netfilter: nft_log: restrict the log prefix length to 127 (5ce6b04c) · Commits · 戴 / test

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: ("netfilter: add nftables") Signed-off-by:

Liping Zhang <zlpnobody@gmail.com> Signed-off-by:

Pablo Neira Ayuso <pablo@netfilter.org>

include/uapi/linux/netfilter/nf_log.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -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 */

net/netfilter/nf_log.c

+0 −1

Original line number	Diff line number	Diff line
		@@ -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;

net/netfilter/nft_log.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -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 },

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