From 8699f49456e1d7e638b11b2397ec72eae5dc2eb9 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sat, 18 May 2019 05:12:05 -0700 Subject: [PATCH] tcp: tcp_fragment() should apply sane memory limits commit f070ef2ac66716357066b683fb0baf55f8191a2e upstream. Jonathan Looney reported that a malicious peer can force a sender to fragment its retransmit queue into tiny skbs, inflating memory usage and/or overflow 32bit counters. TCP allows an application to queue up to sk_sndbuf bytes, so we need to give some allowance for non malicious splitting of retransmit queue. A new SNMP counter is added to monitor how many times TCP did not allow to split an skb if the allowance was exceeded. Note that this counter might increase in the case applications use SO_SNDBUF socket option to lower sk_sndbuf. CVE-2019-11478 : tcp_fragment, prevent fragmenting a packet when the socket is already using more than half the allowed space Signed-off-by: Eric Dumazet Reported-by: Jonathan Looney Acked-by: Neal Cardwell Acked-by: Yuchung Cheng Reviewed-by: Tyler Hicks Cc: Bruce Curtis Cc: Jonathan Lemon Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman Signed-off-by: Jason Xing Signed-off-by: Dust Li --- include/uapi/linux/snmp.h | 1 + net/ipv4/proc.c | 1 + net/ipv4/tcp_output.c | 5 +++++ 3 files changed, 7 insertions(+) diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h index f80135e5feaa..abae27c3001c 100644 --- a/include/uapi/linux/snmp.h +++ b/include/uapi/linux/snmp.h @@ -282,6 +282,7 @@ enum LINUX_MIB_TCPACKCOMPRESSED, /* TCPAckCompressed */ LINUX_MIB_TCPZEROWINDOWDROP, /* TCPZeroWindowDrop */ LINUX_MIB_TCPRCVQDROP, /* TCPRcvQDrop */ + LINUX_MIB_TCPWQUEUETOOBIG, /* TCPWqueueTooBig */ __LINUX_MIB_MAX }; diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c index 70289682a670..eab5c02da8ae 100644 --- a/net/ipv4/proc.c +++ b/net/ipv4/proc.c @@ -290,6 +290,7 @@ static const struct snmp_mib snmp4_net_list[] = { SNMP_MIB_ITEM("TCPAckCompressed", LINUX_MIB_TCPACKCOMPRESSED), SNMP_MIB_ITEM("TCPZeroWindowDrop", LINUX_MIB_TCPZEROWINDOWDROP), SNMP_MIB_ITEM("TCPRcvQDrop", LINUX_MIB_TCPRCVQDROP), + SNMP_MIB_ITEM("TCPWqueueTooBig", LINUX_MIB_TCPWQUEUETOOBIG), SNMP_MIB_SENTINEL }; diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index c8a29601a974..576379f0e6ad 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1299,6 +1299,11 @@ int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue, if (nsize < 0) nsize = 0; + if (unlikely((sk->sk_wmem_queued >> 1) > sk->sk_sndbuf)) { + NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPWQUEUETOOBIG); + return -ENOMEM; + } + if (skb_unclone(skb, gfp)) return -ENOMEM; -- GitLab