linux-kernel - Re: v2.6.31-rc6: BUG: unable to handle kernel NULL pointer dereference at 0000000000000008

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Message-ID: <m1skfnggrb.fsf@fess.ebiederm.org>
Date:	Wed, 19 Aug 2009 23:07:36 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	<linux-kernel@...r.kernel.org>
Cc:	x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: Re: v2.6.31-rc6: BUG: unable to handle kernel NULL pointer dereference at 0000000000000008


ebiederm@...ssion.com (Eric W. Biederman) writes:

> I'm not certain who I should route this too, but I just had 2.6.31-rc6
> fall over on me.  I don't know how reproducible this will be but
> I have a full crash dump if someone is interested in looking into this.

Looks like I was wrong.  This is appears trivial to reproduce,
I have just reproduced it two more times in a row.  I think
the problem is pty related.

I was looking into a change in behavior on 2.6.31-rc6 where
data was being lost, and it appears one variant of my test program
kills the kernel.

The following program run as an unprivileged user causes a kernel
panic in about a minute:

aka

while :; do ./KernelTtyTest ; done


I'm not certain where to start digging into this beyond that.

Eric



View attachment "KernelTtyTest.c" of type "text/x-csrc" (5331 bytes)




>
> Eric
>
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
> IP: [<ffffffff8105be8b>] run_timer_softirq+0x13a/0x1fa
> PGD 0 
> Thread overran stack, or stack corrupted
> Oops: 0002 [#1] SMP 
> last sysfs file: /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq
> CPU 0 
> Modules linked in: veth macvlan nfsd lockd nfs_acl auth_rpcgss exportfs sco bridge stp bnep l2cap bluetooth sunrpc ipv6 cpufreq_ondemand acpi_cpufreq freq_table ext4 jbd2 crc16 dm_mirror dm_region_hash dm_log dm_multipath dm_mod uinput kvm_intel kvm fuse xt_multiport iptable_nat ip_tables nf_nat x_tables nf_conntrack_ipv4 nf_conntrack nf_defrag_ipv4 tun 8021q ixgbe iTCO_wdt iTCO_vendor_support i2c_i801 mdio e1000e pcspkr serio_raw sg ata_generic pata_acpi ata_piix libata sd_mod scsi_mod ext3 jbd mbcache uhci_hcd ohci_hcd ehci_hcd i915 drm i2c_algo_bit i2c_core video output [last unloaded: microcode]
> Pid: 0, comm: swapper Not tainted 2.6.31-rc6-172084.2009.AroraKernelBeta.fc11.x86_64 #1 PDSBM
> RIP: 0010:[<ffffffff8105be8b>]  [<ffffffff8105be8b>] run_timer_softirq+0x13a/0x1fa
> RSP: 0018:ffff8800017cfe30  EFLAGS: 00010006
> RAX: ffff8800365b2928 RBX: ffffffff81744e40 RCX: 0000000000000000
> RDX: ffff8800017cfe50 RSI: 0000000000000246 RDI: 0000000000000000
> RBP: ffff8800017cfea0 R08: ffff8800017d8c00 R09: ffff8800017cff08
> R10: 6b40fbe55cdd76b4 R11: ffffffff81744e40 R12: ffff8800017cfe50
> R13: 0000000000000000 R14: ffffffff81746658 R15: ffffffff81746258
> FS:  0000000000000000(0000) GS:ffff8800017cc000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
> CR2: 0000000000000008 CR3: 0000000001001000 CR4: 00000000000026f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Process swapper (pid: 0, threadinfo ffffffff815b2000, task ffffffff8153f020)
> Stack:
>  6b40fbe55cdd76b4 ffff880000000100 ffffffff81746a58 ffffffff81745e58
> <0> ffff8800365b2928 ffff8800abcd6128 ffffffff81023733 6b40fbe55cdd76b4
> <0> 6b40fbe55cdd76b4 0000000000000008 0000000000000001 0000000000000100
> Call Trace:
>  <IRQ> 
>  [<ffffffff81023733>] ? lapic_next_event+0x23/0x3b
>  [<ffffffff81056893>] __do_softirq+0xe7/0x1cd
>  [<ffffffff8100cfac>] call_softirq+0x1c/0x28
>  [<ffffffff8100e8e5>] do_softirq+0x51/0xae
>  [<ffffffff810564c6>] irq_exit+0x52/0xa3
>  [<ffffffff81024080>] smp_apic_timer_interrupt+0x94/0xb9
>  [<ffffffff8100c973>] apic_timer_interrupt+0x13/0x20
>  <EOI> 
>  [<ffffffff810143f2>] ? mwait_idle+0x9b/0xcc
>  [<ffffffff81014394>] ? mwait_idle+0x3d/0xcc
>  [<ffffffff8100ad4f>] ? enter_idle+0x33/0x49
>  [<ffffffff8100ae15>] ? cpu_idle+0xb0/0xf3
>  [<ffffffff81391c75>] ? rest_init+0x79/0x8f
>  [<ffffffff815bbf8e>] ? start_kernel+0x3dc/0x3fd
>  [<ffffffff815bb2b4>] ? x86_64_start_reservations+0xbb/0xd6
>  [<ffffffff815bb3d4>] ? x86_64_start_kernel+0x105/0x128
> Code: 49 8b 54 1d 20 48 89 55 b8 4c 89 22 49 89 44 1d 20 49 89 44 1d 18 eb 7e 4c 8b 68 18 48 8b 78 20 48 89 43 08 48 8b 08 48 8b 50 08 <48> 89 51 08 48 89 0a 48 c7 40 08 00 02 20 00 48 c7 00 00 00 00 
> RIP  [<ffffffff8105be8b>] run_timer_softirq+0x13a/0x1fa
>  RSP <ffff8800017cfe30>
> CR2: 0000000000000008