From bd05c1b998faec5f6d9f64088c1b8f4d53f0dade Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sun, 10 Jul 2016 10:04:02 +0200 Subject: [PATCH 1/2] BACKPORT: tcp: make challenge acks less predictable (cherry picked from commit 75ff39ccc1bd5d3c455b6822ab09e533c551f758) Yue Cao claims that current host rate limiting of challenge ACKS (RFC 5961) could leak enough information to allow a patient attacker to hijack TCP sessions. He will soon provide details in an academic paper. This patch increases the default limit from 100 to 1000, and adds some randomization so that the attacker can no longer hijack sessions without spending a considerable amount of probes. Based on initial analysis and patch from Linus. Note that we also have per socket rate limiting, so it is tempting to remove the host limit in the future. v2: randomize the count of challenge acks per second, not the period. Fixes: 282f23c6ee34 ("tcp: implement RFC 5961 3.2") Reported-by: Yue Cao Signed-off-by: Eric Dumazet Suggested-by: Linus Torvalds Cc: Yuchung Cheng Cc: Neal Cardwell Acked-by: Neal Cardwell Acked-by: Yuchung Cheng Signed-off-by: David S. Miller Change-Id: Ib46ba66f5e4a5a7c81bfccd7b0aa83c3d9e1b3bb Bug: 30809774 --- net/ipv4/tcp_input.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 055b7ddf9fb8..212fe15905e4 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -88,7 +88,7 @@ int sysctl_tcp_adv_win_scale __read_mostly = 1; EXPORT_SYMBOL(sysctl_tcp_adv_win_scale); /* rfc5961 challenge ack rate limiting */ -int sysctl_tcp_challenge_ack_limit = 100; +int sysctl_tcp_challenge_ack_limit = 1000; int sysctl_tcp_stdurg __read_mostly; int sysctl_tcp_rfc1337 __read_mostly; @@ -3326,12 +3326,18 @@ static void tcp_send_challenge_ack(struct sock *sk) static u32 challenge_timestamp; static unsigned int challenge_count; u32 now = jiffies / HZ; + u32 count; if (now != challenge_timestamp) { + u32 half = (sysctl_tcp_challenge_ack_limit + 1) >> 1; + challenge_timestamp = now; - challenge_count = 0; + WRITE_ONCE(challenge_count, half + + prandom_u32_max(sysctl_tcp_challenge_ack_limit)); } - if (++challenge_count <= sysctl_tcp_challenge_ack_limit) { + count = READ_ONCE(challenge_count); + if (count > 0) { + WRITE_ONCE(challenge_count, count - 1); NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPCHALLENGEACK); tcp_send_ack(sk); } From 18acd215d8392fc402933b66358fa15b2ee4b757 Mon Sep 17 00:00:00 2001 From: Mohamad Ayyash Date: Tue, 24 May 2016 15:33:56 -0700 Subject: [PATCH 2/2] Replace %p with %pK to prevent leaking kernel address BUG: 27532522 Change-Id: Ic0710a9a8cfc682acd88ecf3bbfeece2d798c4a4 Signed-off-by: Mohamad Ayyash --- net/netfilter/xt_qtaguid.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/netfilter/xt_qtaguid.c b/net/netfilter/xt_qtaguid.c index 45df66f62f7d..bd27e833e9db 100644 --- a/net/netfilter/xt_qtaguid.c +++ b/net/netfilter/xt_qtaguid.c @@ -1979,7 +1979,7 @@ static int qtaguid_ctrl_proc_show(struct seq_file *m, void *v) ); f_count = atomic_long_read( &sock_tag_entry->socket->file->f_count); - seq_printf(m, "sock=%p tag=0x%llx (uid=%u) pid=%u " + seq_printf(m, "sock=%pK tag=0x%llx (uid=%u) pid=%u " "f_count=%lu\n", sock_tag_entry->sk, sock_tag_entry->tag, uid,