freelist_dereference() is a one-liner only used from get_freepointer().
Remove it and make get_freepointer() call freelist_ptr_decode()
directly to make the code easier to follow.
Signed-off-by: Vlastimil Babka <[email protected]>
---
mm/slub.c | 16 ++++++----------
1 file changed, 6 insertions(+), 10 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index 07edad305512..c4556a5dab4b 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -397,18 +397,14 @@ static inline void *freelist_ptr_decode(const struct kmem_cache *s,
return decoded;
}
-/* Returns the freelist pointer recorded at location ptr_addr. */
-static inline void *freelist_dereference(const struct kmem_cache *s,
- void *ptr_addr)
-{
- return freelist_ptr_decode(s, *(freeptr_t *)(ptr_addr),
- (unsigned long)ptr_addr);
-}
-
static inline void *get_freepointer(struct kmem_cache *s, void *object)
{
- object = kasan_reset_tag(object);
- return freelist_dereference(s, (freeptr_t *)(object + s->offset));
+ unsigned long ptr_addr;
+ freeptr_t p;
+
+ ptr_addr = ((unsigned long)kasan_reset_tag(object)) + s->offset;
+ p = *(freeptr_t *)(ptr_addr);
+ return freelist_ptr_decode(s, p, ptr_addr);
}
#ifndef CONFIG_SLUB_TINY
--
2.41.0
On Tue, Jul 11, 2023 at 03:46:25PM +0200, Vlastimil Babka wrote:
> freelist_dereference() is a one-liner only used from get_freepointer().
> Remove it and make get_freepointer() call freelist_ptr_decode()
> directly to make the code easier to follow.
>
> Signed-off-by: Vlastimil Babka <[email protected]>
> ---
> mm/slub.c | 16 ++++++----------
> 1 file changed, 6 insertions(+), 10 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index 07edad305512..c4556a5dab4b 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -397,18 +397,14 @@ static inline void *freelist_ptr_decode(const struct kmem_cache *s,
> return decoded;
> }
>
> -/* Returns the freelist pointer recorded at location ptr_addr. */
> -static inline void *freelist_dereference(const struct kmem_cache *s,
> - void *ptr_addr)
> -{
> - return freelist_ptr_decode(s, *(freeptr_t *)(ptr_addr),
> - (unsigned long)ptr_addr);
> -}
> -
> static inline void *get_freepointer(struct kmem_cache *s, void *object)
> {
> - object = kasan_reset_tag(object);
> - return freelist_dereference(s, (freeptr_t *)(object + s->offset));
> + unsigned long ptr_addr;
> + freeptr_t p;
> +
> + ptr_addr = ((unsigned long)kasan_reset_tag(object)) + s->offset;
> + p = *(freeptr_t *)(ptr_addr);
> + return freelist_ptr_decode(s, p, ptr_addr);
> }
>
> #ifndef CONFIG_SLUB_TINY
> --
> 2.41.0
>
I like reducing the complexity here, but I find dropping the "object"
reassignment makes this a bit harder to read. What about:
object = kasan_reset_tag(object);
unsigned long ptr_addr = (unsigned long)object + s->offset;
freeptr_t p = *(freeptr_t *)(ptr_addr);
return freelist_ptr_decode(s, p, ptr_addr);
?
They're the same result, so either way:
Acked-by: Kees Cook <[email protected]>
--
Kees Cook
On 7/11/23 18:21, Kees Cook wrote:
> On Tue, Jul 11, 2023 at 03:46:25PM +0200, Vlastimil Babka wrote:
>>
>> #ifndef CONFIG_SLUB_TINY
>> --
>> 2.41.0
>>
>
> I like reducing the complexity here, but I find dropping the "object"
> reassignment makes this a bit harder to read. What about:
Alright.
> object = kasan_reset_tag(object);
> unsigned long ptr_addr = (unsigned long)object + s->offset;
> freeptr_t p = *(freeptr_t *)(ptr_addr);
Are we really so benevolent with declaration-after-statement now? :)
> return freelist_ptr_decode(s, p, ptr_addr);
>
> ?
>
> They're the same result, so either way:
>
> Acked-by: Kees Cook <[email protected]>
>
On 7/13/23 09:44, Vlastimil Babka wrote:
> On 7/11/23 18:21, Kees Cook wrote:
>> On Tue, Jul 11, 2023 at 03:46:25PM +0200, Vlastimil Babka wrote:
>>>
>>> #ifndef CONFIG_SLUB_TINY
>>> --
>>> 2.41.0
>>>
>>
>> I like reducing the complexity here, but I find dropping the "object"
>> reassignment makes this a bit harder to read. What about:
>
> Alright.
>
>> object = kasan_reset_tag(object);
>> unsigned long ptr_addr = (unsigned long)object + s->offset;
>> freeptr_t p = *(freeptr_t *)(ptr_addr);
>
> Are we really so benevolent with declaration-after-statement now? :)
I've left the declarations separate for now so it's similar to
get_freepointer_safe(). Pushed the result to slab/for-6.6/cleanup and
for-next. Thanks for the reviews!
>> return freelist_ptr_decode(s, p, ptr_addr);
>>
>> ?
>>
>> They're the same result, so either way:
>>
>> Acked-by: Kees Cook <[email protected]>
>>
>