diff options
author | Eric Dumazet <edumazet@google.com> | 2019-12-05 10:10:15 -0800 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-12-21 10:47:35 +0100 |
commit | 3485dc1441b8037945a29217ab745f456f96450e (patch) | |
tree | 22703f85ab9fac1e205f967313fe2d1197d7b1d9 /net | |
parent | 22f73f807e3dce32313ae7c87d81c95d4d8e7b66 (diff) |
tcp: md5: fix potential overestimation of TCP option space
[ Upstream commit 9424e2e7ad93ffffa88f882c9bc5023570904b55 ]
Back in 2008, Adam Langley fixed the corner case of packets for flows
having all of the following options : MD5 TS SACK
Since MD5 needs 20 bytes, and TS needs 12 bytes, no sack block
can be cooked from the remaining 8 bytes.
tcp_established_options() correctly sets opts->num_sack_blocks
to zero, but returns 36 instead of 32.
This means TCP cooks packets with 4 extra bytes at the end
of options, containing unitialized bytes.
Fixes: 33ad798c924b ("tcp: options clean up")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net')
-rw-r--r-- | net/ipv4/tcp_output.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 6025cc509d97..e3b28140c10b 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -708,8 +708,9 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb min_t(unsigned int, eff_sacks, (remaining - TCPOLEN_SACK_BASE_ALIGNED) / TCPOLEN_SACK_PERBLOCK); - size += TCPOLEN_SACK_BASE_ALIGNED + - opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK; + if (likely(opts->num_sack_blocks)) + size += TCPOLEN_SACK_BASE_ALIGNED + + opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK; } return size; |