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netfilter: synproxy: Fix out of bounds when parsing TCP options

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[ Upstream commit 5fc177ab759418c9537433e63301096e733fb915 ]

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 9609dad263 ("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 <92siuyang@gmail.com>
Fixes: 48b1de4c11 ("netfilter: add SYNPROXY core/target")
Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Maxim Mikityanskiy 2021-06-10 19:40:29 +03:00 committed by Greg Kroah-Hartman
parent a336dc6fdd
commit 9cdf299ba4
1 changed files with 5 additions and 0 deletions
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5
net/netfilter/nf_synproxy_core.c
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@ -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,
length--;
continue;
default:
if (length < 2)
return true;
opsize = *ptr++;
if (opsize < 2)
return true;