netfilter: nfnetlink_log: fix maximum packet length logged to userspace

don't try to queue payloads > 0xffff - NLA_HDRLEN, it does not work.
The nla length includes the size of the nla struct, so anything larger
results in u16 integer overflow.

This patch is similar to
9cefbbc9c8f9abe (netfilter: nfnetlink_queue: cleanup copy_range usage).

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 5 insertions, 3 deletions

diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index 8117fba8e661..2d02eac35415 100644
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -43,7 +43,8 @@
 #define NFULNL_NLBUFSIZ_DEFAULT NLMSG_GOODSIZE
 #define NFULNL_TIMEOUT_DEFAULT  100     /* every second */
 #define NFULNL_QTHRESH_DEFAULT  100     /* 100 packets */
-#define NFULNL_COPY_RANGE_MAX   0xFFFF  /* max packet size is limited by 16-bit struct nfattr nfa_len field */
+/* max packet size is limited by 16-bit struct nfattr nfa_len field */
+#define NFULNL_COPY_RANGE_MAX   (0xFFFF - NLA_HDRLEN)
 
 #define PRINTR(x, args...)      do { if (net_ratelimit()) \
                                      printk(x, ## args); } while (0);
@@ -252,6 +253,8 @@ nfulnl_set_mode(struct nfulnl_instance *inst, u_int8_t mode,
 
         case NFULNL_COPY_PACKET:
                 inst->copy_mode = mode;
+                if (range == 0)
+                        range = NFULNL_COPY_RANGE_MAX;
                 inst->copy_range = min_t(unsigned int,
                                          range, NFULNL_COPY_RANGE_MAX);
                 break;
@@ -679,8 +682,7 @@ nfulnl_log_packet(struct net *net,
                 break;
 
         case NFULNL_COPY_PACKET:
-                if (inst->copy_range == 0
-                    || inst->copy_range > skb->len)
+                if (inst->copy_range > skb->len)
                         data_len = skb->len;
                 else
                         data_len = inst->copy_range;