Re: [PATCH] SUNRPC: Set alloc_slot for backchannel tcp ops

[Bryan Schumaker <bjschuma@netapp.com>]

On 09/24/2012 01:42 PM, J. Bruce Fields wrote:
> On Mon, Sep 24, 2012 at 01:39:01PM -0400, bjschuma@netapp.com wrote:
>> From: Bryan Schumaker <bjschuma@netapp.com>
>>
>> f39c1bfb5a03e2d255451bff05be0d7255298fa4 (SUNRPC: Fix a UDP transport
>> regression) introduced the "alloc_slot" function for xprt operations,
>> but never created one for the backchannel operations.  This patch fixes
>> a null pointer dereference when mounting NFS over v4.1.
> 
> Thanks, I just rebased some of my work to 3.6 and ran across that!  It
> crashes the 4.1 server very quickly....

That sounds like my story.  It got my peer-to-peer server right away, too.

- Bryan

> 
> --b.
> 
>>
>> Call Trace:
>>  [<ffffffffa0207957>] ? xprt_reserve+0x47/0x50 [sunrpc]
>>  [<ffffffffa02023a4>] call_reserve+0x34/0x60 [sunrpc]
>>  [<ffffffffa020e280>] __rpc_execute+0x90/0x400 [sunrpc]
>>  [<ffffffffa020e61a>] rpc_async_schedule+0x2a/0x40 [sunrpc]
>>  [<ffffffff81073589>] process_one_work+0x139/0x500
>>  [<ffffffff81070e70>] ? alloc_worker+0x70/0x70
>>  [<ffffffffa020e5f0>] ? __rpc_execute+0x400/0x400 [sunrpc]
>>  [<ffffffff81073d1e>] worker_thread+0x15e/0x460
>>  [<ffffffff8145c839>] ? preempt_schedule+0x49/0x70
>>  [<ffffffff81073bc0>] ? rescuer_thread+0x230/0x230
>>  [<ffffffff81079603>] kthread+0x93/0xa0
>>  [<ffffffff81465d04>] kernel_thread_helper+0x4/0x10
>>  [<ffffffff81079570>] ? kthread_freezable_should_stop+0x70/0x70
>>  [<ffffffff81465d00>] ? gs_change+0x13/0x13
>>
>> Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
>> ---
>>  net/sunrpc/xprtsock.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
>> index 86b7777..aaaadfb 100644
>> --- a/net/sunrpc/xprtsock.c
>> +++ b/net/sunrpc/xprtsock.c
>> @@ -2521,6 +2521,7 @@ static struct rpc_xprt_ops xs_tcp_ops = {
>>  static struct rpc_xprt_ops bc_tcp_ops = {
>>  	.reserve_xprt		= xprt_reserve_xprt,
>>  	.release_xprt		= xprt_release_xprt,
>> +	.alloc_slot		= xprt_alloc_slot,
>>  	.rpcbind		= xs_local_rpcbind,
>>  	.buf_alloc		= bc_malloc,
>>  	.buf_free		= bc_free,
>> -- 
>> 1.7.12.1
>>
>> --
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