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netfilter: nft_numgen: fix race between num generate and store it

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After we generate a new number, we still use the priv->counter and
store it to the dreg. This is not correct, another cpu may already
change it to a new number. So we must use the generated number, not
the priv->counter itself.

Fixes: 91dbc6be0a ("netfilter: nf_tables: add number generator expression")
Signed-off-by: Liping Zhang <liping.zhang@spreadtrum.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Liping Zhang 2016-09-12 22:21:36 +08:00 committed by Pablo Neira Ayuso
parent 8e8118f893
commit 2e917d602a
1 changed files with 1 additions and 1 deletions
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2
net/netfilter/nft_numgen.c
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@ -37,7 +37,7 @@ static void nft_ng_inc_eval(const struct nft_expr *expr,
nval = (oval + 1 < priv->modulus) ? oval + 1 : 0;
} while (atomic_cmpxchg(&priv->counter, oval, nval) != oval);
memcpy(&regs->data[priv->dreg], &priv->counter, sizeof(u32));
regs->data[priv->dreg] = nval;
}
static const struct nla_policy nft_ng_policy[NFTA_NG_MAX + 1] = {