diff options
authorMaxim Mikityanskiy <>2021-06-10 19:40:29 +0300
committerDavid S. Miller <>2021-06-10 14:26:18 -0700
commit5fc177ab759418c9537433e63301096e733fb915 (patch)
parentd1b5bee4c8be01585033be9b3a8878789285285f (diff)
netfilter: synproxy: Fix out of bounds when parsing TCP options
The TCP option parser in synproxy (synproxy_parse_options) could read one byte out of bounds. When the length is 1, the execution flow gets into the loop, reads one byte of the opcode, and if the opcode is neither TCPOPT_EOL nor TCPOPT_NOP, it reads one more byte, which exceeds the length of 1. This fix is inspired by commit 9609dad263f8 ("ipv4: tcp_input: fix stack out of bounds when parsing TCP options."). v2 changes: Added an early return when length < 0 to avoid calling skb_header_pointer with negative length. Cc: Young Xiao <> Fixes: 48b1de4c110a ("netfilter: add SYNPROXY core/target") Signed-off-by: Maxim Mikityanskiy <> Reviewed-by: Florian Westphal <> Signed-off-by: David S. Miller <>
1 files changed, 5 insertions, 0 deletions
diff --git a/net/netfilter/nf_synproxy_core.c b/net/netfilter/nf_synproxy_core.c
index b100c04a0e43..3d6d49420db8 100644
--- a/net/netfilter/nf_synproxy_core.c
+++ b/net/netfilter/nf_synproxy_core.c
@@ -31,6 +31,9 @@ synproxy_parse_options(const struct sk_buff *skb, unsigned int doff,
int length = (th->doff * 4) - sizeof(*th);
u8 buf[40], *ptr;
+ if (unlikely(length < 0))
+ return false;
ptr = skb_header_pointer(skb, doff + sizeof(*th), length, buf);
if (ptr == NULL)
return false;
@@ -47,6 +50,8 @@ synproxy_parse_options(const struct sk_buff *skb, unsigned int doff,
+ if (length < 2)
+ return true;
opsize = *ptr++;
if (opsize < 2)
return true;