Re: [ 18/71] SUNRPC: Ensure we release the socket write lock if therpc_task exits early

[Greg Kroah-Hartman]

On Thu, Jan 17, 2013 at 01:14:59PM -0200, Herton Ronaldo Krzesinski wrote:
> On Tue, Jan 15, 2013 at 02:54:15PM -0800, Greg Kroah-Hartman wrote:
> > 3.0-stable review patch.  If anyone has any objections, please let me know.
> > 
> > ------------------
> > 
> > From: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
> > 
> > commit 87ed50036b866db2ec2ba16b2a7aec4a2b0b7c39 upstream.
> > 
> > If the rpc_task exits while holding the socket write lock before it has
> > allocated an rpc slot, then the usual mechanism for releasing the write
> > lock in xprt_release() is defeated.
> > 
> > The problem occurs if the call to xprt_lock_write() initially fails, so
> > that the rpc_task is put on the xprt->sending wait queue. If the task
> > exits after being assigned the lock by __xprt_lock_write_func, but
> > before it has retried the call to xprt_lock_and_alloc_slot(), then
> > it calls xprt_release() while holding the write lock, but will
> > immediately exit due to the test for task->tk_rqstp != NULL.
> > 
> > Reported-by: Chris Perl <chris.perl@xxxxxxxxx>
> > Signed-off-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> 
> This is marked only for kernel versions 3.1 and later, which looks
> correct as it seems to address a problem starting with commit
> 43cedbf0e8dfb9c5610eb7985d5f21263e313802

Ah, good catch, I've now dropped it from the 3.0-stable queue, thanks.

greg k-h
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