From 3feec9095d12e311b7d4eb7fe7e5dfa75d4a72a5 Mon Sep 17 00:00:00 2001 From: James Chapman Date: Tue, 16 Mar 2010 06:46:31 +0000 Subject: [PATCH] l2tp: Fix oops in pppol2tp_xmit When transmitting L2TP frames, we derive the outgoing interface's UDP checksum hardware assist capabilities from the tunnel dst dev. This can sometimes be NULL, especially when routing protocols are used and routing changes occur. This patch just checks for NULL dst or dev pointers when checking for netdev hardware assist features. BUG: unable to handle kernel NULL pointer dereference at 0000000c IP: [] pppol2tp_xmit+0x341/0x4da [pppol2tp] *pde = 00000000 Oops: 0000 [#1] SMP last sysfs file: /sys/class/net/lo/operstate Modules linked in: pppol2tp pppox ppp_generic slhc ipv6 dummy loop snd_hda_codec_atihdmi snd_hda_intel snd_hda_codec snd_pcm snd_timer snd soundcore snd_page_alloc evdev psmouse serio_raw processor button i2c_piix4 i2c_core ati_agp agpgart pcspkr ext3 jbd mbcache sd_mod ide_pci_generic atiixp ide_core ahci ata_generic floppy ehci_hcd ohci_hcd libata e1000e scsi_mod usbcore nls_base thermal fan thermal_sys [last unloaded: scsi_wait_scan] Pid: 0, comm: swapper Not tainted (2.6.32.8 #1) EIP: 0060:[] EFLAGS: 00010297 CPU: 3 EIP is at pppol2tp_xmit+0x341/0x4da [pppol2tp] EAX: 00000000 EBX: f64d1680 ECX: 000005b9 EDX: 00000000 ESI: f6b91850 EDI: f64d16ac EBP: f6a0c4c0 ESP: f70a9cac DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 Process swapper (pid: 0, ti=f70a8000 task=f70a31c0 task.ti=f70a8000) Stack: 000005a9 000005b9 f734c400 f66652c0 f7352e00 f67dc800 00000000 f6b91800 <0> 000005a3 f70ef6c4 f67dcda9 000005a3 f89b192e 00000246 000005a3 f64d1680 <0> f63633e0 f6363320 f64d1680 f65a7320 f65a7364 f65856c0 f64d1680 f679f02f Call Trace: [] ? ppp_push+0x459/0x50e [ppp_generic] [] ? ppp_xmit_process+0x3b6/0x430 [ppp_generic] [] ? ppp_start_xmit+0x10d/0x120 [ppp_generic] [] ? dev_hard_start_xmit+0x21f/0x2b2 [] ? sch_direct_xmit+0x48/0x10e [] ? dev_queue_xmit+0x263/0x3a6 [] ? ip_finish_output+0x1f7/0x221 [] ? ip_forward_finish+0x2e/0x30 [] ? ip_rcv_finish+0x295/0x2a9 [] ? netif_receive_skb+0x3e9/0x404 [] ? e1000_clean_rx_irq+0x253/0x2fc [e1000e] [] ? e1000_clean+0x63/0x1fc [e1000e] [] ? sched_clock_local+0x15/0x11b [] ? net_rx_action+0x96/0x195 [] ? __do_softirq+0xaa/0x151 [] ? do_softirq+0x31/0x3c [] ? irq_exit+0x26/0x58 [] ? do_IRQ+0x78/0x89 [] ? common_interrupt+0x29/0x30 [] ? native_safe_halt+0x2/0x3 [] ? default_idle+0x55/0x75 [] ? c1e_idle+0xd2/0xd5 [] ? cpu_idle+0x46/0x62 Code: 8d 45 08 f0 ff 45 08 89 6b 08 c7 43 68 7e fb 9c f8 8a 45 24 83 e0 0c 3c 04 75 09 80 63 64 f3 e9 b4 00 00 00 8b 43 18 8b 4c 24 04 <8b> 40 0c 8d 79 11 f6 40 44 0e 8a 43 64 75 51 6a 00 8b 4c 24 08 EIP: [] pppol2tp_xmit+0x341/0x4da [pppol2tp] SS:ESP 0068:f70a9cac CR2: 000000000000000c Signed-off-by: James Chapman Signed-off-by: David S. Miller --- drivers/net/pppol2tp.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/net/pppol2tp.c b/drivers/net/pppol2tp.c index 9fbb2eba9a06..5861ee9599a2 100644 --- a/drivers/net/pppol2tp.c +++ b/drivers/net/pppol2tp.c @@ -1180,7 +1180,8 @@ static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb) /* Calculate UDP checksum if configured to do so */ if (sk_tun->sk_no_check == UDP_CSUM_NOXMIT) skb->ip_summed = CHECKSUM_NONE; - else if (!(skb_dst(skb)->dev->features & NETIF_F_V4_CSUM)) { + else if ((skb_dst(skb) && skb_dst(skb)->dev) && + (!(skb_dst(skb)->dev->features & NETIF_F_V4_CSUM))) { skb->ip_summed = CHECKSUM_COMPLETE; csum = skb_checksum(skb, 0, udp_len, 0); uh->check = csum_tcpudp_magic(inet->inet_saddr, -- 2.20.1