From d0af683407a26a4437d8fa6e283ea201f2ae8146 Mon Sep 17 00:00:00 2001 From: Ian Kumlien Date: Mon, 2 Jan 2017 09:18:35 +0100 Subject: [PATCH] flow_dissector: Update pptp handling to avoid null pointer deref. __skb_flow_dissect can be called with a skb or a data packet, either can be NULL. All calls seems to have been moved to __skb_header_pointer except the pptp handling which is still calling skb_header_pointer. skb_header_pointer will use skb->data and thus: [ 109.556866] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 109.557102] IP: [] __skb_flow_dissect+0xa88/0xce0 [ 109.557263] PGD 0 [ 109.557338] [ 109.557484] Oops: 0000 [#1] SMP [ 109.557562] Modules linked in: chaoskey [ 109.557783] CPU: 2 PID: 0 Comm: swapper/2 Not tainted 4.9.0 #79 [ 109.557867] Hardware name: Supermicro A1SRM-LN7F/LN5F/A1SRM-LN7F-2758, BIOS 1.0c 11/04/2015 [ 109.557957] task: ffff94085c27bc00 task.stack: ffffb745c0068000 [ 109.558041] RIP: 0010:[] [] __skb_flow_dissect+0xa88/0xce0 [ 109.558203] RSP: 0018:ffff94087fc83d40 EFLAGS: 00010206 [ 109.558286] RAX: 0000000000000130 RBX: ffffffff8975bf80 RCX: ffff94084fab6800 [ 109.558373] RDX: 0000000000000010 RSI: 000000000000000c RDI: 0000000000000000 [ 109.558460] RBP: 0000000000000b88 R08: 0000000000000000 R09: 0000000000000022 [ 109.558547] R10: 0000000000000008 R11: ffff94087fc83e04 R12: 0000000000000000 [ 109.558763] R13: ffff94084fab6800 R14: ffff94087fc83e04 R15: 000000000000002f [ 109.558979] FS: 0000000000000000(0000) GS:ffff94087fc80000(0000) knlGS:0000000000000000 [ 109.559326] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 109.559539] CR2: 0000000000000080 CR3: 0000000281809000 CR4: 00000000001026e0 [ 109.559753] Stack: [ 109.559957] 000000000000000c ffff94084fab6822 0000000000000001 ffff94085c2b5fc0 [ 109.560578] 0000000000000001 0000000000002000 0000000000000000 0000000000000000 [ 109.561200] 0000000000000000 0000000000000000 0000000000000000 0000000000000000 [ 109.561820] Call Trace: [ 109.562027] [ 109.562108] [] ? eth_get_headlen+0x7a/0xf0 [ 109.562522] [] ? igb_poll+0x96a/0xe80 [ 109.562737] [] ? net_rx_action+0x20b/0x350 [ 109.562953] [] ? __do_softirq+0xe8/0x280 [ 109.563169] [] ? irq_exit+0xaa/0xb0 [ 109.563382] [] ? do_IRQ+0x4b/0xc0 [ 109.563597] [] ? common_interrupt+0x7f/0x7f [ 109.563810] [ 109.563890] [] ? cpuidle_enter_state+0x130/0x2c0 [ 109.564304] [] ? cpuidle_enter_state+0x120/0x2c0 [ 109.564520] [] ? cpu_startup_entry+0x19f/0x1f0 [ 109.564737] [] ? start_secondary+0x12a/0x140 [ 109.564950] Code: 83 e2 20 a8 80 0f 84 60 01 00 00 c7 04 24 08 00 00 00 66 85 d2 0f 84 be fe ff ff e9 69 fe ff ff 8b 34 24 89 f2 83 c2 04 66 85 c0 <41> 8b 84 24 80 00 00 00 0f 49 d6 41 8d 31 01 d6 41 2b 84 24 84 [ 109.569959] RIP [] __skb_flow_dissect+0xa88/0xce0 [ 109.570245] RSP [ 109.570453] CR2: 0000000000000080 Fixes: ab10dccb1160 ("rps: Inspect PPTP encapsulated by GRE to get flow hash") Signed-off-by: Ian Kumlien Signed-off-by: David S. Miller --- net/core/flow_dissector.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c index d6447dc10371..fe4e1531976c 100644 --- a/net/core/flow_dissector.c +++ b/net/core/flow_dissector.c @@ -468,8 +468,9 @@ ip_proto_again: if (hdr->flags & GRE_ACK) offset += sizeof(((struct pptp_gre_header *)0)->ack); - ppp_hdr = skb_header_pointer(skb, nhoff + offset, - sizeof(_ppp_hdr), _ppp_hdr); + ppp_hdr = __skb_header_pointer(skb, nhoff + offset, + sizeof(_ppp_hdr), + data, hlen, _ppp_hdr); if (!ppp_hdr) goto out_bad; -- 2.20.1