commit 5f3a47f5bb24f5b24ef2a9dc9954ed5221c8abcb Author: Arkadiusz MiĆkiewicz <ar...@maven.pl> Date: Thu Aug 11 00:14:22 2016 +0200
- untested CVE-2016-5696 fix kernel-small_fixes.patch | 81 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 81 insertions(+) --- diff --git a/kernel-small_fixes.patch b/kernel-small_fixes.patch index 0a5d601..f785fa9 100644 --- a/kernel-small_fixes.patch +++ b/kernel-small_fixes.patch @@ -114,3 +114,84 @@ index 29531ec..65fbfb7 100644 goto out_destroy_log; +From 75ff39ccc1bd5d3c455b6822ab09e533c551f758 Mon Sep 17 00:00:00 2001 +From: Eric Dumazet <eduma...@google.com> +Date: Sun, 10 Jul 2016 10:04:02 +0200 +Subject: tcp: make challenge acks less predictable + +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 <ycao...@ucr.edu> +Signed-off-by: Eric Dumazet <eduma...@google.com> +Suggested-by: Linus Torvalds <torva...@linux-foundation.org> +Cc: Yuchung Cheng <ych...@google.com> +Cc: Neal Cardwell <ncardw...@google.com> +Acked-by: Neal Cardwell <ncardw...@google.com> +Acked-by: Yuchung Cheng <ych...@google.com> +Signed-off-by: David S. Miller <da...@davemloft.net> +--- + net/ipv4/tcp_input.c | 15 ++++++++++----- + 1 file changed, 10 insertions(+), 5 deletions(-) + +diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c +index d6c8f4cd0..91868bb 100644 +--- a/net/ipv4/tcp_input.c ++++ b/net/ipv4/tcp_input.c +@@ -87,7 +87,7 @@ 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; +@@ -3458,7 +3458,7 @@ static void tcp_send_challenge_ack(struct sock *sk, const struct sk_buff *skb) + static u32 challenge_timestamp; + static unsigned int challenge_count; + struct tcp_sock *tp = tcp_sk(sk); +- u32 now; ++ u32 count, now; + + /* First check our per-socket dupack rate limit. */ + if (tcp_oow_rate_limited(sock_net(sk), skb, +@@ -3466,13 +3466,18 @@ static void tcp_send_challenge_ack(struct sock *sk, const struct sk_buff *skb) + &tp->last_oow_ack_time)) + return; + +- /* Then check the check host-wide RFC 5961 rate limit. */ ++ /* Then check host-wide RFC 5961 rate limit. */ + now = jiffies / HZ; + 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); + } +-- +cgit v1.0-17-g0c1e3 + ================================================================ ---- gitweb: http://git.pld-linux.org/gitweb.cgi/packages/kernel.git/commitdiff/5f3a47f5bb24f5b24ef2a9dc9954ed5221c8abcb _______________________________________________ pld-cvs-commit mailing list pld-cvs-commit@lists.pld-linux.org http://lists.pld-linux.org/mailman/listinfo/pld-cvs-commit