linux-kernel - Re: crash while playing bzflag

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Date:	Fri, 07 Sep 2007 19:14:01 -0400
From:	Chuck Ebbert <cebbert@...hat.com>
To:	Alex Riesen <raa.lkml@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: crash while playing bzflag

On 09/07/2007 03:56 PM, Alex Riesen wrote:
> Kernel: v2.6.23-rc5+ (b21010ed6498391c0f359f2a89c907533fe07fec)
> Ubuntu Feisty, Radeon R200 (9200) dual head, MergedFB, BZFlag in
> OpenGL mode, frozen. That'll teach me playing games at home...
> 
> BUG: unable to handle kernel paging request at virtual address ffa85000
>  printing eip:
> c016eed1
> *pde = 00005067
> *pte = 00000000
> Oops: 0000 [#1]
> PREEMPT SMP 
> Modules linked in: binfmt_misc nfs radeon drm nfsd exportfs lockd sunrpc fan firmware_class it87 hwmon_vid hwmon p4_clockmod speedstep_lib ipv6 sg sr_mod cdrom usb_storage snd_intel8x0 snd_ac97_codec ac97_bus snd_pcm_oss snd_pcm snd_mixer_oss snd_seq_oss snd_seq_midi snd_rawmidi snd_seq_midi_event snd_seq snd_timer snd_seq_device generic floppy snd ide_core intel_agp e100 uhci_hcd ehci_hcd soundcore snd_page_alloc agpgart evdev
> CPU:    0
> EIP:    0060:[__link_path_walk+2146/2867]    Not tainted VLI
> EFLAGS: 00010287   (2.6.23-rc5-t #138)
> EIP is at __link_path_walk+0x862/0xb33
> eax: ffa85000   ebx: f0a4dd64   ecx: c0442130   edx: c1782d00
> esi: eee51f30   edi: ffa85000   ebp: f0e49e40   esp: eee51de4
> ds: 007b   es: 007b   fs: 00d8  gs: 0033  ss: 0068
> Process command-not-fou (pid: 2895, ti=eee51000 task=f08f1020 task.ti=eee51000)
> Stack: f474c02c 00000101 f1db2d64 c016d3eb c1782d00 ffa85000 00000000 00000000 
>        00000000 96ba5598 0000000b f474c021 c18eff00 f0e49e40 f08e1540 eee51f30 
>        c1937c78 c18eff00 c016f1e6 f474c000 c1937c78 c18eff00 c180b180 f11a7600 
> Call Trace:
>  [do_lookup+79/323] do_lookup+0x4f/0x143
>  [link_path_walk+68/179] link_path_walk+0x44/0xb3
>  [_spin_unlock+5/28] _spin_unlock+0x5/0x1c
>  [get_unused_fd_flags+198/208] get_unused_fd_flags+0xc6/0xd0
>  [do_path_lookup+362/463] do_path_lookup+0x16a/0x1cf
>  [__path_lookup_intent_open+69/117] __path_lookup_intent_open+0x45/0x75
>  [path_lookup_open+32/37] path_lookup_open+0x20/0x25
>  [open_namei+114/1364] open_namei+0x72/0x554
>  [unmap_vmas+791/1240] unmap_vmas+0x317/0x4d8
>  [do_filp_open+37/57] do_filp_open+0x25/0x39
>  [_spin_unlock+5/28] _spin_unlock+0x5/0x1c
>  [get_unused_fd_flags+198/208] get_unused_fd_flags+0xc6/0xd0
>  [do_sys_open+68/192] do_sys_open+0x44/0xc0
>  [sys_open+28/30] sys_open+0x1c/0x1e
>  [sysenter_past_esp+95/133] sysenter_past_esp+0x5f/0x85
>  [xfrm_bundle_ok+53/522] xfrm_bundle_ok+0x35/0x20a
>  =======================
> Code: f0 ff ff 0f 87 38 01 00 00 8b 46 1c 8b 44 86 20 89 44 24 14 31 ff 85 c0 0f 84 09 01 00 00 89 c7 3d 00 f0 ff ff 0f 87 f5 00 00 00 <80> 38 2f 0f 85 9f 00 00 00 89 f0 e8 38 e1 ff ff 64 a1 00 70 3f 
> EIP: [__link_path_walk+2146/2867] __link_path_walk+0x862/0xb33 SS:ESP 0068:eee51de4
> SysRq : Emergency Sync
> Emergency Sync complete
> SysRq : Emergency Sync
> Emergency Sync complete
> 
> The config, lspci output, Xorg.0.log, and a more complete log of the
> crash attached (the crash happened around Sep  7 21:24:27 in the log,
> I panicked a bit and pressed Alt-SysRq-t and emergency sync).

Whee...

here, in __vfs_follow_link:

        if (*link == '/') {   <================ link points to unmapped memory
                path_release(nd);
                if (!walk_init_root(link, nd))
                        /* weird __emul_prefix() stuff did it */
                        goto out;
        }

inlined from __do_follow_link:

        if (!IS_ERR(cookie)) {
                char *s = nd_get_link(nd);
                error = 0;
                if (s)
                        error = __vfs_follow_link(nd, s);
                if (dentry->d_inode->i_op->put_link)
                        dentry->d_inode->i_op->put_link(dentry, nd, cookie);
        }

__do_follow_link is inlined from do_follow_link

presumably inlined here:

                if ((lookup_flags & LOOKUP_FOLLOW)
                    && inode && inode->i_op && inode->i_op->follow_link) {
                        err = do_follow_link(&next, nd);
                        if (err)
                                goto return_err;
                        inode = nd->dentry->d_inode;
                } else

What filesystem was this?
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