Date:	Wed, 13 Oct 2010 18:36:04 -0400
From:	gvs@...os.net
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	netdev@...r.kernel.org, bugzilla-daemon@...zilla.kernel.org,
	bugme-daemon@...zilla.kernel.org,
	Michal Ostrowski <mostrows@...thlink.net>
Subject: Re: [Bugme-new] [Bug 20292] New: unable to handle kernel NULL pointer
 dereference in skb_dequeue

I had no problems getting it to work properly in 2.6.35.7. However, when
I booted back into rc7 I was unable to reproduce the problem. I believe
I was running multiple pppd's that failed to authenticate at the time
the bug occured.

I'll leave it running rc7 and see if everything stays stable.

gvs

On Wed, Oct 13, 2010 at 12:33:32PM -0700, Andrew Morton wrote:
> 
> (switched to email.  Please respond via emailed reply-to-all, not via the
> bugzilla web interface).
> 
> On Wed, 13 Oct 2010 19:24:53 GMT
> bugzilla-daemon@...zilla.kernel.org wrote:
> 
> > https://bugzilla.kernel.org/show_bug.cgi?id=20292
> > 
> >            Summary: unable to handle kernel NULL pointer dereference in
> >                     skb_dequeue
> >            Product: Networking
> >            Version: 2.5
> >     Kernel Version: 2.6.36-rc7
> 
> Thanks.  Do you know if this is a regression?  Did it work OK on 2.6.35?
> 
> >           Platform: All
> >         OS/Version: Linux
> >               Tree: Mainline
> >             Status: NEW
> >           Severity: blocking
> >           Priority: P1
> >          Component: Other
> >         AssignedTo: acme@...stprotocols.net
> >         ReportedBy: gvs@...os.net
> >         Regression: No
> > 
> > 
> > Created an attachment (id=33512)
> >  --> (https://bugzilla.kernel.org/attachment.cgi?id=33512)
> > Kernel config (gzipped)
> > 
> > I was trying to get pppoe working (the 'pon' command seemed to hang) and then
> > this happened:
> > 
> > Oct 13 20:57:07 bes kernel: BUG: unable to handle kernel NULL pointer
> > dereference at (null)
> > Oct 13 20:57:07 bes kernel: IP: [<c1241674>] skb_dequeue+0x24/0x40
> > Oct 13 20:57:07 bes kernel: *pde = 00000000
> > Oct 13 20:57:07 bes kernel: Oops: 0002 [#1]
> > Oct 13 20:57:07 bes kernel: last sysfs file:
> > /sys/devices/virtual/net/ppp0/uevent
> > Oct 13 20:57:07 bes kernel: Modules linked in: xt_TCPMSS xt_tcpmss xt_tcpudp
> > iptable_mangle pppoe pppox ppp_generic slhc cpufreq_conservative
> > cpufreq_userspace cpufreq_powersave fuse ipt_MASQUERADE iptable_nat nf_nat
> > nf_conntrack_ipv4 nf_defrag_ipv4 xt_state nf_conntrack iptable_filter ip_tables
> > x_tables loop sd_mod usb_storage usblp i2c_viapro uhci_hcd fan ehci_hcd button
> > i2c_core
> > Oct 13 20:57:07 bes kernel:
> > Oct 13 20:57:07 bes kernel: Pid: 5495, comm: pppd Not tainted 2.6.36-rc7 #12
> > VX800 /VX800
> > Oct 13 20:57:07 bes kernel: EIP: 0060:[<c1241674>] EFLAGS: 00010046 CPU: 0
> > Oct 13 20:57:07 bes kernel: EIP is at skb_dequeue+0x24/0x40
> > Oct 13 20:57:07 bes kernel: EAX: 00000000 EBX: 00000202 ECX: f6ba4cc0 EDX:
> > 00000000
> > Oct 13 20:57:07 bes kernel: ESI: f6c93bc0 EDI: f6adfee4 EBP: f6ade000 ESP:
> > f6adfe68
> > Oct 13 20:57:07 bes kernel: DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068
> > Oct 13 20:57:07 bes kernel: Process pppd (pid: 5495, ti=f6ade000 task=f70f2200
> > task.ti=f6ade000)
> > Oct 13 20:57:07 bes kernel: Stack:
> > Oct 13 20:57:07 bes kernel: f68836c4 c1243a94 f68836c0 f866825b 00000000
> > f72e4a00 f72e4a00 f86761cb
> > Oct 13 20:57:07 bes kernel: <0> f72e4a00 f8683c97 c143ea14 ffffffea c12ba92d
> > 00000286 f68f7d7c f6adfee4
> > Oct 13 20:57:07 bes kernel: <0> f68f7bfc 00000286 00000000 00000000 00000000
> > f68f7b9c f6adff68 f6adff64
> > Oct 13 20:57:07 bes kernel: Call Trace:
> > Oct 13 20:57:07 bes kernel: [<c1243a94>] ? skb_queue_purge+0x14/0x30
> > Oct 13 20:57:07 bes kernel: [<f866825b>] ? ppp_destroy_channel+0x1b/0x50
> > [ppp_generic]
> > Oct 13 20:57:07 bes kernel: [<f86761cb>] ? pppox_unbind_sock+0x1b/0x24 [pppox]
> > Oct 13 20:57:07 bes kernel: [<f8683c97>] ? pppoe_connect+0x87/0x4b0 [pppoe]
> > Oct 13 20:57:07 bes kernel: [<c12ba92d>] ? schedule_timeout+0xfd/0x150
> > Oct 13 20:57:07 bes kernel: [<c123d4d4>] ? sys_connect+0x84/0xd0
> > Oct 13 20:57:07 bes kernel: [<c10ba730>] ? do_lock_file_wait+0x30/0xf0
> > Oct 13 20:57:07 bes kernel: [<c10ba9f9>] ? fcntl_setlk+0x59/0x1b0
> > Oct 13 20:57:07 bes kernel: [<c123e5a4>] ? sys_socketcall+0x294/0x2c0
> > Oct 13 20:57:07 bes kernel: [<c1002a10>] ? sysenter_do_call+0x12/0x26
> > Oct 13 20:57:07 bes kernel: Code: 81 a8 00 00 00 5b c3 53 9c 5b fa 8b 08 39 c8
> > 74 25 85 c9 74 1b 83 68 08 01 8b 11 8b 41 04 c7 01 00 00 00 00 c7 41 04 00 00
> > 00 00 <89> 10 89 42 04 53 9d 89 c8 5b c3 31 c9 eb f6 8d b6 00 00 00 00
> > Oct 13 20:57:07 bes kernel: EIP: [<c1241674>] skb_dequeue+0x24/0x40 SS:ESP
> > 0068:f6adfe68
> > Oct 13 20:57:07 bes kernel: CR2: 0000000000000000
> > Oct 13 20:57:07 bes kernel: ---[ end trace 4914adf67d1ace25 ]---
> > 
> > Oct 13 20:57:30 bes kernel: BUG: unable to handle kernel NULL pointer
> > dereference at (null)
> > Oct 13 20:57:30 bes kernel: IP: [<c1241674>] skb_dequeue+0x24/0x40
> > Oct 13 20:57:30 bes kernel: *pde = 00000000
> > Oct 13 20:57:30 bes kernel: Oops: 0002 [#2]
> > Oct 13 20:57:30 bes kernel: last sysfs file:
> > /sys/devices/virtual/net/ppp0/uevent
> > Oct 13 20:57:30 bes kernel: Modules linked in: xt_TCPMSS xt_tcpmss xt_tcpudp
> > iptable_mangle pppoe pppox ppp_generic slhc cpufreq_conservative
> > cpufreq_userspace cpufreq_powersave fuse ipt_MASQUERADE iptable_nat nf_nat
> > nf_conntrack_ipv4 nf_defrag_ipv4 xt_state nf_conntrack iptable_filter ip_tables
> > x_tables loop sd_mod usb_storage usblp i2c_viapro uhci_hcd fan ehci_hcd button
> > i2c_core
> > Oct 13 20:57:30 bes kernel:
> > Oct 13 20:57:30 bes kernel: Pid: 5445, comm: pppd Tainted: G      D    
> > 2.6.36-rc7 #12 VX800 /VX800
> > Oct 13 20:57:30 bes kernel: EIP: 0060:[<c1241674>] EFLAGS: 00010046 CPU: 0
> > Oct 13 20:57:30 bes kernel: EIP is at skb_dequeue+0x24/0x40
> > Oct 13 20:57:30 bes kernel: EAX: 00000000 EBX: 00000202 ECX: f6ae7200 EDX:
> > 00000000
> > Oct 13 20:57:30 bes kernel: ESI: f6c99080 EDI: f7161ee4 EBP: f7160000 ESP:
> > f7161e68
> > Oct 13 20:57:30 bes kernel: DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068
> > Oct 13 20:57:30 bes kernel: Process pppd (pid: 5445, ti=f7160000 task=f7107280
> > task.ti=f7160000)
> > Oct 13 20:57:30 bes kernel: Stack:
> > Oct 13 20:57:30 bes kernel: f6883344 c1243a94 f6883340 f866825b 00000000
> > f72e4c00 f72e4c00 f86761cb
> > Oct 13 20:57:30 bes kernel: <0> f72e4c00 f8683c97 c143ea14 ffffffea c12ba92d
> > 00000286 f68f73bc f7161ee4
> > Oct 13 20:57:30 bes kernel: <0> f68f753c 00000286 00000000 00000000 00000000
> > f68f759c f7161f68 f7161f64
> > Oct 13 20:57:30 bes kernel: [<c1243a94>] ? skb_queue_purge+0x14/0x30
> > Oct 13 20:57:30 bes kernel: [<f866825b>] ? ppp_destroy_channel+0x1b/0x50
> > [ppp_generic]
> > Oct 13 20:57:30 bes kernel: [<f86761cb>] ? pppox_unbind_sock+0x1b/0x24 [pppox]
> > Oct 13 20:57:30 bes kernel: [<f8683c97>] ? pppoe_connect+0x87/0x4b0 [pppoe]
> > Oct 13 20:57:30 bes kernel: [<c12ba92d>] ? schedule_timeout+0xfd/0x150
> > Oct 13 20:57:30 bes kernel: [<c123d4d4>] ? sys_connect+0x84/0xd0
> > Oct 13 20:57:30 bes kernel: [<c10ba730>] ? do_lock_file_wait+0x30/0xf0
> > Oct 13 20:57:30 bes kernel: [<c10ba9f9>] ? fcntl_setlk+0x59/0x1b0
> > Oct 13 20:57:30 bes kernel: [<c123e5a4>] ? sys_socketcall+0x294/0x2c0
> > Oct 13 20:57:30 bes kernel: [<c1002a10>] ? sysenter_do_call+0x12/0x26
> > Oct 13 20:57:30 bes kernel: Code: 81 a8 00 00 00 5b c3 53 9c 5b fa 8b 08 39 c8
> > 74 25 85 c9 74 1b 83 68 08 01 8b 11 8b 41 04 c7 01 00 00 00 00 c7 41 04 00 00
> > 00 00 <89> 10 89 42 04 53 9d 89 c8 5b c3 31 c9 eb f6 8d b6 00 00 00 00
> > Oct 13 20:57:30 bes kernel: EIP: [<c1241674>] skb_dequeue+0x24/0x40 SS:ESP
> > 0068:f7161e68
> > Oct 13 20:57:30 bes kernel: CR2: 0000000000000000
> > Oct 13 20:57:30 bes kernel: ---[ end trace 4914adf67d1ace26 ]---
> > Oct 13 20:57:30 bes kernel: ------------[ cut here ]------------
> > Oct 13 20:57:30 bes kernel: WARNING: at kernel/softirq.c:143
> > local_bh_enable+0x60/0x90()
> > Oct 13 20:57:30 bes kernel: Hardware name: VX800
> > Oct 13 20:57:30 bes kernel: Modules linked in: xt_TCPMSS xt_tcpmss xt_tcpudp
> > iptable_mangle pppoe pppox ppp_generic slhc cpufreq_conservative
> > cpufreq_userspace cpufreq_powersave fuse ipt_MASQUERADE iptable_nat nf_nat
> > nf_conntrack_ipv4 nf_defrag_ipv4 xt_state nf_conntrack iptable_filter ip_tables
> > x_tables loop sd_mod usb_storage usblp i2c_viapro uhci_hcd fan ehci_hcd button
> > i2c_core
> > Oct 13 20:57:30 bes kernel: Pid: 5445, comm: pppd Tainted: G      D    
> > 2.6.36-rc7 #12
> > Oct 13 20:57:30 bes kernel: Call Trace:
> > Oct 13 20:57:30 bes kernel: [<c1028640>] ? local_bh_enable+0x60/0x90
> > Oct 13 20:57:30 bes kernel: [<c1028640>] ? local_bh_enable+0x60/0x90
> > Oct 13 20:57:30 bes kernel: [<c1023a1e>] ? warn_slowpath_common+0x7e/0xc0
> > Oct 13 20:57:30 bes kernel: [<c1028640>] ? local_bh_enable+0x60/0x90
> > Oct 13 20:57:30 bes kernel: [<c1023a7b>] ? warn_slowpath_null+0x1b/0x20
> > Oct 13 20:57:30 bes kernel: [<c1028640>] ? local_bh_enable+0x60/0x90
> > Oct 13 20:57:30 bes kernel: [<c12a5bb5>] ? unix_release_sock+0x45/0x1f0
> > Oct 13 20:57:30 bes kernel: [<c123dc4a>] ? sock_release+0x1a/0x80
> > Oct 13 20:57:30 bes kernel: [<c123dcbf>] ? sock_close+0xf/0x30
> > Oct 13 20:57:30 bes kernel: [<c1089cd9>] ? fput+0xb9/0x200
> > Oct 13 20:57:30 bes kernel: [<c1086f7e>] ? filp_close+0x3e/0x70
> > Oct 13 20:57:30 bes kernel: [<c10254b2>] ? put_files_struct+0x62/0xb0
> > Oct 13 20:57:30 bes kernel: [<c1026c47>] ? do_exit+0x567/0x630
> > Oct 13 20:57:30 bes kernel: [<c12ba037>] ? printk+0x17/0x20
> > Oct 13 20:57:30 bes kernel: [<c1005477>] ? oops_end+0x87/0x90
> > Oct 13 20:57:30 bes kernel: [<c12ba037>] ? printk+0x17/0x20
> > Oct 13 20:57:30 bes kernel: [<c10194a2>] ? no_context+0xc2/0x160
> > Oct 13 20:57:30 bes kernel: [<c10195a5>] ? __bad_area_nosemaphore+0x65/0x180
> > Oct 13 20:57:30 bes kernel: [<c1249a3b>] ? dev_txq_stats_fold+0x8b/0xf0
> > Oct 13 20:57:30 bes kernel: [<c117dc80>] ? __nla_reserve+0x40/0x60
> > Oct 13 20:57:30 bes kernel: [<c1255c33>] ? rtnl_fill_ifinfo+0x413/0x8d0
> > Oct 13 20:57:30 bes kernel: [<c101971a>] ? bad_area+0x3a/0x50
> > Oct 13 20:57:30 bes kernel: [<c1019b8e>] ? do_page_fault+0x33e/0x390
> > Oct 13 20:57:30 bes kernel: [<c101e6ab>] ? wakeup_preempt_entity+0x3b/0xa0
> > Oct 13 20:57:30 bes kernel: [<c101e79a>] ? check_preempt_wakeup+0x8a/0xe0
> > Oct 13 20:57:30 bes kernel: [<c1097675>] ? pollwake+0x65/0x80
> > Oct 13 20:57:30 bes kernel: [<c1021170>] ? default_wake_function+0x0/0x10
> > Oct 13 20:57:30 bes kernel: [<c1019850>] ? do_page_fault+0x0/0x390
> > Oct 13 20:57:30 bes kernel: [<c12bbcf0>] ? error_code+0x58/0x60
> > Oct 13 20:57:30 bes kernel: [<c1019850>] ? do_page_fault+0x0/0x390
> > Oct 13 20:57:30 bes kernel: [<c1241674>] ? skb_dequeue+0x24/0x40
> > Oct 13 20:57:30 bes kernel: [<c1243a94>] ? skb_queue_purge+0x14/0x30
> > Oct 13 20:57:30 bes kernel: [<f866825b>] ? ppp_destroy_channel+0x1b/0x50
> > [ppp_generic]
> > Oct 13 20:57:30 bes kernel: [<f86761cb>] ? pppox_unbind_sock+0x1b/0x24 [pppox]
> > Oct 13 20:57:30 bes kernel: [<f8683c97>] ? pppoe_connect+0x87/0x4b0 [pppoe]
> > Oct 13 20:57:30 bes kernel: [<c12ba92d>] ? schedule_timeout+0xfd/0x150
> > Oct 13 20:57:30 bes kernel: [<c123d4d4>] ? sys_connect+0x84/0xd0
> > Oct 13 20:57:30 bes kernel: [<c10ba730>] ? do_lock_file_wait+0x30/0xf0
> > Oct 13 20:57:30 bes kernel: [<c10ba9f9>] ? fcntl_setlk+0x59/0x1b0
> > Oct 13 20:57:30 bes kernel: [<c123e5a4>] ? sys_socketcall+0x294/0x2c0
> > Oct 13 20:57:30 bes kernel: [<c1002a10>] ? sysenter_do_call+0x12/0x26
> > Oct 13 20:57:30 bes kernel: ---[ end trace 4914adf67d1ace27 ]---
> > 
> > Some other information:
> > /proc/version:
> > Linux version 2.6.36-rc7 (root@bes) (gcc version 4.3.2 (Debian 4.3.2-1.1) ) #12
> > Sun Oct 10 21:12:58 CEST 2010
> > 
> > ver_linux:
> > Linux bes 2.6.36-rc7 #12 Sun Oct 10 21:12:58 CEST 2010 i686 GNU/Linux
> > 
> > Gnu C                  4.4.5
> > Gnu make               3.81
> > binutils               2.20.1
> > util-linux             2.17.2
> > mount                  support
> > module-init-tools      3.12
> > e2fsprogs              1.41.12
> > PPP                    2.4.5
> > Linux C Library        2.11.2
> > Dynamic linker (ldd)   2.11.2
> > Procps                 3.2.8
> > Net-tools              1.60
> > Console-tools          0.2.3
> > Sh-utils               8.5
> > Modules Loaded         cpufreq_conservative cpufreq_userspace cpufreq_powersave
> > fuse ppp_generic slhc ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4
> > nf_defrag_ipv4 xt_state nf_conntrack iptable_filter ip_tables x_tables loop
> > sd_mod usb_storage usblp i2c_viapro uhci_hcd fan i2c_core ehci_hcd button
> > 
> > cpuinfo:
> > processor       : 0
> > vendor_id       : CentaurHauls
> > cpu family      : 6
> > model           : 13
> > model name      : VIA Eden Processor 1600MHz
> > stepping        : 0
> > cpu MHz         : 800.000
> > cache size      : 128 KB
> > fdiv_bug        : no
> > hlt_bug         : no
> > f00f_bug        : no
> > coma_bug        : no
> > fpu             : yes
> > fpu_exception   : yes
> > cpuid level     : 1
> > wp              : yes
> > flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge cmov pat
> > clflush acpi mmx fxsr sse sse2 tm nx pni est tm2 xtpr rng rng_en ace ace_en
> > ace2 ace2_en phe phe_en pmm pmm_en
> > bogomips        : 1599.76
> > clflush size    : 64
> > cache_alignment : 64
> > address sizes   : 36 bits physical, 32 bits virtual
> > power management:
> > 
> > If anything else is needed I'd be happy to assist.
> > 
> 
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