Re: [crash] BUG: unable to handle kernel NULL pointer dereferenceat 0000000000000370

From: Larry Finger
Date: Mon Jul 21 2008 - 15:43:49 EST

Ingo Molnar wrote:
* Larry Finger <Larry.Finger@xxxxxxxxxxxx> wrote:

Ingo Molnar wrote:
* Ian Schram <ischram@xxxxxxxxxx> wrote:

I was looking at this out of interest, but I'm in no way familiar with the code.
thanks Ian for the patch, i'll test it.

Note that it was whitespace damaged, find below a tidied up version of the patch that i've applied to tip/out-of-tree.

This patch may be needed to fix error handling in the hw_sim code, but I get the crash even with that code disabled. I'm currently bisecting to find the culprit.

ok. I just reactivated CONFIG_MAC80211_HWSIM, applied Ian's fix and the crash went away:

calling iwl4965_init+0x0/0x6c
iwl4965: Intel(R) Wireless WiFi Link 4965AGN driver for Linux, 1.3.27kd
iwl4965: Copyright(c) 2003-2008 Intel Corporation
initcall iwl4965_init+0x0/0x6c returned 0 after 10 msecs
calling init_mac80211_hwsim+0x0/0x31c
mac80211_hwsim: Initializing radio 0
PM: Adding info for No Bus:hwsim0
PM: Adding info for No Bus:phy0
PM: Adding info for No Bus:wmaster0
phy0: Failed to select rate control algorithm
phy0: Failed to initialize rate control algorithm
PM: Removing info for No Bus:wmaster0
PM: Removing info for No Bus:phy0
mac80211_hwsim: ieee80211_register_hw failed (-2)
PM: Removing info for No Bus:hwsim0
initcall init_mac80211_hwsim+0x0/0x31c returned -2 after 58 msecs
initcall init_mac80211_hwsim+0x0/0x31c returned with error code -2
calling dmfe_init_module+0x0/0xea
dmfe: Davicom DM9xxx net driver, version 1.36.4 (2002-01-17)
initcall dmfe_init_module+0x0/0xea returned 0 after 5 msecs

So at least as far as the init_mac80211_hwsim() deinit crash goes:

Tested-by: Ingo Molnar <mingo@xxxxxxx>

Yes, I'm chasing a distinct bug. The header for mine is

Jul 21 12:19:37 larrylap kernel: kernel BUG at net/core/dev.c:1328!
Jul 21 12:19:37 larrylap kernel: invalid opcode: 0000 [1] SMP
Jul 21 12:19:37 larrylap kernel: CPU 0
Jul 21 12:19:37 larrylap kernel: Modules linked in: af_packet rfkill_input nfs lockd nfs_acl sunrpc cpufreq_conservative cpu
freq_userspace cpufreq_powersave powernow_k8 fuse loop dm_mod arc4 ecb crypto_blkcipher b43 firmware_class rfkill mac80211 c
fg80211 snd_hda_intel snd_pcm snd_timer led_class snd k8temp input_polldev sr_mod soundcore button battery hwmon cdrom force
deth ac serio_raw ssb snd_page_alloc sg ehci_hcd sd_mod ohci_hcd usbcore edd fan thermal processor ext3 mbcache jbd pata_amd
ahci libata scsi_mod dock
Jul 21 12:19:37 larrylap kernel: Pid: 2057, comm: b43 Not tainted 2.6.26-Linus-git-05253-g14b395e #1
Jul 21 12:19:37 larrylap kernel: RIP: 0010:[<ffffffff8039ec4d>] [<ffffffff8039ec4d>] __netif_schedule+0x12/0x75
Jul 21 12:19:37 larrylap kernel: RSP: 0000:ffff8800b9ae1de0 EFLAGS: 00010246

With an invalid opcode, mine is likely due to stack corruption.

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