Messages in this thread | | | Date | Tue, 28 Jul 2009 16:05:27 -0700 | From | Andrew Morton <> | Subject | Re: [Bugme-new] [Bug 13850] New: reading /proc/kcore causes oops |
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(switched to email. Please respond via emailed reply-to-all, not via the bugzilla web interface).
On Mon, 27 Jul 2009 03:19:11 GMT bugzilla-daemon@bugzilla.kernel.org wrote:
> http://bugzilla.kernel.org/show_bug.cgi?id=13850 > > Summary: reading /proc/kcore causes oops > Product: Other > Version: 2.5 > Kernel Version: 2.6.30 > Platform: All > OS/Version: Linux > Tree: Mainline > Status: NEW > Severity: normal > Priority: P1 > Component: Other > AssignedTo: other_other@kernel-bugs.osdl.org > ReportedBy: scgtrp@gmail.com > Regression: No > > > When trying to use an old trick for finding lost data by grep'ing /proc/kcore, > I managed to oops my server's kernel. I tried again on my desktop with cat > /proc/kcore >/dev/null. cat was killed, and a similar oops appeared in my dmesg > which I managed to capture: > > Jul 26 23:04:13 mike kernel: BUG: unable to handle kernel paging request at > e07cf000 > Jul 26 23:04:13 mike kernel: IP: [<c0224dd1>] read_kcore+0x2c1/0x4b0 > Jul 26 23:04:13 mike kernel: *pde = 1b5f4067 *pte = 00000000 > Jul 26 23:04:13 mike kernel: Oops: 0000 [#2] PREEMPT SMP > Jul 26 23:04:13 mike kernel: last sysfs file: /sys/power/state > Jul 26 23:04:13 mike kernel: Modules linked in: ipv6 sg sd_mod fuse usb_storage > usbhid hid snd_seq_dummy snd_seq_oss snd_seq_midi_event snd_seq snd_seq_device > snd_pcm_oss snd_mixer_oss ppdev snd_intel8x0 snd_ac97_codec ac97_bus snd_pcm > snd_timer ohci_hcd parport_pc lp parport snd soundcore snd_page_alloc nvidia(P) > agpgart k8temp ehci_hcd forcedeth i2c_nforce2 i2c_core usbcore evdev thermal > processor fan button battery ac rtc_cmos rtc_core rtc_lib ext3 jbd mbcache > ide_gd_mod ide_cd_mod cdrom sata_nv libata amd74xx ide_pci_generic ide_core > scsi_mod > Jul 26 23:04:13 mike kernel: > Jul 26 23:04:13 mike kernel: Pid: 4835, comm: cat Tainted: P D > (2.6.30-ARCH #1) W3107 > Jul 26 23:04:13 mike kernel: EIP: 0060:[<c0224dd1>] EFLAGS: 00210286 CPU: 0 > Jul 26 23:04:13 mike kernel: EIP is at read_kcore+0x2c1/0x4b0 > Jul 26 23:04:13 mike kernel: EAX: ddb71ac0 EBX: 00001000 ECX: 00000400 EDX: > e07d0000 > Jul 26 23:04:13 mike kernel: ESI: e07cf000 EDI: da20e000 EBP: d73fbf30 ESP: > d73fbefc > Jul 26 23:04:13 mike kernel: DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 > Jul 26 23:04:13 mike kernel: Process cat (pid: 4835, ti=d73fa000 task=d4b5cc00 > task.ti=d73fa000) > Jul 26 23:04:13 mike kernel: Stack: > Jul 26 23:04:13 mike kernel: da20e000 e07cf000 d73fbf90 00000000 09459000 > 00000000 00008000 00001000 > Jul 26 23:04:13 mike kernel: 00000000 6798ed89 ddaf0000 ce920c80 c0224b10 > fffffffb c0219e89 d73fbf90 > Jul 26 23:04:13 mike kernel: 09459000 00008000 d73fbf90 6798ed89 ce920c80 > 00008000 09459000 d73fbf80 > Jul 26 23:04:13 mike kernel: Call Trace: > Jul 26 23:04:13 mike kernel: [<c0224b10>] ? read_kcore+0x0/0x4b0 > Jul 26 23:04:13 mike kernel: [<c0219e89>] ? proc_reg_read+0x79/0xc0 > Jul 26 23:04:13 mike kernel: [<c01d1b43>] ? vfs_read+0xc3/0x1a0 > Jul 26 23:04:13 mike kernel: [<c0219e10>] ? proc_reg_read+0x0/0xc0 > Jul 26 23:04:13 mike kernel: [<c01d1d28>] ? sys_read+0x58/0xb0 > Jul 26 23:04:13 mike kernel: [<c0103c73>] ? sysenter_do_call+0x12/0x28 > Jul 26 23:04:13 mike kernel: Code: 89 fb 0f 43 f2 89 ca 29 f2 29 f3 39 f9 0f 46 > da 29 5c 24 14 f6 40 0c 01 8d 14 33 75 19 89 d9 89 f7 c1 e9 02 2b 7c 24 04 03 > 3c 24 <f3> a5 89 d9 83 e1 03 74 02 f3 a4 8b 4c 24 14 8b 00 85 c9 74 0a > Jul 26 23:04:13 mike kernel: EIP: [<c0224dd1>] read_kcore+0x2c1/0x4b0 SS:ESP > 0068:d73fbefc > Jul 26 23:04:13 mike kernel: CR2: 00000000e07cf000 > Jul 26 23:04:13 mike kernel: ---[ end trace 3bb140bf57c1987e ]--- > Jul 26 23:04:13 mike kernel: note: cat[4835] exited with preempt_count 1 > > I understand it's quite a ridiculous thing to do, but userspace shouldn't be > able to cause kernel errors, no matter what kind of insane things I try. >
gee, read_kcore() is huge. This makes it pretty hard to work out where exactly the kernel died.
Is it reproducible, or do you still have the vmlinux from the above oops on-disk?
If so, can you please help work out where it crashed? You could run something like
addr2line -e vmlinux 0xc0224dd1
or
gdb vmlinux (gdb) l *0xc0224dd1
both of these will need CONFIG_DEBUG_INFO=y.
It is possible to work out where the kernel crashed using the above Code: line, but it's a bit of a pain.
Thanks.
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