From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Morton <akpm@osdl.org>
Subject: Re: 2.6.17-mm3 -- NULL pointer dereference at virtual address
 00000020 / EIP is at prism2_registers_proc_read+0x22/0x2ff [hostap_cs]
Date: Wed, 28 Jun 2006 17:08:09 -0700
Message-ID: <20060628170809.374cafcf.akpm@osdl.org>
References: <a44ae5cd0606281634o45795e89y8789e670448f52e3@mail.gmail.com>
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Cc: linux-kernel@vger.kernel.org,
	"John W. Linville" <linville@tuxdriver.com>, netdev@vger.kernel.org
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To: "Miles Lane" <miles.lane@gmail.com>
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"Miles Lane" <miles.lane@gmail.com> wrote:
>
> BUG: unable to handle kernel NULL pointer dereference at virtual
> address 00000020
>  printing eip:
> f8d21f6e
> *pde = 00000000
> Oops: 0000 [#1]
> 4K_STACKS PREEMPT
> last sysfs file: /devices/system/cpu/cpu0/cpufreq/scaling_setspeed
> Modules linked in: sg sd_mod usb_storage libusual pcnet_cs 8390
> aha152x_cs scsi_transport_spi ohci_hcd hostap_cs hostap binfmt_misc
> i915 drm ipv6 speedstep_centrino cpufreq_powersave cpufreq_performance
> cpufreq_conservative video thermal button nls_ascii nls_cp437 vfat fat
> nls_utf8 ntfs nls_base md_mod sr_mod sbp2 scsi_mod parport_pc lp
> parport snd_intel8x0 snd_ac97_codec snd_ac97_bus snd_pcm_oss
> snd_mixer_oss snd_pcm snd_timer ehci_hcd pcspkr evdev iTCO_wdt sdhci
> mmc_core uhci_hcd usbcore psmouse snd ipw2200 rtc intel_agp agpgart
> ohci1394 ieee1394 soundcore snd_page_alloc 8139too
> CPU:    0
> EIP:    0060:[<f8d21f6e>]    Not tainted VLI
> EFLAGS: 00210246   (2.6.17-mm3miles #15)
> EIP is at prism2_registers_proc_read+0x22/0x2ff [hostap_cs]
> eax: 00000000   ebx: f8d21f4c   ecx: 00000000   edx: e884ef64
> esi: d5bd04e4   edi: db8ce000   ebp: e884ef38   esp: e884ef2c
> ds: 007b   es: 007b   ss: 0068
> Process cat (pid: 2219, ti=e884e000 task=cdd3e870 task.ti=e884e000)
> Stack: f8d21f4c 00000400 db8ce000 e884ef78 c1090c8b 00000400 e884ef68 d5bd04e4
>        00000400 0806c000 cac1123c 00000000 00000400 f7b6b838 00000000 00000000
>        dc8ff844 c1090b8c 0806c000 e884ef94 c105fe38 e884efa0 00000400 dc8ff844
> Call Trace:
>  [<c1090c8b>] proc_file_read+0xff/0x218
>  [<c105fe38>] vfs_read+0xa9/0x158
>  [<c1060207>] sys_read+0x3b/0x60
>  [<c1002d6d>] sysenter_past_esp+0x56/0x8d
> Code: c8 8d 65 f4 5b 5e 5f 5d c3 55 89 e5 57 56 53 89 c7 8b 75 10 85
> c9 74 10 8b 45 0c c7 00 01 00 00 00 31 c0 e9 d8 02 00 00 8b 46 14 <8b>
> 50 20 66 ed 0f b7 c0 50 68 03 4a d2 f8 57 e8 42 46 3d c8 8d
> EIP: [<f8d21f6e>] prism2_registers_proc_read+0x22/0x2ff [hostap_cs]
> SS:ESP 0068:e884ef2c

local_info_t.dev is NULL in prism2_registers_proc_read().

Can you please provide a step-by-step means by which others can reproduce
this?