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net: convert sk_buff_fclones.fclone_ref from atomic_t to refcount_t

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refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Reshetova, Elena 2017-06-30 13:07:59 +03:00 committed by David S. Miller
parent 633547973f
commit 2638595afc
2 changed files with 7 additions and 7 deletions
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4
include/linux/skbuff.h
View File

@ -915,7 +915,7 @@ struct sk_buff_fclones {
struct sk_buff skb2;
atomic_t fclone_ref;
refcount_t fclone_ref;
};
/**
@ -935,7 +935,7 @@ static inline bool skb_fclone_busy(const struct sock *sk,
fclones = container_of(skb, struct sk_buff_fclones, skb1);
return skb->fclone == SKB_FCLONE_ORIG &&
atomic_read(&fclones->fclone_ref) > 1 &&
refcount_read(&fclones->fclone_ref) > 1 &&
fclones->skb2.sk == sk;
}

10
net/core/skbuff.c
View File

@ -268,7 +268,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
kmemcheck_annotate_bitfield(&fclones->skb2, flags1);
skb->fclone = SKB_FCLONE_ORIG;
atomic_set(&fclones->fclone_ref, 1);
refcount_set(&fclones->fclone_ref, 1);
fclones->skb2.fclone = SKB_FCLONE_CLONE;
}
@ -629,7 +629,7 @@ static void kfree_skbmem(struct sk_buff *skb)
* This test would have no chance to be true for the clone,
* while here, branch prediction will be good.
*/
if (atomic_read(&fclones->fclone_ref) == 1)
if (refcount_read(&fclones->fclone_ref) == 1)
goto fastpath;
break;
@ -637,7 +637,7 @@ static void kfree_skbmem(struct sk_buff *skb)
fclones = container_of(skb, struct sk_buff_fclones, skb2);
break;
}
if (!atomic_dec_and_test(&fclones->fclone_ref))
if (!refcount_dec_and_test(&fclones->fclone_ref))
return;
fastpath:
kmem_cache_free(skbuff_fclone_cache, fclones);
@ -1027,9 +1027,9 @@ struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
return NULL;
if (skb->fclone == SKB_FCLONE_ORIG &&
atomic_read(&fclones->fclone_ref) == 1) {
refcount_read(&fclones->fclone_ref) == 1) {
n = &fclones->skb2;
atomic_set(&fclones->fclone_ref, 2);
refcount_set(&fclones->fclone_ref, 2);
} else {
if (skb_pfmemalloc(skb))
gfp_mask |= __GFP_MEMALLOC;