Re: [BUG] NULL pointer deref with rcutorture

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Sat, Jan 03, 2009 at 12:23:03AM +0530, Kamalesh Babulal wrote:
> * Paul E. McKenney <paulmck@linux.vnet.ibm.com> [2009-01-02 09:58:53]:
> 
> > On Fri, Jan 02, 2009 at 12:18:19PM +0100, Eric Sesterhenn wrote:
> > > Hi,
> > > 
> > > modprobing rcutorture and removing it again gives me the following oops:
> > 
> > This looks similar to something that Kamalesh ran into a few weeks ago.
> > 
> > Kamalesh, did the fixes for that make it to 2.6.28?
> > 
> > 							Thanx, Paul
> > 
> 
> Hi Paul,
> 
> 	The fix was available in linux-next from Dec 23 2008 (commit 392ddc32982a5c661dd90dd49a3cb37f1c68b782
> 'bio: add support for inlining a number of bio_vecs inside the bio') and it has be pushed for merger in 2.6.29.

Thank you, Kamalesh!

Eric, could you please try applying the above commit and see if the
problem reproduces?

							Thanx, Paul

> > > [  122.873859] rcu-torture:--- Start of test: nreaders=2 nfakewriters=4 stat_interval=0 verbose=0 test_no_idle_hz=0 shuffle_interval=3 stutter=5 irqreader=1
> > > [  162.987060] BUG: unable to handle kernel NULL pointer dereference at 00000000
> > > [  162.987194] IP: [<00000000>] 0x0
> > > [  162.987268] *pde = 00000000 
> > > [  162.987339] Oops: 0000 [#1] PREEMPT DEBUG_PAGEALLOC
> > > [  162.987499] last sysfs file: /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/resource
> > > [  162.987534] Modules linked in: [last unloaded: rcutorture]
> > > [  162.987667] 
> > > [  162.987699] Pid: 5091, comm: udevd Tainted: G        W  (2.6.28-04980-gb58602a-dirty #154) System Name
> > > [  162.987732] EIP: 0060:[<00000000>] EFLAGS: 00010246 CPU: 0
> > > [  162.987761] EIP is at 0x0
> > > [  162.987849] EAX: d0afcbf0 EBX: 00000000 ECX: c0160f5a EDX: 00000006
> > > [  162.987880] ESI: d0afcbf0 EDI: 0000001c EBP: c0b01fe0 ESP: c0b01fd4
> > > [  162.987910]  DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068
> > > [  162.987941] Process udevd (pid: 5091, ti=c0b01000 task=c8cc4100 task.ti=c8d20000)
> > > [  162.988027] Stack:
> > > [  162.988027]  c0160f61 00000200 00000001 c0b01ff8 c012a723 0000000a c8d20e4c 00000046
> > > [  162.988027]  c012a6b4 c8d20e5c c01042ce
> > > [  162.988027] Call Trace:
> > > [  162.988027]  [<c0160f61>] ? rcu_process_callbacks+0x65/0x79
> > > [  162.988027]  [<c012a723>] ? __do_softirq+0x6f/0xf6
> > > [  162.988027]  [<c012a6b4>] ? __do_softirq+0x0/0xf6
> > > [  162.988027]  <IRQ> <0> [<c012a631>] ? irq_exit+0x40/0x7c
> > > [  162.988027]  [<c0110b91>] ? smp_apic_timer_interrupt+0x68/0x73
> > > [  162.988027]  [<c0103521>] ? apic_timer_interrupt+0x2d/0x34
> > > [  162.988027]  [<c017af71>] ? unmap_vmas+0x308/0x47f
> > > [  162.988027]  [<c017afa2>] ? unmap_vmas+0x339/0x47f
> > > [  162.988027]  [<c0143db5>] ? trace_hardirqs_on_caller+0x17/0x15a
> > > [  162.988027]  [<c017e326>] ? exit_mmap+0x83/0x104
> > > [  162.988027]  [<c01244b8>] ? mmput+0x39/0x89
> > > [  162.988027]  [<c01278de>] ? exit_mm+0xc3/0xcb
> > > [  162.988027]  [<c0128b99>] ? do_exit+0x199/0x6d5
> > > [  162.988027]  [<c04e56b0>] ? trace_hardirqs_on_thunk+0xc/0x10
> > > [  162.988027]  [<c0129137>] ? do_group_exit+0x62/0x88
> > > [  162.988027]  [<c0129171>] ? sys_exit_group+0x14/0x16
> > > [  162.988027]  [<c0102ea1>] ? sysenter_do_call+0x12/0x31
> > > [  162.988027] Code:  Bad EIP value.
> > > [  162.988027] EIP: [<00000000>] 0x0 SS:ESP 0068:c0b01fd4
> > > [  162.990524] ---[ end trace 4eaa2a86a8e2da22 ]---
> > > [  162.990555] Kernel panic - not syncing: Fatal exception in interrupt
> > > 
> > > 
> > > Kernel is current -git with a unrelated
> > > networking patch (http://marc.info/?l=linux-netdev&m=123088641023335&w=2)
> > > 
> > > root@whiterabbit:/usr/src/linux# grep RCU .config
> > > # CONFIG_CLASSIC_RCU is not set
> > > # CONFIG_TREE_RCU is not set
> > > CONFIG_PREEMPT_RCU=y
> > > CONFIG_RCU_TRACE=y
> > > # CONFIG_TREE_RCU_TRACE is not set
> > > CONFIG_PREEMPT_RCU_TRACE=y
> > > CONFIG_RCU_TORTURE_TEST=m
> > > 
> > > Greetings, Eric
> > > --
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> 
> -- 
> Thanks & Regards,
> Kamalesh Babulal,
> Linux Technology Center,
> IBM, ISTL.