slab: Generify kernel pointer validation

As suggested by Linus, introduce a kern_ptr_validate() helper that does some sanity checks to make sure a pointer is a valid kernel pointer. This is a preparational step for fixing SLUB kmem_ptr_validate(). Cc: Andrew Morton <[email protected]> Cc: Christoph Lameter <[email protected]> Cc: David Rientjes <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Matt Mackall <[email protected]> Cc: Nick Piggin <[email protected]> Signed-off-by: Pekka Enberg <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
ckolivas · Apr 9, 2010 · fc1c183 · fc1c183
1 parent 4dc86ae
commit fc1c183
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Showing 3 changed files with 23 additions and 12 deletions.
diff --git a/include/linux/slab.h b/include/linux/slab.h
@@ -106,6 +106,7 @@ int kmem_cache_shrink(struct kmem_cache *);
 void kmem_cache_free(struct kmem_cache *, void *);
 unsigned int kmem_cache_size(struct kmem_cache *);
 const char *kmem_cache_name(struct kmem_cache *);
+int kern_ptr_validate(const void *ptr, unsigned long size);
 int kmem_ptr_validate(struct kmem_cache *cachep, const void *ptr);
 
 /*

diff --git a/mm/slab.c b/mm/slab.c
@@ -3602,21 +3602,10 @@ EXPORT_SYMBOL(kmem_cache_alloc_notrace);
  */
 int kmem_ptr_validate(struct kmem_cache *cachep, const void *ptr)
 {
-	unsigned long addr = (unsigned long)ptr;
-	unsigned long min_addr = PAGE_OFFSET;
-	unsigned long align_mask = BYTES_PER_WORD - 1;
 	unsigned long size = cachep->buffer_size;
 	struct page *page;
 
-	if (unlikely(addr < min_addr))
-		goto out;
-	if (unlikely(addr > (unsigned long)high_memory - size))
-		goto out;
-	if (unlikely(addr & align_mask))
-		goto out;
-	if (unlikely(!kern_addr_valid(addr)))
-		goto out;
-	if (unlikely(!kern_addr_valid(addr + size - 1)))
+	if (unlikely(!kern_ptr_validate(ptr, size)))
 		goto out;
 	page = virt_to_page(ptr);
 	if (unlikely(!PageSlab(page)))

diff --git a/mm/util.c b/mm/util.c
@@ -186,6 +186,27 @@ void kzfree(const void *p)
 }
 EXPORT_SYMBOL(kzfree);
 
+int kern_ptr_validate(const void *ptr, unsigned long size)
+{
+	unsigned long addr = (unsigned long)ptr;
+	unsigned long min_addr = PAGE_OFFSET;
+	unsigned long align_mask = sizeof(void *) - 1;
+
+	if (unlikely(addr < min_addr))
+		goto out;
+	if (unlikely(addr > (unsigned long)high_memory - size))
+		goto out;
+	if (unlikely(addr & align_mask))
+		goto out;
+	if (unlikely(!kern_addr_valid(addr)))
+		goto out;
+	if (unlikely(!kern_addr_valid(addr + size - 1)))
+		goto out;
+	return 1;
+out:
+	return 0;
+}
+
 /*
  * strndup_user - duplicate an existing string from user space
  * @s: The string to duplicate