Merge tag 'slab-for-6.9-rc7-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab

Pull slab fixes from Vlastimil Babka:

 - Fix for cleanup infrastructure (Dan Carpenter)

   This makes the __free(kfree) cleanup hooks not crash on error
   pointers.

 - SLUB fix for freepointer checking (Nicolas Bouchinet)

   This fixes a recently introduced bug that manifests when
   init_on_free, CONFIG_SLAB_FREELIST_HARDENED and consistency checks
   (slub_debug=F) are all enabled, and results in false-positive
   freepointer corrupt reports for caches that store freepointer outside
   of the object area.

* tag 'slab-for-6.9-rc7-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab:
  mm/slab: make __free(kfree) accept error pointers
  mm/slub: avoid zeroing outside-object freepointer for single free

2 files changed, 31 insertions, 25 deletions

diff --git a/include/linux/slab.h b/include/linux/slab.h
index e53cbfa183255..739b212625077 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -266,7 +266,7 @@ void kfree(const void *objp);
 void kfree_sensitive(const void *objp);
 size_t __ksize(const void *objp);
 
-DEFINE_FREE(kfree, void *, if (_T) kfree(_T))
+DEFINE_FREE(kfree, void *, if (!IS_ERR_OR_NULL(_T)) kfree(_T))
 
 /**
  * ksize - Report actual allocation size of associated object
@@ -792,7 +792,7 @@ static inline __alloc_size(1, 2) void *kvcalloc(size_t n, size_t size, gfp_t fla
 extern void *kvrealloc(const void *p, size_t oldsize, size_t newsize, gfp_t flags)
 		      __realloc_size(3);
 extern void kvfree(const void *addr);
-DEFINE_FREE(kvfree, void *, if (_T) kvfree(_T))
+DEFINE_FREE(kvfree, void *, if (!IS_ERR_OR_NULL(_T)) kvfree(_T))
 
 extern void kvfree_sensitive(const void *addr, size_t len);
 
diff --git a/mm/slub.c b/mm/slub.c
index 1bb2a93cf7b6a..24f702afd4584 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -557,6 +557,26 @@ static inline void set_freepointer(struct kmem_cache *s, void *object, void *fp)
 	*(freeptr_t *)freeptr_addr = freelist_ptr_encode(s, fp, freeptr_addr);
 }
 
+/*
+ * See comment in calculate_sizes().
+ */
+static inline bool freeptr_outside_object(struct kmem_cache *s)
+{
+	return s->offset >= s->inuse;
+}
+
+/*
+ * Return offset of the end of info block which is inuse + free pointer if
+ * not overlapping with object.
+ */
+static inline unsigned int get_info_end(struct kmem_cache *s)
+{
+	if (freeptr_outside_object(s))
+		return s->inuse + sizeof(void *);
+	else
+		return s->inuse;
+}
+
 /* Loop over all objects in a slab */
 #define for_each_object(__p, __s, __addr, __objects) \
 	for (__p = fixup_red_left(__s, __addr); \
@@ -845,26 +865,6 @@ static void print_section(char *level, char *text, u8 *addr,
 	metadata_access_disable();
 }
 
-/*
- * See comment in calculate_sizes().
- */
-static inline bool freeptr_outside_object(struct kmem_cache *s)
-{
-	return s->offset >= s->inuse;
-}
-
-/*
- * Return offset of the end of info block which is inuse + free pointer if
- * not overlapping with object.
- */
-static inline unsigned int get_info_end(struct kmem_cache *s)
-{
-	if (freeptr_outside_object(s))
-		return s->inuse + sizeof(void *);
-	else
-		return s->inuse;
-}
-
 static struct track *get_track(struct kmem_cache *s, void *object,
 	enum track_item alloc)
 {
@@ -2092,15 +2092,20 @@ bool slab_free_hook(struct kmem_cache *s, void *x, bool init)
 	 *
 	 * The initialization memset's clear the object and the metadata,
 	 * but don't touch the SLAB redzone.
+	 *
+	 * The object's freepointer is also avoided if stored outside the
+	 * object.
 	 */
 	if (unlikely(init)) {
 		int rsize;
+		unsigned int inuse;
 
+		inuse = get_info_end(s);
 		if (!kasan_has_integrated_init())
 			memset(kasan_reset_tag(x), 0, s->object_size);
 		rsize = (s->flags & SLAB_RED_ZONE) ? s->red_left_pad : 0;
-		memset((char *)kasan_reset_tag(x) + s->inuse, 0,
-		       s->size - s->inuse - rsize);
+		memset((char *)kasan_reset_tag(x) + inuse, 0,
+		       s->size - inuse - rsize);
 	}
 	/* KASAN might put x into memory quarantine, delaying its reuse. */
 	return !kasan_slab_free(s, x, init);
@@ -3722,7 +3727,8 @@ static void *__slab_alloc_node(struct kmem_cache *s,
 static __always_inline void maybe_wipe_obj_freeptr(struct kmem_cache *s,
 						   void *obj)
 {
-	if (unlikely(slab_want_init_on_free(s)) && obj)
+	if (unlikely(slab_want_init_on_free(s)) && obj &&
+	    !freeptr_outside_object(s))
 		memset((void *)((char *)kasan_reset_tag(obj) + s->offset),
 			0, sizeof(void *));
 }