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Date: Sun, 3 Dec 2017 09:32:59 -0800
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>,
Eric Dumazet <eric.dumazet@...il.com>,
David Ahern <dsa@...ulusnetworks.com>,
James Morris <james.l.morris@...cle.com>,
Casey Schaufler <casey@...aufler-ca.com>,
Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net 1/2] 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] <IRQ>
[ 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] </IRQ>
[ 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 <edumazet@...gle.com>
Reported-by: James Morris <james.l.morris@...cle.com>
Tested-by: James Morris <james.l.morris@...cle.com>
Tested-by: Casey Schaufler <casey@...aufler-ca.com>
---
net/ipv4/tcp_ipv4.c | 59 ++++++++++++++++++++++++++++++++++++-----------------
net/ipv6/tcp_ipv6.c | 10 +++++----
2 files changed, 46 insertions(+), 23 deletions(-)
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index c6bc0c4d19c624888b0d0b5a4246c7183edf63f5..77ea45da0fe9c746907a312989658af3ad3b198d 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 @@ int tcp_v4_rcv(struct sk_buff *skb)
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 @@ int tcp_v4_rcv(struct sk_buff *skb)
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 @@ int tcp_v4_rcv(struct sk_buff *skb)
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 @@ int tcp_v4_rcv(struct sk_buff *skb)
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 @@ int tcp_v4_rcv(struct sk_buff *skb)
if (sk2) {
inet_twsk_deschedule_put(inet_twsk(sk));
sk = sk2;
+ tcp_v4_restore_cb(skb);
refcounted = false;
goto process;
}
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index be11dc13aa705145a83177e17d23594e9416e11a..1f04ec0e4a7aa2c11b8ee27cbdd4067b5bcf32e5 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1454,7 +1454,6 @@ static int tcp_v6_rcv(struct sk_buff *skb)
struct sock *nsk;
sk = req->rsk_listener;
- tcp_v6_fill_cb(skb, hdr, th);
if (tcp_v6_inbound_md5_hash(sk, skb)) {
sk_drops_add(sk, skb);
reqsk_put(req);
@@ -1467,8 +1466,12 @@ static int tcp_v6_rcv(struct sk_buff *skb)
sock_hold(sk);
refcounted = true;
nsk = NULL;
- if (!tcp_filter(sk, skb))
+ if (!tcp_filter(sk, skb)) {
+ th = (const struct tcphdr *)skb->data;
+ hdr = ipv6_hdr(skb);
+ tcp_v6_fill_cb(skb, hdr, th);
nsk = tcp_check_req(sk, skb, req, false);
+ }
if (!nsk) {
reqsk_put(req);
goto discard_and_relse;
@@ -1492,8 +1495,6 @@ static int tcp_v6_rcv(struct sk_buff *skb)
if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
goto discard_and_relse;
- tcp_v6_fill_cb(skb, hdr, th);
-
if (tcp_v6_inbound_md5_hash(sk, skb))
goto discard_and_relse;
@@ -1501,6 +1502,7 @@ static int tcp_v6_rcv(struct sk_buff *skb)
goto discard_and_relse;
th = (const struct tcphdr *)skb->data;
hdr = ipv6_hdr(skb);
+ tcp_v6_fill_cb(skb, hdr, th);
skb->dev = NULL;
--
2.15.0.531.g2ccb3012c9-goog
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