From cfac7f836a715b91f08c851df915d401a4d52783 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 1 Dec 2017 10:06:56 -0800 Subject: tcp/dccp: block bh before arming time_wait timer MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Maciej Żenczykowski reported some panics in tcp_twsk_destructor() that might be caused by the following bug. timewait timer is pinned to the cpu, because we want to transition timwewait refcount from 0 to 4 in one go, once everything has been initialized. At the time commit ed2e92394589 ("tcp/dccp: fix timewait races in timer handling") was merged, TCP was always running from BH habdler. After commit 5413d1babe8f ("net: do not block BH while processing socket backlog") we definitely can run tcp_time_wait() from process context. We need to block BH in the critical section so that the pinned timer has still its purpose. This bug is more likely to happen under stress and when very small RTO are used in datacenter flows. Fixes: 5413d1babe8f ("net: do not block BH while processing socket backlog") Signed-off-by: Eric Dumazet Reported-by: Maciej Żenczykowski Acked-by: Maciej Żenczykowski Signed-off-by: David S. Miller --- net/ipv4/tcp_minisocks.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'net/ipv4') diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index e36eff0403f4..b079b619b60c 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -310,10 +310,16 @@ void tcp_time_wait(struct sock *sk, int state, int timeo) if (state == TCP_TIME_WAIT) timeo = TCP_TIMEWAIT_LEN; + /* tw_timer is pinned, so we need to make sure BH are disabled + * in following section, otherwise timer handler could run before + * we complete the initialization. + */ + local_bh_disable(); inet_twsk_schedule(tw, timeo); /* Linkage updates. */ __inet_twsk_hashdance(tw, sk, &tcp_hashinfo); inet_twsk_put(tw); + local_bh_enable(); } else { /* Sorry, if we're out of memory, just CLOSE this * socket up. We've got bigger problems than -- cgit v1.2.3 From eeea10b83a139451130df1594f26710c8fa390c8 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sun, 3 Dec 2017 09:32:59 -0800 Subject: tcp: add tcp_v4_fill_cb()/tcp_v4_restore_cb() James Morris reported kernel stack corruption bug [1] while running the SELinux testsuite, and bisected to a recent commit bffa72cf7f9d ("net: sk_buff rbnode reorg") We believe this commit is fine, but exposes an older bug. SELinux code runs from tcp_filter() and might send an ICMP, expecting IP options to be found in skb->cb[] using regular IPCB placement. We need to defer TCP mangling of skb->cb[] after tcp_filter() calls. This patch adds tcp_v4_fill_cb()/tcp_v4_restore_cb() in a very similar way we added them for IPv6. [1] [ 339.806024] SELinux: failure in selinux_parse_skb(), unable to parse packet [ 339.822505] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: ffffffff81745af5 [ 339.822505] [ 339.852250] CPU: 4 PID: 3642 Comm: client Not tainted 4.15.0-rc1-test #15 [ 339.868498] Hardware name: LENOVO 10FGS0VA1L/30BC, BIOS FWKT68A 01/19/2017 [ 339.885060] Call Trace: [ 339.896875] [ 339.908103] dump_stack+0x63/0x87 [ 339.920645] panic+0xe8/0x248 [ 339.932668] ? ip_push_pending_frames+0x33/0x40 [ 339.946328] ? icmp_send+0x525/0x530 [ 339.958861] ? kfree_skbmem+0x60/0x70 [ 339.971431] __stack_chk_fail+0x1b/0x20 [ 339.984049] icmp_send+0x525/0x530 [ 339.996205] ? netlbl_skbuff_err+0x36/0x40 [ 340.008997] ? selinux_netlbl_err+0x11/0x20 [ 340.021816] ? selinux_socket_sock_rcv_skb+0x211/0x230 [ 340.035529] ? security_sock_rcv_skb+0x3b/0x50 [ 340.048471] ? sk_filter_trim_cap+0x44/0x1c0 [ 340.061246] ? tcp_v4_inbound_md5_hash+0x69/0x1b0 [ 340.074562] ? tcp_filter+0x2c/0x40 [ 340.086400] ? tcp_v4_rcv+0x820/0xa20 [ 340.098329] ? ip_local_deliver_finish+0x71/0x1a0 [ 340.111279] ? ip_local_deliver+0x6f/0xe0 [ 340.123535] ? ip_rcv_finish+0x3a0/0x3a0 [ 340.135523] ? ip_rcv_finish+0xdb/0x3a0 [ 340.147442] ? ip_rcv+0x27c/0x3c0 [ 340.158668] ? inet_del_offload+0x40/0x40 [ 340.170580] ? __netif_receive_skb_core+0x4ac/0x900 [ 340.183285] ? rcu_accelerate_cbs+0x5b/0x80 [ 340.195282] ? __netif_receive_skb+0x18/0x60 [ 340.207288] ? process_backlog+0x95/0x140 [ 340.218948] ? net_rx_action+0x26c/0x3b0 [ 340.230416] ? __do_softirq+0xc9/0x26a [ 340.241625] ? do_softirq_own_stack+0x2a/0x40 [ 340.253368] [ 340.262673] ? do_softirq+0x50/0x60 [ 340.273450] ? __local_bh_enable_ip+0x57/0x60 [ 340.285045] ? ip_finish_output2+0x175/0x350 [ 340.296403] ? ip_finish_output+0x127/0x1d0 [ 340.307665] ? nf_hook_slow+0x3c/0xb0 [ 340.318230] ? ip_output+0x72/0xe0 [ 340.328524] ? ip_fragment.constprop.54+0x80/0x80 [ 340.340070] ? ip_local_out+0x35/0x40 [ 340.350497] ? ip_queue_xmit+0x15c/0x3f0 [ 340.361060] ? __kmalloc_reserve.isra.40+0x31/0x90 [ 340.372484] ? __skb_clone+0x2e/0x130 [ 340.382633] ? tcp_transmit_skb+0x558/0xa10 [ 340.393262] ? tcp_connect+0x938/0xad0 [ 340.403370] ? ktime_get_with_offset+0x4c/0xb0 [ 340.414206] ? tcp_v4_connect+0x457/0x4e0 [ 340.424471] ? __inet_stream_connect+0xb3/0x300 [ 340.435195] ? inet_stream_connect+0x3b/0x60 [ 340.445607] ? SYSC_connect+0xd9/0x110 [ 340.455455] ? __audit_syscall_entry+0xaf/0x100 [ 340.466112] ? syscall_trace_enter+0x1d0/0x2b0 [ 340.476636] ? __audit_syscall_exit+0x209/0x290 [ 340.487151] ? SyS_connect+0xe/0x10 [ 340.496453] ? do_syscall_64+0x67/0x1b0 [ 340.506078] ? entry_SYSCALL64_slow_path+0x25/0x25 Fixes: 971f10eca186 ("tcp: better TCP_SKB_CB layout to reduce cache line misses") Signed-off-by: Eric Dumazet Reported-by: James Morris Tested-by: James Morris Tested-by: Casey Schaufler Signed-off-by: David S. Miller --- net/ipv4/tcp_ipv4.c | 59 ++++++++++++++++++++++++++++++++++++----------------- 1 file changed, 40 insertions(+), 19 deletions(-) (limited to 'net/ipv4') diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index c6bc0c4d19c6..77ea45da0fe9 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1591,6 +1591,34 @@ int tcp_filter(struct sock *sk, struct sk_buff *skb) } EXPORT_SYMBOL(tcp_filter); +static void tcp_v4_restore_cb(struct sk_buff *skb) +{ + memmove(IPCB(skb), &TCP_SKB_CB(skb)->header.h4, + sizeof(struct inet_skb_parm)); +} + +static void tcp_v4_fill_cb(struct sk_buff *skb, const struct iphdr *iph, + const struct tcphdr *th) +{ + /* This is tricky : We move IPCB at its correct location into TCP_SKB_CB() + * barrier() makes sure compiler wont play fool^Waliasing games. + */ + memmove(&TCP_SKB_CB(skb)->header.h4, IPCB(skb), + sizeof(struct inet_skb_parm)); + barrier(); + + TCP_SKB_CB(skb)->seq = ntohl(th->seq); + TCP_SKB_CB(skb)->end_seq = (TCP_SKB_CB(skb)->seq + th->syn + th->fin + + skb->len - th->doff * 4); + TCP_SKB_CB(skb)->ack_seq = ntohl(th->ack_seq); + TCP_SKB_CB(skb)->tcp_flags = tcp_flag_byte(th); + TCP_SKB_CB(skb)->tcp_tw_isn = 0; + TCP_SKB_CB(skb)->ip_dsfield = ipv4_get_dsfield(iph); + TCP_SKB_CB(skb)->sacked = 0; + TCP_SKB_CB(skb)->has_rxtstamp = + skb->tstamp || skb_hwtstamps(skb)->hwtstamp; +} + /* * From tcp_input.c */ @@ -1631,24 +1659,6 @@ int tcp_v4_rcv(struct sk_buff *skb) th = (const struct tcphdr *)skb->data; iph = ip_hdr(skb); - /* This is tricky : We move IPCB at its correct location into TCP_SKB_CB() - * barrier() makes sure compiler wont play fool^Waliasing games. - */ - memmove(&TCP_SKB_CB(skb)->header.h4, IPCB(skb), - sizeof(struct inet_skb_parm)); - barrier(); - - TCP_SKB_CB(skb)->seq = ntohl(th->seq); - TCP_SKB_CB(skb)->end_seq = (TCP_SKB_CB(skb)->seq + th->syn + th->fin + - skb->len - th->doff * 4); - TCP_SKB_CB(skb)->ack_seq = ntohl(th->ack_seq); - TCP_SKB_CB(skb)->tcp_flags = tcp_flag_byte(th); - TCP_SKB_CB(skb)->tcp_tw_isn = 0; - TCP_SKB_CB(skb)->ip_dsfield = ipv4_get_dsfield(iph); - TCP_SKB_CB(skb)->sacked = 0; - TCP_SKB_CB(skb)->has_rxtstamp = - skb->tstamp || skb_hwtstamps(skb)->hwtstamp; - lookup: sk = __inet_lookup_skb(&tcp_hashinfo, skb, __tcp_hdrlen(th), th->source, th->dest, sdif, &refcounted); @@ -1679,14 +1689,19 @@ process: sock_hold(sk); refcounted = true; nsk = NULL; - if (!tcp_filter(sk, skb)) + if (!tcp_filter(sk, skb)) { + th = (const struct tcphdr *)skb->data; + iph = ip_hdr(skb); + tcp_v4_fill_cb(skb, iph, th); nsk = tcp_check_req(sk, skb, req, false); + } if (!nsk) { reqsk_put(req); goto discard_and_relse; } if (nsk == sk) { reqsk_put(req); + tcp_v4_restore_cb(skb); } else if (tcp_child_process(sk, nsk, skb)) { tcp_v4_send_reset(nsk, skb); goto discard_and_relse; @@ -1712,6 +1727,7 @@ process: goto discard_and_relse; th = (const struct tcphdr *)skb->data; iph = ip_hdr(skb); + tcp_v4_fill_cb(skb, iph, th); skb->dev = NULL; @@ -1742,6 +1758,8 @@ no_tcp_socket: if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) goto discard_it; + tcp_v4_fill_cb(skb, iph, th); + if (tcp_checksum_complete(skb)) { csum_error: __TCP_INC_STATS(net, TCP_MIB_CSUMERRORS); @@ -1768,6 +1786,8 @@ do_time_wait: goto discard_it; } + tcp_v4_fill_cb(skb, iph, th); + if (tcp_checksum_complete(skb)) { inet_twsk_put(inet_twsk(sk)); goto csum_error; @@ -1784,6 +1804,7 @@ do_time_wait: if (sk2) { inet_twsk_deschedule_put(inet_twsk(sk)); sk = sk2; + tcp_v4_restore_cb(skb); refcounted = false; goto process; } -- cgit v1.2.3