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Subject[PATCH 3.18 17/29] net: dccp: avoid crash in ccid3_hc_rx_send_feedback()
Date
3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 74174fe5634ffbf645a7ca5a261571f700b2f332 ]

On fast hosts or malicious bots, we trigger a DCCP_BUG() which
seems excessive.

syzbot reported :

BUG: delta (-6195) <= 0 at net/dccp/ccids/ccid3.c:628/ccid3_hc_rx_send_feedback()
CPU: 1 PID: 18 Comm: ksoftirqd/1 Not tainted 4.18.0-rc1+ #112
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
ccid3_hc_rx_send_feedback net/dccp/ccids/ccid3.c:628 [inline]
ccid3_hc_rx_packet_recv.cold.16+0x38/0x71 net/dccp/ccids/ccid3.c:793
ccid_hc_rx_packet_recv net/dccp/ccid.h:185 [inline]
dccp_deliver_input_to_ccids+0xf0/0x280 net/dccp/input.c:180
dccp_rcv_established+0x87/0xb0 net/dccp/input.c:378
dccp_v4_do_rcv+0x153/0x180 net/dccp/ipv4.c:654
sk_backlog_rcv include/net/sock.h:914 [inline]
__sk_receive_skb+0x3ba/0xd80 net/core/sock.c:517
dccp_v4_rcv+0x10f9/0x1f58 net/dccp/ipv4.c:875
ip_local_deliver_finish+0x2eb/0xda0 net/ipv4/ip_input.c:215
NF_HOOK include/linux/netfilter.h:287 [inline]
ip_local_deliver+0x1e9/0x750 net/ipv4/ip_input.c:256
dst_input include/net/dst.h:450 [inline]
ip_rcv_finish+0x823/0x2220 net/ipv4/ip_input.c:396
NF_HOOK include/linux/netfilter.h:287 [inline]
ip_rcv+0xa18/0x1284 net/ipv4/ip_input.c:492
__netif_receive_skb_core+0x2488/0x3680 net/core/dev.c:4628
__netif_receive_skb+0x2c/0x1e0 net/core/dev.c:4693
process_backlog+0x219/0x760 net/core/dev.c:5373
napi_poll net/core/dev.c:5771 [inline]
net_rx_action+0x7da/0x1980 net/core/dev.c:5837
__do_softirq+0x2e8/0xb17 kernel/softirq.c:284
run_ksoftirqd+0x86/0x100 kernel/softirq.c:645
smpboot_thread_fn+0x417/0x870 kernel/smpboot.c:164
kthread+0x345/0x410 kernel/kthread.c:240
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Cc: dccp@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/dccp/ccids/ccid3.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -624,9 +624,8 @@ static void ccid3_hc_rx_send_feedback(st
case CCID3_FBACK_PERIODIC:
delta = ktime_us_delta(now, hc->rx_tstamp_last_feedback);
if (delta <= 0)
- DCCP_BUG("delta (%ld) <= 0", (long)delta);
- else
- hc->rx_x_recv = scaled_div32(hc->rx_bytes_recv, delta);
+ delta = 1;
+ hc->rx_x_recv = scaled_div32(hc->rx_bytes_recv, delta);
break;
default:
return;

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