Re: [PATCH] NFSv4: nfs4_state_manager() vs. nfs_server_remove_lists()

[Steve Dickson <SteveD@redhat.com>]

On 09/17/2014 10:55 AM, Trond Myklebust wrote:
> On Wed, Sep 17, 2014 at 10:50 AM, Steve Dickson <steved@redhat.com> wrote:
>> There is a race between nfs4_state_manager() and
>> nfs_server_remove_lists() that happens during a nfsv3 mount.
>>
>> The v3 mount notices there is already a supper block so
>> nfs_server_remove_lists() called which uses the nfs_client_lock
>> spin lock to synchronize access to the client list.
>>
>> At the same time nfs4_state_manager() is running through
>> the client list looking for work to do, using the same
>> lock. When nfs4_state_manager() wins the race to the
>> list, a v3 client pointer is found and not ignored
>> properly which causes the panic.
>>
>> Moving some protocol checks before the state checking
>> avoids the panic.
>>
>> CC: Stable Tree <stable@vger.kernel.org>
>> Signed-off-by: Steve Dickson <steved@redhat.com>
>> ---
>>  fs/nfs/nfs4client.c | 19 ++++++++++---------
>>  1 file changed, 10 insertions(+), 9 deletions(-)
>>
>> diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
>> index 53e435a..7ff4c02 100644
>> --- a/fs/nfs/nfs4client.c
>> +++ b/fs/nfs/nfs4client.c
>> @@ -622,6 +622,16 @@ int nfs41_walk_client_list(struct nfs_client *new,
>>
>>         spin_lock(&nn->nfs_client_lock);
>>         list_for_each_entry(pos, &nn->nfs_client_list, cl_share_link) {
>> +
>> +               if (pos->rpc_ops != new->rpc_ops)
>> +                       continue;
>> +
>> +               if (pos->cl_proto != new->cl_proto)
>> +                       continue;
>> +
>> +               if (pos->cl_minorversion != new->cl_minorversion)
>> +                       continue;
>> +
>>                 /* If "pos" isn't marked ready, we can't trust the
>>                  * remaining fields in "pos", especially the client
>>                  * ID and serverowner fields.  Wait for CREATE_SESSION
>> @@ -647,15 +657,6 @@ int nfs41_walk_client_list(struct nfs_client *new,
>>                 if (pos->cl_cons_state != NFS_CS_READY)
>>                         continue;
>>
>> -               if (pos->rpc_ops != new->rpc_ops)
>> -                       continue;
>> -
>> -               if (pos->cl_proto != new->cl_proto)
>> -                       continue;
>> -
>> -               if (pos->cl_minorversion != new->cl_minorversion)
>> -                       continue;
>> -
>>                 if (!nfs4_match_clientids(pos, new))
>>                         continue;
>>
>> --
>> 1.8.3.1
>>
> 
> Don't we need the same fix in nfs40_walk_client_list?
Yes... Just posted version 2...

steved.
 
> 
> Cheers
>   Trond
>