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SubjectRe: [PATCH 2/5] kasan, kmemleak: pass tagged pointers to kmemleak
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On 11/02/2019 21:59, Andrey Konovalov wrote:
> Right now we call kmemleak hooks before assigning tags to pointers in
> KASAN hooks. As a result, when an objects gets allocated, kmemleak sees
> a differently tagged pointer, compared to the one it sees when the object
> gets freed. Fix it by calling KASAN hooks before kmemleak's ones.
>

Nit: Could you please add comments to the the code? It should prevent that the
code gets refactored in future, reintroducing the same issue.

> Reported-by: Qian Cai <cai@lca.pw>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> ---
> mm/slab.h | 6 ++----
> mm/slab_common.c | 2 +-
> mm/slub.c | 3 ++-
> 3 files changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/mm/slab.h b/mm/slab.h
> index 4190c24ef0e9..638ea1b25d39 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -437,11 +437,9 @@ static inline void slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags,
>
> flags &= gfp_allowed_mask;
> for (i = 0; i < size; i++) {
> - void *object = p[i];
> -
> - kmemleak_alloc_recursive(object, s->object_size, 1,
> + p[i] = kasan_slab_alloc(s, p[i], flags);
> + kmemleak_alloc_recursive(p[i], s->object_size, 1,
> s->flags, flags);
> - p[i] = kasan_slab_alloc(s, object, flags);
> }
>
> if (memcg_kmem_enabled())
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 81732d05e74a..fe524c8d0246 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -1228,8 +1228,8 @@ void *kmalloc_order(size_t size, gfp_t flags, unsigned int order)
> flags |= __GFP_COMP;
> page = alloc_pages(flags, order);
> ret = page ? page_address(page) : NULL;
> - kmemleak_alloc(ret, size, 1, flags);
> ret = kasan_kmalloc_large(ret, size, flags);
> + kmemleak_alloc(ret, size, 1, flags);
> return ret;
> }
> EXPORT_SYMBOL(kmalloc_order);
> diff --git a/mm/slub.c b/mm/slub.c
> index 1e3d0ec4e200..4a3d7686902f 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -1374,8 +1374,9 @@ static inline void dec_slabs_node(struct kmem_cache *s, int node,
> */
> static inline void *kmalloc_large_node_hook(void *ptr, size_t size, gfp_t flags)
> {
> + ptr = kasan_kmalloc_large(ptr, size, flags);
> kmemleak_alloc(ptr, size, 1, flags);
> - return kasan_kmalloc_large(ptr, size, flags);
> + return ptr;
> }
>
> static __always_inline void kfree_hook(void *x)
>

--
Regards,
Vincenzo

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