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netfilter: nft_limit: fix divided by zero panic 

After I input the following nftables rule, a panic happened on my system:
  # nft add rule filter OUTPUT limit rate 0xf00000000 bytes/second

  divide error: 0000 [#1] SMP
  [ ... ]
  RIP: 0010:[<ffffffffa059035e>]  [<ffffffffa059035e>]
  nft_limit_pkt_bytes_eval+0x2e/0xa0 [nft_limit]
  Call Trace:
  [<ffffffffa05721bb>] nft_do_chain+0xfb/0x4e0 [nf_tables]
  [<ffffffffa044f236>] ? nf_nat_setup_info+0x96/0x480 [nf_nat]
  [<ffffffff81753767>] ? ipt_do_table+0x327/0x610
  [<ffffffffa044f677>] ? __nf_nat_alloc_null_binding+0x57/0x80 [nf_nat]
  [<ffffffffa058b21f>] nft_ipv4_output+0xaf/0xd0 [nf_tables_ipv4]
  [<ffffffff816f4aa2>] nf_iterate+0x62/0x80
  [<ffffffff816f4b33>] nf_hook_slow+0x73/0xd0
  [<ffffffff81703d0d>] __ip_local_out+0xcd/0xe0
  [<ffffffff81701d90>] ? ip_forward_options+0x1b0/0x1b0
  [<ffffffff81703d3c>] ip_local_out+0x1c/0x40

This is because divisor is 64-bit, but we treat it as a 32-bit integer,
then 0xf00000000 becomes zero, i.e. divisor becomes 0.

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 2016-09-27 20:49:19 +08:00 committed by Pablo Neira Ayuso
parent dbb5918cb3
commit 2fa46c1301
1 changed files with 2 additions and 2 deletions
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4
net/netfilter/nft_limit.c
View File

@ -145,7 +145,7 @@ static int nft_limit_pkts_init(const struct nft_ctx *ctx,
if (err < 0)
return err;
priv->cost = div_u64(priv->limit.nsecs, priv->limit.rate);
priv->cost = div64_u64(priv->limit.nsecs, priv->limit.rate);
return 0;
}
@ -170,7 +170,7 @@ static void nft_limit_pkt_bytes_eval(const struct nft_expr *expr,
const struct nft_pktinfo *pkt)
{
struct nft_limit *priv = nft_expr_priv(expr);
u64 cost = div_u64(priv->nsecs * pkt->skb->len, priv->rate);
u64 cost = div64_u64(priv->nsecs * pkt->skb->len, priv->rate);
if (nft_limit_eval(priv, cost))
regs->verdict.code = NFT_BREAK;