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netfilter: nft_log: restrict the log prefix length to 127

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First, log prefix will be truncated to NF_LOG_PREFIXLEN-1, i.e. 127,
at nf_log_packet(), so the extra part is useless.

Second, after adding a log rule with a very very long prefix, we will
fail to dump the nft rules after this _special_ one, but acctually,
they do exist. For example:
  # name_65000=$(printf "%0.sQ" {1..65000})
  # nft add rule filter output log prefix "$name_65000"
  # nft add rule filter output counter
  # nft add rule filter output counter
  # nft list chain filter output
  table ip filter {
      chain output {
          type filter hook output priority 0; policy accept;
      }
  }

So now, restrict the log prefix length to NF_LOG_PREFIXLEN-1.

Fixes: 96518518cc ("netfilter: add nftables")
Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Liping Zhang 2017-01-22 22:10:32 +08:00 committed by Pablo Neira Ayuso
parent b2fbd04498
commit 5ce6b04ce9
3 changed files with 4 additions and 2 deletions
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2
include/uapi/linux/netfilter/nf_log.h
View File

@ -9,4 +9,6 @@
#define NF_LOG_MACDECODE 0x20 /* Decode MAC header */
#define NF_LOG_MASK 0x2f
#define NF_LOG_PREFIXLEN 128
#endif /* _NETFILTER_NF_LOG_H */

1
net/netfilter/nf_log.c
View File

@ -13,7 +13,6 @@
/* Internal logging interface, which relies on the real
LOG target modules */
#define NF_LOG_PREFIXLEN 128
#define NFLOGGER_NAME_LEN 64
static struct nf_logger __rcu *loggers[NFPROTO_NUMPROTO][NF_LOG_TYPE_MAX] __read_mostly;

3
net/netfilter/nft_log.c
View File

@ -39,7 +39,8 @@ static void nft_log_eval(const struct nft_expr *expr,
static const struct nla_policy nft_log_policy[NFTA_LOG_MAX + 1] = {
[NFTA_LOG_GROUP] = { .type = NLA_U16 },
[NFTA_LOG_PREFIX] = { .type = NLA_STRING },
[NFTA_LOG_PREFIX] = { .type = NLA_STRING,
.len = NF_LOG_PREFIXLEN - 1 },
[NFTA_LOG_SNAPLEN] = { .type = NLA_U32 },
[NFTA_LOG_QTHRESHOLD] = { .type = NLA_U16 },
[NFTA_LOG_LEVEL] = { .type = NLA_U32 },