[Devel] [patch 0/1] fix veth netif_carrier_off

[dlezcano at fr.ibm.com]

When I tryed the veth driver, I fall into a kernel oops.

qemu login: Oops: 0000 [#1]
Modules linked in:
CPU:    0
EIP:    0060:[<c0265c9e>]    Not tainted VLI
EFLAGS: 00000202   (2.6.23-rc6-g754f885d-dirty #33)
EIP is at __linkwatch_run_queue+0x6a/0x175
eax: c7fc9550   ebx: 6b6b6b6b   ecx: c3360c80   edx: 00000246
esi: 00000001   edi: 6b6b6b6b   ebp: c7fd9f7c   esp: c7fd9f5c
ds: 007b   es: 007b   fs: 0000  gs: 0000  ss: 0068
Process events/0 (pid: 5, ti=c7fd8000 task=c7fc9550 task.ti=c7fd8000)
Stack: c7fee5a8 c0387680 c7fd9f74 c02e1aaa 4f732564 c0387684 c7fee5a8 c0387680 
       c7fd9f84 c0265dc9 c7fd9fac c011fb3c c7fd9f94 c02e277e c7fd9fac c02e1166 
       c0265da9 c7fee5a8 c0120203 c7fd9fc8 c7fd9fd0 c01202ba 00000000 c7fc9550 
Call Trace:
 [<c0102c69>] show_trace_log_lvl+0x1a/0x2f
 [<c0102d1b>] show_stack_log_lvl+0x9d/0xa5
 [<c0102ee1>] show_registers+0x1be/0x28f
 [<c010309a>] die+0xe8/0x208
 [<c010d5a1>] do_page_fault+0x4ba/0x595
 [<c02e2842>] error_code+0x6a/0x70
 [<c0265dc9>] linkwatch_event+0x20/0x27
 [<c011fb3c>] run_workqueue+0x7c/0x102
 [<c01202ba>] worker_thread+0xb7/0xc5
 [<c012270c>] kthread+0x39/0x61
 [<c0102913>] kernel_thread_helper+0x7/0x10
 =======================
Code: b8 60 76 38 c0 e8 e3 ca 07 00 b8 60 76 38 c0 8b 1d 78 a7 3d c0 c7 05 78 a7 3d c0 00 00 00 00 e8 df ca 07 00 e9 ed 00 00 00 85 f6 <8b> bb f4 01 00 00 74 17 89 d8 e8 73 fe ff ff 85 c0 75 0c 89 d8 
EIP: [<c0265c9e>] __linkwatch_run_queue+0x6a/0x175 SS:ESP 0068:c7fd9f5c
Slab corruption: size-2048 start=c473eac8, len=2048
Redzone: 0x9f911029d74e35b/0x9f911029d74e35b.
Last user: [<c025be72>](free_netdev+0x1f/0x41)
200: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b c0 e2 73 c4
Prev obj: start=c473e2b0, len=2048
Redzone: 0xd84156c5635688c0/0xd84156c5635688c0.
Last user: [<c025bed0>](alloc_netdev_mq+0x3c/0xa1)
000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
010: 76 65 74 68 30 00 00 00 00 00 00 00 00 00 00 00
Next obj: start=c473f2e0, len=2048
Redzone: 0x9f911029d74e35b/0x9f911029d74e35b.
Last user: [<c0260e69>](neigh_sysctl_unregister+0x2b/0x2e)
000: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
010: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b

That happens when trying to add the veth driver using the ip command:

	ip link add veth0 

which fail.

It appears that the netif_carrier_off is placed into the setup function
and this one is called before register_netdevice.

The register_netdevice function does a lot of initialization to the netdev
and if the netif_carrier_off is called before the register_netdev function,
it will use and trigger an event for an uninitialized netdev.

-- 
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