[PATCH v2 05/10] mm, kfence: insert KFENCE hooks for SLUB

Marco Elver
2020-09-15T13:21:26Z

From: Alexander Potapenko <glider@google.com>

Inserts KFENCE hooks into the SLUB allocator.

We note the addition of the 'orig_size' argument to slab_alloc*()
functions, to be able to pass the originally requested size to KFENCE.
When KFENCE is disabled, there is no additional overhead, since these
functions are __always_inline.

Co-developed-by: Marco Elver <elver@google.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Alexander Potapenko <glider@google.com>
---
mm/slub.c | 72 ++++++++++++++++++++++++++++++++++++++++---------------
1 file changed, 53 insertions(+), 19 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index d4177aecedf6..5c5a13a7857c 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -27,6 +27,7 @@
#include <linux/ctype.h>
#include <linux/debugobjects.h>
#include <linux/kallsyms.h>
+#include <linux/kfence.h>
#include <linux/memory.h>
#include <linux/math64.h>
#include <linux/fault-inject.h>
@@ -1557,6 +1558,11 @@ static inline bool slab_free_freelist_hook(struct kmem_cache *s,
void *old_tail = *tail ? *tail : *head;
int rsize;

+ if (is_kfence_address(next)) {
+ slab_free_hook(s, next);
+ return true;
+ }
+
/* Head and tail of the reconstructed freelist */
*head = NULL;
*tail = NULL;
@@ -2660,7 +2666,8 @@ static inline void *get_freelist(struct kmem_cache *s, struct page *page)
* already disabled (which is the case for bulk allocation).
*/
static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
- unsigned long addr, struct kmem_cache_cpu *c)
+ unsigned long addr, struct kmem_cache_cpu *c,
+ size_t orig_size)
{
void *freelist;
struct page *page;
@@ -2763,7 +2770,8 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
* cpu changes by refetching the per cpu area pointer.
*/
static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
- unsigned long addr, struct kmem_cache_cpu *c)
+ unsigned long addr, struct kmem_cache_cpu *c,
+ size_t orig_size)
{
void *p;
unsigned long flags;
@@ -2778,7 +2786,7 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
c = this_cpu_ptr(s->cpu_slab);
#endif

- p = ___slab_alloc(s, gfpflags, node, addr, c);
+ p = ___slab_alloc(s, gfpflags, node, addr, c, orig_size);
local_irq_restore(flags);
return p;
}
@@ -2805,7 +2813,7 @@ static __always_inline void maybe_wipe_obj_freeptr(struct kmem_cache *s,
* Otherwise we can simply pick the next object from the lockless free list.
*/
static __always_inline void *slab_alloc_node(struct kmem_cache *s,
- gfp_t gfpflags, int node, unsigned long addr)
+ gfp_t gfpflags, int node, unsigned long addr, size_t orig_size)
{
void *object;
struct kmem_cache_cpu *c;
@@ -2816,6 +2824,11 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s,
s = slab_pre_alloc_hook(s, &objcg, 1, gfpflags);
if (!s)
return NULL;
+
+ object = kfence_alloc(s, orig_size, gfpflags);
+ if (unlikely(object))
+ goto out;
+
redo:
/*
* Must read kmem_cache cpu data via this cpu ptr. Preemption is
@@ -2853,7 +2866,7 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s,
object = c->freelist;
page = c->page;
if (unlikely(!object || !node_match(page, node))) {
- object = __slab_alloc(s, gfpflags, node, addr, c);
+ object = __slab_alloc(s, gfpflags, node, addr, c, orig_size);
stat(s, ALLOC_SLOWPATH);
} else {
void *next_object = get_freepointer_safe(s, object);
@@ -2889,20 +2902,21 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s,
if (unlikely(slab_want_init_on_alloc(gfpflags, s)) && object)
memset(object, 0, s->object_size);

+out:
slab_post_alloc_hook(s, objcg, gfpflags, 1, &object);

return object;
}

static __always_inline void *slab_alloc(struct kmem_cache *s,
- gfp_t gfpflags, unsigned long addr)
+ gfp_t gfpflags, unsigned long addr, size_t orig_size)
{
- return slab_alloc_node(s, gfpflags, NUMA_NO_NODE, addr);
+ return slab_alloc_node(s, gfpflags, NUMA_NO_NODE, addr, orig_size);
}

void *kmem_cache_alloc(struct kmem_cache *s, gfp_t gfpflags)
{
- void *ret = slab_alloc(s, gfpflags, _RET_IP_);
+ void *ret = slab_alloc(s, gfpflags, _RET_IP_, s->object_size);

trace_kmem_cache_alloc(_RET_IP_, ret, s->object_size,
s->size, gfpflags);
@@ -2914,7 +2928,7 @@ EXPORT_SYMBOL(kmem_cache_alloc);
#ifdef CONFIG_TRACING
void *kmem_cache_alloc_trace(struct kmem_cache *s, gfp_t gfpflags, size_t size)
{
- void *ret = slab_alloc(s, gfpflags, _RET_IP_);
+ void *ret = slab_alloc(s, gfpflags, _RET_IP_, size);
trace_kmalloc(_RET_IP_, ret, size, s->size, gfpflags);
ret = kasan_kmalloc(s, ret, size, gfpflags);
return ret;
@@ -2925,7 +2939,7 @@ EXPORT_SYMBOL(kmem_cache_alloc_trace);
#ifdef CONFIG_NUMA
void *kmem_cache_alloc_node(struct kmem_cache *s, gfp_t gfpflags, int node)
{
- void *ret = slab_alloc_node(s, gfpflags, node, _RET_IP_);
+ void *ret = slab_alloc_node(s, gfpflags, node, _RET_IP_, s->object_size);

trace_kmem_cache_alloc_node(_RET_IP_, ret,
s->object_size, s->size, gfpflags, node);
@@ -2939,7 +2953,7 @@ void *kmem_cache_alloc_node_trace(struct kmem_cache *s,
gfp_t gfpflags,
int node, size_t size)
{
- void *ret = slab_alloc_node(s, gfpflags, node, _RET_IP_);
+ void *ret = slab_alloc_node(s, gfpflags, node, _RET_IP_, size);

trace_kmalloc_node(_RET_IP_, ret,
size, s->size, gfpflags, node);
@@ -2973,6 +2987,9 @@ static void __slab_free(struct kmem_cache *s, struct page *page,

stat(s, FREE_SLOWPATH);

+ if (kfence_free(head))
+ return;
+
if (kmem_cache_debug(s) &&
!free_debug_processing(s, page, head, tail, cnt, addr))
return;
@@ -3216,6 +3233,13 @@ int build_detached_freelist(struct kmem_cache *s, size_t size,
df->s = cache_from_obj(s, object); /* Support for memcg */
}

+ if (is_kfence_address(object)) {
+ slab_free_hook(df->s, object);
+ WARN_ON(!kfence_free(object));
+ p[size] = NULL; /* mark object processed */
+ return size;
+ }
+
/* Start new detached freelist */
df->page = page;
set_freepointer(df->s, object, NULL);
@@ -3290,8 +3314,14 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
c = this_cpu_ptr(s->cpu_slab);

for (i = 0; i < size; i++) {
- void *object = c->freelist;
+ void *object = kfence_alloc(s, s->object_size, flags);

+ if (unlikely(object)) {
+ p[i] = object;
+ continue;
+ }
+
+ object = c->freelist;
if (unlikely(!object)) {
/*
* We may have removed an object from c->freelist using
@@ -3307,7 +3337,7 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
* of re-populating per CPU c->freelist
*/
p[i] = ___slab_alloc(s, flags, NUMA_NO_NODE,
- _RET_IP_, c);
+ _RET_IP_, c, size);
if (unlikely(!p[i]))
goto error;

@@ -3962,7 +3992,7 @@ void *__kmalloc(size_t size, gfp_t flags)
if (unlikely(ZERO_OR_NULL_PTR(s)))
return s;

- ret = slab_alloc(s, flags, _RET_IP_);
+ ret = slab_alloc(s, flags, _RET_IP_, size);

trace_kmalloc(_RET_IP_, ret, size, s->size, flags);

@@ -4010,7 +4040,7 @@ void *__kmalloc_node(size_t size, gfp_t flags, int node)
if (unlikely(ZERO_OR_NULL_PTR(s)))
return s;

- ret = slab_alloc_node(s, flags, node, _RET_IP_);
+ ret = slab_alloc_node(s, flags, node, _RET_IP_, size);

trace_kmalloc_node(_RET_IP_, ret, size, s->size, flags, node);

@@ -4036,6 +4066,7 @@ void __check_heap_object(const void *ptr, unsigned long n, struct page *page,
struct kmem_cache *s;
unsigned int offset;
size_t object_size;
+ bool is_kfence = is_kfence_address(ptr);

ptr = kasan_reset_tag(ptr);

@@ -4048,10 +4079,13 @@ void __check_heap_object(const void *ptr, unsigned long n, struct page *page,
to_user, 0, n);

/* Find offset within object. */
- offset = (ptr - page_address(page)) % s->size;
+ if (is_kfence)
+ offset = ptr - kfence_object_start(ptr);
+ else
+ offset = (ptr - page_address(page)) % s->size;

/* Adjust for redzone and reject if within the redzone. */
- if (kmem_cache_debug_flags(s, SLAB_RED_ZONE)) {
+ if (!is_kfence && kmem_cache_debug_flags(s, SLAB_RED_ZONE)) {
if (offset < s->red_left_pad)
usercopy_abort("SLUB object in left red zone",
s->name, to_user, offset, n);
@@ -4460,7 +4494,7 @@ void *__kmalloc_track_caller(size_t size, gfp_t gfpflags, unsigned long caller)
if (unlikely(ZERO_OR_NULL_PTR(s)))
return s;

- ret = slab_alloc(s, gfpflags, caller);
+ ret = slab_alloc(s, gfpflags, caller, size);

/* Honor the call site pointer we received. */
trace_kmalloc(caller, ret, size, s->size, gfpflags);
@@ -4491,7 +4525,7 @@ void *__kmalloc_node_track_caller(size_t size, gfp_t gfpflags,
if (unlikely(ZERO_OR_NULL_PTR(s)))
return s;

- ret = slab_alloc_node(s, gfpflags, node, caller);
+ ret = slab_alloc_node(s, gfpflags, node, caller, size);

/* Honor the call site pointer we received. */
trace_kmalloc_node(caller, ret, size, s->size, gfpflags, node);
--
2.28.0.618.gf4bc123cb7-goog