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netfilter: nf_tables: fix set->nelems counting with no NLM_F_EXCL 

If the element exists and no NLM_F_EXCL is specified, do not bump
set->nelems, otherwise we leak one set element slot. This problem
amplifies if the set is full since the abort path always decrements the
counter for the -ENFILE case too, giving one spare extra slot.

Fix this by moving set->nelems update to nft_add_set_elem() after
successful element insertion. Moreover, remove the element if the set is
full so there is no need to rely on the abort path to undo things
anymore.

Fixes: c016c7e45d ("netfilter: nf_tables: honor NLM_F_EXCL flag in set element insertion")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Pablo Neira Ayuso 2017-01-24 00:51:32 +01:00
parent 5ce6b04ce9
commit 35d0ac9070
1 changed files with 9 additions and 7 deletions
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16
net/netfilter/nf_tables_api.c
View File

@ -3745,10 +3745,18 @@ static int nft_add_set_elem(struct nft_ctx *ctx, struct nft_set *set,
goto err5;
}
if (set->size &&
!atomic_add_unless(&set->nelems, 1, set->size + set->ndeact)) {
err = -ENFILE;
goto err6;
}
nft_trans_elem(trans) = elem;
list_add_tail(&trans->list, &ctx->net->nft.commit_list);
return 0;
err6:
set->ops->remove(set, &elem);
err5:
kfree(trans);
err4:
@ -3795,15 +3803,9 @@ static int nf_tables_newsetelem(struct net *net, struct sock *nlsk,
return -EBUSY;
nla_for_each_nested(attr, nla[NFTA_SET_ELEM_LIST_ELEMENTS], rem) {
if (set->size &&
!atomic_add_unless(&set->nelems, 1, set->size + set->ndeact))
return -ENFILE;
err = nft_add_set_elem(&ctx, set, attr, nlh->nlmsg_flags);
if (err < 0) {
atomic_dec(&set->nelems);
if (err < 0)
break;
}
}
return err;
}