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SubjectOops from tun module
From
I added a tun/tap interface using tunctl(8) from the user-mode-linux
project under 2.6.0-test1, which created a device tap0, owned by user 1000
(tunctl -u 1000). In doing so, the tun module was automatically loaded,
but showed a refcount of 0 in lsmod. I was able to successfully "rmmod
tun", but after doing this every program that tried to open /proc/net/dev
(including ifconfig) immediately segfaults and causes an Oops. I was able
to modprobe tun.o back in and that restored sane behavior. I imagine the
module should have had it's refcount incremented when the device is
created.

Steps to reproduce:

meatloop:/home/daveo# tunctl
Set 'tap0' persistent and owned by uid 0
meatloop:/home/daveo# rmmod tun
meatloop:/home/daveo# ifconfig
Segmentation fault

Oops is as follows:

Unable to handle kernel paging request at virtual address e08b3115
printing eip:
e08b3115
*pde = 01574067
*pte = 00000000
Oops: 0000 [#7]
CPU: 0
EIP: 0060:[<e08b3115>] Not tainted
EFLAGS: 00010282
EIP is at 0xe08b3115
eax: e08b3115 ebx: dfcd5000 ecx: c043ec76 edx: 00000000
esi: deb7e240 edi: dfcd5000 ebp: d8c91f04 esp: d8c91eac
ds: 007b es: 007b ss: 0068
Process ifconfig (pid: 744, threadinfo=d8c90000 task=daa7c180)
Stack: c03767fc dfcd5000 c043ec20 dfcd5c00 00001898 00000040 00000000
00000000
00000000 00000000 00000000 00000000 00001075 00000031 00000000
00000000
00000000 00000000 00000000 00000000 deb7e240 deb7e240 d8c91f24
c0376829
Call Trace:
[<c03767fc>] dev_seq_printf_stats+0xdd/0xe4
[<c0376829>] dev_seq_show+0x26/0x77
[<c01671f4>] seq_read+0x1d0/0x2f7
[<c014a038>] vfs_read+0xc5/0x12f
[<c014a2c4>] sys_read+0x3f/0x5d
[<c01090d3>] syscall_call+0x7/0xb

Code: Bad EIP value.
<6>note: ifconfig[744] exited with preempt_count 1
bad: scheduling while atomic!
Call Trace:
[<c011640c>] schedule+0x3ab/0x3b0
[<c013bc7c>] unmap_page_range+0x41/0x67
[<c013be57>] unmap_vmas+0x1b5/0x20b
[<c013f829>] exit_mmap+0x7a/0x18c
[<c0114b20>] do_page_fault+0x0/0x4cc
[<c0117e18>] mmput+0x67/0xb5
[<c011b9f5>] do_exit+0xf5/0x4ab
[<c0114b20>] do_page_fault+0x0/0x4cc
[<c01098c8>] do_divide_error+0x0/0xdd
[<c0114c4e>] do_page_fault+0x12e/0x4cc
[<c016290d>] get_new_inode_fast+0x41/0xe7
[<c0130867>] find_get_page+0x2c/0x53
[<c0249f8a>] vsnprintf+0x231/0x43b
[<c0114b20>] do_page_fault+0x0/0x4cc
[<c010927d>] error_code+0x2d/0x38
[<c03767fc>] dev_seq_printf_stats+0xdd/0xe4
[<c0376829>] dev_seq_show+0x26/0x77
[<c01671f4>] seq_read+0x1d0/0x2f7
[<c014a038>] vfs_read+0xc5/0x12f
[<c014a2c4>] sys_read+0x3f/0x5d
[<c01090d3>] syscall_call+0x7/0xb



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