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slab fixes for 6.9-rc7

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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
This commit is contained in:
Linus Torvalds 2024-05-06 10:27:58 -07:00
commit ee5b455b0a
2 changed files with 31 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/slab.h
View File

@ -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);

52
mm/slub.c
View File

@ -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 *));
}