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

["J. Bruce Fields" <bfields@fieldses.org>]

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....

--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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