Message-ID: <452968.10877.qm@web52007.mail.re2.yahoo.com>
Date:	Mon, 12 Jul 2010 13:55:35 -0700 (PDT)
From:	Doug Kehn <rdkehn@...oo.com>
To:	netdev@...r.kernel.org
Subject: Kernel Oops in neighbour.c 2.6.26.8

Hi All,

I know my kernel version is old.  I'm working on an embedded system and updating to a newer kernel is time consuming.  Having said that, there are not that many differences in neighbour.c between 2.6.26.8 and the newer kernel revisions.

The Oops (included below) only occurs when configuring DMVPN (GRE + openNHRP) and a GRE Remote address is configured.  I found and included the neighbour.c patch outlined in
http://web.archiveorange.com/archive/v/iRKxruZnSerMcYadyaYq.  This patch did not eliminate the Oops.  The Oops I observed was in neigh_update_hhs. neigh->dev->header_ops is NULL thus the line

void (*update)(struct hh_cache*, const struct net_device*, const unsigned char *)
= neigh->dev->header_ops->cache_update;

causes the Oops.  The dev associated with the NULL header_ops was the GRE interface.  The following patch guards against the possibility that headers_ops is NULL.

--- neighbour.c.old	2010-07-12 15:29:24.000000000 -0500
+++ neighbour.c	2010-07-12 15:32:28.000000000 -0500
@@ -945,7 +945,10 @@
 {
 	struct hh_cache *hh;
 	void (*update)(struct hh_cache*, const struct net_device*, const unsigned char *)
-		= neigh->dev->header_ops->cache_update;
+		= NULL;
+
+	if (neigh->dev->header_ops)
+		update = neigh->dev->header_ops->cache_update;
 
 	if (update) {
 		for (hh = neigh->hh; hh; hh = hh->hh_next) {

I'm not sure if the above patch is the proper fix.  Since neigh_update_hhs in newer kernels is identical to 2.6.26.8, I thought I'd post my findings and solicit feedback.

Regards,
...doug


Unable to handle kernel NULL pointer dereference at virtual address 00000010
pgd = c745c000
[00000010] *pgd=07fe6031, *pte=00000000, *ppte=00000000
Internal error: Oops: 17 [#1]
Modules linked in: ppp_synctty ppp_async ppp_generic crc_ccitt slhc sierra md5 e
cb arc4 authenc xfrm4_tunnel xfrm_user tunnel4 ipcomp deflate ah4 esp4 aead cbc 
hmac sha1_generic des_generic aes_generic cryptomgr crypto_null crypto_blkcipher
 crypto_hash crypto_algapi af_key ipt_MASQUERADE xt_state xt_mac xt_tcpudp xt_mu
ltiport xt_dscp xt_CLASSIFY xt_DSCP xt_MARK iptable_mangle iptable_nat nf_nat xt
_conntrack nf_conntrack_ipv4 nf_conntrack iptable_filter ip_tables x_tables usbs
erial ehci_hcd usbcore spidev ixp4xx_spi ssp rtc_s35390a rtc_core i2c_gpio i2c_a
lgo_bit i2c_dev i2c_core ip_gre 8021q bridge ks8842_pci ixp4xx_eth ixp4xx_qmgr i
xp4xx_npe llc firmware_class ctdfs_irq ctdfs_ioreset ctdfs_cmb ctdfs_wdt ctdfs_b
eep ctdfs_reedswitch ctdfs_cpld ctdfs
CPU: 0    Not tainted  (2.6.26.8 #14)
PC is at neigh_update+0x1f8/0x3bc
LR is at 0x3f5840d4
pc : [<c016dca8>]    lr : [<3f5840d4>]    psr: 40000013
sp : c7449c38  ip : 0000001c  fp : c7449c6c
r10: c75457c4  r9 : 80000001  r8 : 00000040
r7 : c7541028  r6 : 00000002  r5 : c75457a0  r4 : c75457c4
r3 : 00000000  r2 : 00000000  r1 : c754102c  r0 : c75457c4
Flags: nZcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
Control: 000039ff  Table: 0745c000  DAC: 00000015
Process opennhrp (pid: 1110, stack limit = 0xc7448260)
Stack: (0xc7449c38 to 0xc744a000)
9c20:                                                       c7412000 00000000 
9c40: 00000040 c75457a0 c026b4f0 c7541020 c7412000 c7541000 c7541028 c7541010 
9c60: c7449cb0 c7449c70 c016eacc c016dabc 00000000 00000000 c754101c c7541024 
9c80: 00000000 00000000 0000002c c7541000 0000000c 00000002 00000003 fffffffc 
9ca0: c7c32ba0 c7449ce4 c7449cb4 c0170a6c c016e8ec 22222222 c7f1a0a0 c7541000 
9cc0: c7f1a0a0 c0170880 c7449d1c c7443600 00000000 00000000 c7449d00 c7449ce8 
9ce0: c017c460 c017088c c7f1a0a0 0000002c c7f1a0a0 c7449d14 c7449d04 c0170870 
9d00: c017c418 c7c37e00 c7449d48 c7449d18 c017beec c0170858 0000002c 7fffffff 
9d20: 00000000 c7f1a0a0 c7443600 c7449f58 c7838ce0 c7449e1c 00000000 c7449d94 
9d40: c7449d4c c017c1f8 c017bcd8 c7f1a5e0 0000002c 00000000 00000456 00000000 
9d60: 00000000 00000000 00000000 c7da4640 c7449f58 c7449d98 0000002c c7449ef8 
9d80: 00000000 00000008 c7449e74 c7449d98 c015a31c c017bfa0 00000000 c7541200 
9da0: 00000000 00000001 ffffffff 00000000 00000000 00000000 00000000 00000000 
9dc0: c7da4640 00000000 00000000 c7449e3c c7da4640 c004b89c c7449dd8 c7449dd8 
9de0: c740d005 0000004f c7449e1c 00000000 00000000 0000004f 00000456 00000000 
9e00: 00000000 00000000 00000000 c7449e2c 00000000 c7449eac c7f861a0 00000001 
9e20: c7449e60 c7449ef8 0000002c c7838ce0 c7449ef8 c7449d58 c7449f58 c7449e78 
9e40: 00000128 c7449ef8 c7449ef8 00000008 00000000 c7449f58 c0161f74 c7449f38 
9e60: 00000000 c7838ce0 c7449fa4 c7449e78 c015a4ec c015a278 00100000 00000000 
9e80: 00000000 c7449eac c7449f30 c7449f80 fffffdee c7449f58 c7449ea8 c007c1f8 
9ea0: c0159130 00000000 00000000 c0086ed0 c008631c 00000000 00000001 ffffffff 
9ec0: c7f861a0 00000000 00000000 00000000 00000000 c7da4640 00000000 00000000 
9ee0: c7c0c320 c7da4640 c004b89c c7449eec c7449eec 00000000 bedcfa38 00000000 
9f00: c0025fd4 c7449f2c 00000024 0000004f c7448000 0000000f 00000000 00000003 
9f20: 0000000b 00000000 00000000 c78042e4 00000002 c78041e4 0000004f c7449f80 
9f40: c7449f78 00000000 0000000d 000000ae c0020c44 c7449fa4 c7449e78 0000000c 
9f60: c7449ef8 00000001 00000000 00000000 00000000 00000000 ffffff97 000392d0 
9f80: bedcf9cc bedcfcd4 00000128 c0020c44 c7448000 0000934c 00000000 c7449fa8 
9fa0: c0020aa0 c015a348 000392d0 bedcf9cc 00000008 bedcf938 00000000 00000008 
9fc0: 000392d0 bedcf9cc bedcfcd4 bedcfc50 00000002 0001022c 0000934c bedcf978 
9fe0: 000290c8 bedcf920 0002148c 4008ca98 00000010 00000008 00000000 00000000 
Backtrace: 
[<c016dab0>] (neigh_update+0x0/0x3bc) from [<c016eacc>] (neigh_add+0x1ec/0x278)
[<c016e8e0>] (neigh_add+0x0/0x278) from [<c0170a6c>] (rtnetlink_rcv_msg+0x1ec/0x
228)
[<c0170880>] (rtnetlink_rcv_msg+0x0/0x228) from [<c017c460>] (netlink_rcv_skb+0x
54/0xb8)
[<c017c40c>] (netlink_rcv_skb+0x0/0xb8) from [<c0170870>] (rtnetlink_rcv+0x24/0x
34)
 r6:c7f1a0a0 r5:0000002c r4:c7f1a0a0
[<c017084c>] (rtnetlink_rcv+0x0/0x34) from [<c017beec>] (netlink_unicast+0x220/0
x2c8)
 r4:c7c37e00
[<c017bccc>] (netlink_unicast+0x0/0x2c8) from [<c017c1f8>] (netlink_sendmsg+0x26
4/0x278)
[<c017bf94>] (netlink_sendmsg+0x0/0x278) from [<c015a31c>] (sock_sendmsg+0xb0/0x
d0)
[<c015a26c>] (sock_sendmsg+0x0/0xd0) from [<c015a4ec>] (sys_sendmsg+0x1b0/0x20c)
 r6:c7838ce0 r5:00000000 r4:c7449f38
[<c015a33c>] (sys_sendmsg+0x0/0x20c) from [<c0020aa0>] (ret_fast_syscall+0x0/0x2
c)
Code: e5d320f0 ebfe51d7 e595300c e59330b0 (e5937010) 
Kernel panic - not syncing: Fatal exception in interrupt



      
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