_cache *cache, void *object,
 bool __kasan_slab_free(struct kmem_cache *cache, void *object,
                                unsigned long ip, bool init)
 {
-       bool buggy_object = poison_slab_object(cache, object, ip, init);
+       bool buggy_object;
+
+       if (is_kfence_address(object))
+               return false;
+
+       buggy_object = poison_slab_object(cache, object, ip, init);
 
        return buggy_object ? true : kasan_quarantine_put(cache, object);
 }
@@ -359,7 +364,7 @@ void * __must_check __kasan_kmalloc(struct kmem_cache *cache, const void *object
        if (unlikely(object == NULL))
                return NULL;
 
-       if (is_kfence_address(kasan_reset_tag(object)))
+       if (is_kfence_address(object))
                return (void *)object;
 
        /* The object has already been unpoisoned by kasan_slab_alloc(). */
@@ -417,7 +422,7 @@ void * __must_check __kasan_krealloc(const void *object, size_t size, gfp_t flag
        if (unlikely(object == ZERO_SIZE_PTR))
                return (void *)object;
 
-       if (is_kfence_address(kasan_reset_tag(object)))
+       if (is_kfence_address(object))
                return (void *)object;
 
        /*
@@ -483,6 +488,9 @@ bool __kasan_mempool_poison_object(void *ptr, unsigned long ip)
                return true;
        }
 
+       if (is_kfence_address(ptr))
+               return false;
+
        slab = folio_slab(folio);
        return !poison_slab_object(slab->slab_cache, ptr, ip, false);
 }
@@ -492,9 +500,6 @@ void __kasan_mempool_unpoison_object(void *ptr, size_t size, unsigned long ip)
        struct slab *slab;
        gfp_t flags = 0; /* Might be executing under a lock. */
 
-       if (is_kfence_address(kasan_reset_tag(ptr)))
-               return;
-
        slab = virt_to_slab(ptr);
 
        /*
@@ -507,6 +512,9 @@ void __kasan_mempool_unpoison_object(void *ptr, size_t size, unsigned long ip)
                return;
        }
 
+       if (is_kfence_address(ptr))
+               return;
+
        /* Unpoison the object and save alloc info for non-kmalloc() allocations. */
        unpoison_slab_object(slab->slab_cache, ptr, size, flags);
 

diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 1c34511090d7ba66cba146a513f89fd4eb315d6b..5fbcc1b805bc6e0bec0289ec09ef3a476cd397d6 100644 (file)
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -466,35 +466,23 @@ static inline u8 kasan_random_tag(void) { return 0; }
 
 static inline void kasan_poison(const void *addr, size_t size, u8 value, bool init)
 {
-       addr = kasan_reset_tag(addr);
-
-       /* Skip KFENCE memory if called explicitly outside of sl*b. */
-       if (is_kfence_address(addr))
-               return;
-
        if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK))
                return;
        if (WARN_ON(size & KASAN_GRANULE_MASK))
                return;
 
-       hw_set_mem_tag_range((void *)addr, size, value, init);
+       hw_set_mem_tag_range(kasan_reset_tag(addr), size, value, init);
 }
 
 static inline void kasan_unpoison(const void *addr, size_t size, bool init)
 {
        u8 tag = get_tag(addr);
 
-       addr = kasan_reset_tag(addr);
-
-       /* Skip KFENCE memory if called explicitly outside of sl*b. */
-       if (is_kfence_address(addr))
-               return;
-
        if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK))
                return;
        size = round_up(size, KASAN_GRANULE_SIZE);
 
-       hw_set_mem_tag_range((void *)addr, size, tag, init);
+       hw_set_mem_tag_range(kasan_reset_tag(addr), size, tag, init);
 }
 
 static inline bool kasan_byte_accessible(const void *addr)

diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index 0154d200be40368ff06451dc5da72dcdf1ef61f2..30625303d01a3025ecda10b53357ae7cfafc51d4 100644 (file)
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -135,10 +135,6 @@ void kasan_poison(const void *addr, size_t size, u8 value, bool init)
         */
        addr = kasan_reset_tag(addr);
 
-       /* Skip KFENCE memory if called explicitly outside of sl*b. */
-       if (is_kfence_address(addr))
-               return;
-
        if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK))
                return;
        if (WARN_ON(size & KASAN_GRANULE_MASK))
@@ -175,14 +171,6 @@ void kasan_unpoison(const void *addr, size_t size, bool init)
         */
        addr = kasan_reset_tag(addr);
 
-       /*
-        * Skip KFENCE memory if called explicitly outside of sl*b. Also note
-        * that calls to ksize(), where size is not a multiple of machine-word
-        * size, would otherwise poison the invalid portion of the word.
-        */
-       if (is_kfence_address(addr))
-               return;
-
        if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK))
                return;