[PATCH 4.9 098/108] netfilter: nft_log: restrict the log prefix length to 127

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Liping Zhang <zlpnobody@xxxxxxxxx>


[ Upstream commit 5ce6b04ce96896e8a79e6f60740ced911eaac7a4 ]

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: 96518518cc41 ("netfilter: add nftables")
Signed-off-by: Liping Zhang <zlpnobody@xxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 include/uapi/linux/netfilter/nf_log.h |    2 ++
 net/netfilter/nf_log.c                |    1 -
 net/netfilter/nft_log.c               |    3 ++-
 3 files changed, 4 insertions(+), 2 deletions(-)

--- a/include/uapi/linux/netfilter/nf_log.h
+++ b/include/uapi/linux/netfilter/nf_log.h
@@ -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 */
--- a/net/netfilter/nf_log.c
+++ b/net/netfilter/nf_log.c
@@ -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;
--- a/net/netfilter/nft_log.c
+++ b/net/netfilter/nft_log.c
@@ -38,7 +38,8 @@ static void nft_log_eval(const struct nf
 
 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 },