Re: [PATCH] [RFC] nfsd: fix possible dereference of static NULL nfsd_serv pointer

[Stanislav Kinsbursky <skinsbursky@parallels.com>]

06.07.2012 21:26, J. Bruce Fields пишет:
> On Fri, Jul 06, 2012 at 05:45:56PM +0400, Stanislav Kinsbursky wrote:
>> This is a bug fix for 3.5 kernel.
>> In case on NFSd service start failure svc_shutdown_net() will call svc_destroy
>> callback and zeroize global nfsd_serv pointer, this in turn will lead to Oops
>> in svc_destroy().
>>
>> This patch is marked as RFC, because to many lines were changed. It can be
>> easely simplified if requested.
>> Moreover, NFSd service shutdown is going to be converted into csomething on
>> per-net basis.
> Doesn't this leave error paths in e.g. __write_ports_addfd() and
> __write_ports_addxprt() unfixed?

Yes, sure it does...

> I'm inclined to just submit your original fix (split up as in the last
> version I sent) for 3.5 if you don't object.

Not at all.
Thanks, Bruce.

> --b.
>
>> Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
>> ---
>>   fs/nfsd/nfssvc.c |   14 ++++++++------
>>   1 files changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
>> index ee709fc..526a4aa 100644
>> --- a/fs/nfsd/nfssvc.c
>> +++ b/fs/nfsd/nfssvc.c
>> @@ -446,6 +446,7 @@ nfsd_svc(unsigned short port, int nrservs)
>>   	int	error;
>>   	bool	nfsd_up_before;
>>   	struct net *net = &init_net;
>> +	struct svc_serv *serv = nfsd_serv;
>>   
>>   	mutex_lock(&nfsd_mutex);
>>   	dprintk("nfsd: creating service\n");
>> @@ -454,7 +455,7 @@ nfsd_svc(unsigned short port, int nrservs)
>>   	if (nrservs > NFSD_MAXSERVS)
>>   		nrservs = NFSD_MAXSERVS;
>>   	error = 0;
>> -	if (nrservs == 0 && nfsd_serv == NULL)
>> +	if (nrservs == 0 && serv == NULL)
>>   		goto out;
>>   
>>   	error = nfsd_create_serv();
>> @@ -464,23 +465,24 @@ nfsd_svc(unsigned short port, int nrservs)
>>   	nfsd_up_before = nfsd_up;
>>   
>>   	error = nfsd_startup(port, nrservs);
>> +	error = -EINVAL;
>>   	if (error)
>>   		goto out_destroy;
>> -	error = svc_set_num_threads(nfsd_serv, NULL, nrservs);
>> +	error = svc_set_num_threads(serv, NULL, nrservs);
>>   	if (error)
>>   		goto out_shutdown;
>>   	/* We are holding a reference to nfsd_serv which
>>   	 * we don't want to count in the return value,
>>   	 * so subtract 1
>>   	 */
>> -	error = nfsd_serv->sv_nrthreads - 1;
>> +	error = serv->sv_nrthreads - 1;
>>   out_shutdown:
>>   	if (error < 0 && !nfsd_up_before)
>>   		nfsd_shutdown();
>>   out_destroy:
>> -	if (nfsd_serv->sv_nrthreads == 1)
>> -		svc_shutdown_net(nfsd_serv, net);
>> -	svc_destroy(nfsd_serv);		/* Release server */
>> +	if (serv->sv_nrthreads == 1)
>> +		svc_shutdown_net(serv, net);
>> +	svc_destroy(serv);		/* Release server */
>>   out:
>>   	mutex_unlock(&nfsd_mutex);
>>   	return error;
>>