@@ -16,6 +16,7 @@
#include <linux/vmalloc.h>
struct page;
+struct kmem_cache;
#ifdef CONFIG_KMSAN
@@ -73,6 +74,44 @@ void kmsan_free_page(struct page *page, unsigned int order);
*/
void kmsan_copy_page_meta(struct page *dst, struct page *src);
+/**
+ * kmsan_slab_alloc() - Notify KMSAN about a slab allocation.
+ * @s: slab cache the object belongs to.
+ * @object: object pointer.
+ * @flags: GFP flags passed to the allocator.
+ *
+ * Depending on cache flags and GFP flags, KMSAN sets up the metadata of the
+ * newly created object, marking it as initialized or uninitialized.
+ */
+void kmsan_slab_alloc(struct kmem_cache *s, void *object, gfp_t flags);
+
+/**
+ * kmsan_slab_free() - Notify KMSAN about a slab deallocation.
+ * @s: slab cache the object belongs to.
+ * @object: object pointer.
+ *
+ * KMSAN marks the freed object as uninitialized.
+ */
+void kmsan_slab_free(struct kmem_cache *s, void *object);
+
+/**
+ * kmsan_kmalloc_large() - Notify KMSAN about a large slab allocation.
+ * @ptr: object pointer.
+ * @size: object size.
+ * @flags: GFP flags passed to the allocator.
+ *
+ * Similar to kmsan_slab_alloc(), but for large allocations.
+ */
+void kmsan_kmalloc_large(const void *ptr, size_t size, gfp_t flags);
+
+/**
+ * kmsan_kfree_large() - Notify KMSAN about a large slab deallocation.
+ * @ptr: object pointer.
+ *
+ * Similar to kmsan_slab_free(), but for large allocations.
+ */
+void kmsan_kfree_large(const void *ptr);
+
/**
* kmsan_map_kernel_range_noflush() - Notify KMSAN about a vmap.
* @start: start of vmapped range.
@@ -139,6 +178,24 @@ static inline void kmsan_copy_page_meta(struct page *dst, struct page *src)
{
}
+static inline void kmsan_slab_alloc(struct kmem_cache *s, void *object,
+ gfp_t flags)
+{
+}
+
+static inline void kmsan_slab_free(struct kmem_cache *s, void *object)
+{
+}
+
+static inline void kmsan_kmalloc_large(const void *ptr, size_t size,
+ gfp_t flags)
+{
+}
+
+static inline void kmsan_kfree_large(const void *ptr)
+{
+}
+
static inline void kmsan_vmap_pages_range_noflush(unsigned long start,
unsigned long end,
pgprot_t prot,
@@ -26,6 +26,86 @@
* skipping effects of functions like memset() inside instrumented code.
*/
+void kmsan_slab_alloc(struct kmem_cache *s, void *object, gfp_t flags)
+{
+ if (unlikely(object == NULL))
+ return;
+ if (!kmsan_enabled || kmsan_in_runtime())
+ return;
+ /*
+ * There's a ctor or this is an RCU cache - do nothing. The memory
+ * status hasn't changed since last use.
+ */
+ if (s->ctor || (s->flags & SLAB_TYPESAFE_BY_RCU))
+ return;
+
+ kmsan_enter_runtime();
+ if (flags & __GFP_ZERO)
+ kmsan_internal_unpoison_memory(object, s->object_size,
+ KMSAN_POISON_CHECK);
+ else
+ kmsan_internal_poison_memory(object, s->object_size, flags,
+ KMSAN_POISON_CHECK);
+ kmsan_leave_runtime();
+}
+EXPORT_SYMBOL(kmsan_slab_alloc);
+
+void kmsan_slab_free(struct kmem_cache *s, void *object)
+{
+ if (!kmsan_enabled || kmsan_in_runtime())
+ return;
+
+ /* RCU slabs could be legally used after free within the RCU period */
+ if (unlikely(s->flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)))
+ return;
+ /*
+ * If there's a constructor, freed memory must remain in the same state
+ * until the next allocation. We cannot save its state to detect
+ * use-after-free bugs, instead we just keep it unpoisoned.
+ */
+ if (s->ctor)
+ return;
+ kmsan_enter_runtime();
+ kmsan_internal_poison_memory(object, s->object_size, GFP_KERNEL,
+ KMSAN_POISON_CHECK | KMSAN_POISON_FREE);
+ kmsan_leave_runtime();
+}
+EXPORT_SYMBOL(kmsan_slab_free);
+
+void kmsan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
+{
+ if (unlikely(ptr == NULL))
+ return;
+ if (!kmsan_enabled || kmsan_in_runtime())
+ return;
+ kmsan_enter_runtime();
+ if (flags & __GFP_ZERO)
+ kmsan_internal_unpoison_memory((void *)ptr, size,
+ /*checked*/ true);
+ else
+ kmsan_internal_poison_memory((void *)ptr, size, flags,
+ KMSAN_POISON_CHECK);
+ kmsan_leave_runtime();
+}
+EXPORT_SYMBOL(kmsan_kmalloc_large);
+
+void kmsan_kfree_large(const void *ptr)
+{
+ struct page *page;
+
+ if (!kmsan_enabled || kmsan_in_runtime())
+ return;
+ kmsan_enter_runtime();
+ page = virt_to_head_page((void *)ptr);
+ KMSAN_WARN_ON(ptr != page_address(page));
+ kmsan_internal_poison_memory((void *)ptr,
+ PAGE_SIZE << compound_order(page),
+ GFP_KERNEL,
+ KMSAN_POISON_CHECK | KMSAN_POISON_FREE);
+ kmsan_leave_runtime();
+}
+EXPORT_SYMBOL(kmsan_kfree_large);
+
static unsigned long vmalloc_shadow(unsigned long addr)
{
return (unsigned long)kmsan_get_metadata((void *)addr,
@@ -734,6 +734,7 @@ static inline void slab_post_alloc_hook(struct kmem_cache *s,
memset(p[i], 0, s->object_size);
kmemleak_alloc_recursive(p[i], s->object_size, 1,
s->flags, flags);
+ kmsan_slab_alloc(s, p[i], flags);
}
memcg_slab_post_alloc_hook(s, objcg, flags, size, p);
@@ -22,6 +22,7 @@
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/kasan.h>
+#include <linux/kmsan.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/mempolicy.h>
@@ -357,18 +358,28 @@ static void prefetch_freepointer(const struct kmem_cache *s, void *object)
prefetchw(object + s->offset);
}
+/*
+ * When running under KMSAN, get_freepointer_safe() may return an uninitialized
+ * pointer value in the case the current thread loses the race for the next
+ * memory chunk in the freelist. In that case this_cpu_cmpxchg_double() in
+ * slab_alloc_node() will fail, so the uninitialized value won't be used, but
+ * KMSAN will still check all arguments of cmpxchg because of imperfect
+ * handling of inline assembly.
+ * To work around this problem, use kmsan_init() to force initialize the
+ * return value of get_freepointer_safe().
+ */
static inline void *get_freepointer_safe(struct kmem_cache *s, void *object)
{
unsigned long freepointer_addr;
void *p;
if (!debug_pagealloc_enabled_static())
- return get_freepointer(s, object);
+ return kmsan_init(get_freepointer(s, object));
object = kasan_reset_tag(object);
freepointer_addr = (unsigned long)object + s->offset;
copy_from_kernel_nofault(&p, (void **)freepointer_addr, sizeof(p));
- return freelist_ptr(s, p, freepointer_addr);
+ return kmsan_init(freelist_ptr(s, p, freepointer_addr));
}
static inline void set_freepointer(struct kmem_cache *s, void *object, void *fp)
@@ -1683,6 +1694,7 @@ static inline void *kmalloc_large_node_hook(void *ptr, size_t size, gfp_t flags)
ptr = kasan_kmalloc_large(ptr, size, flags);
/* As ptr might get tagged, call kmemleak hook after KASAN. */
kmemleak_alloc(ptr, size, 1, flags);
+ kmsan_kmalloc_large(ptr, size, flags);
return ptr;
}
@@ -1690,12 +1702,14 @@ static __always_inline void kfree_hook(void *x)
{
kmemleak_free(x);
kasan_kfree_large(x);
+ kmsan_kfree_large(x);
}
static __always_inline bool slab_free_hook(struct kmem_cache *s,
void *x, bool init)
{
kmemleak_free_recursive(x, s->flags);
+ kmsan_slab_free(s, x);
debug_check_no_locks_freed(x, s->object_size);
@@ -3729,6 +3743,7 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
*/
slab_post_alloc_hook(s, objcg, flags, size, p,
slab_want_init_on_alloc(flags, s));
+
return i;
error:
slub_put_cpu_ptr(s->cpu_slab);
@@ -5910,6 +5925,7 @@ static char *create_unique_id(struct kmem_cache *s)
p += sprintf(p, "%07u", s->size);
BUG_ON(p > name + ID_STR_LENGTH - 1);
+ kmsan_unpoison_memory(name, p - name);
return name;
}
@@ -6011,6 +6027,7 @@ static int sysfs_slab_alias(struct kmem_cache *s, const char *name)
al->name = name;
al->next = alias_list;
alias_list = al;
+ kmsan_unpoison_memory(al, sizeof(struct saved_alias));
return 0;
}
In order to report uninitialized memory coming from heap allocations KMSAN has to poison them unless they're created with __GFP_ZERO. It's handy that we need KMSAN hooks in the places where init_on_alloc/init_on_free initialization is performed. Signed-off-by: Alexander Potapenko <glider@google.com> --- v2: -- move the implementation of SLUB hooks here Link: https://linux-review.googlesource.com/id/I6954b386c5c5d7f99f48bb6cbcc74b75136ce86e --- include/linux/kmsan.h | 57 ++++++++++++++++++++++++++++++ mm/kmsan/hooks.c | 80 +++++++++++++++++++++++++++++++++++++++++++ mm/slab.h | 1 + mm/slub.c | 21 ++++++++++-- 4 files changed, 157 insertions(+), 2 deletions(-)