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    SubjectRe: [PATCH 2/3] SUNRPC: check rpcbind clients usage counter before decrement
    On Fri, Apr 27, 2012 at 06:08:13PM +0400, Stanislav Kinsbursky wrote:
    > On 27.04.2012 17:55, J. Bruce Fields wrote:
    > >On Wed, Apr 25, 2012 at 05:37:49PM +0400, Stanislav Kinsbursky wrote:
    > >>Registering service with svc_bind() can fail. In this case service will be
    > >>destroyed and during destruction it will try to unregister itself from rpcbind.
    > >>In this case unregister have to be skipped.
    > >
    > >Isn't this a preexisting bug, in which case perhaps Trond should at it
    > >to his list of bugs to submit now?
    > >
    >
    > Not it's not.
    >
    > Previously, in case of bind operations failure, rpcb_put_local()
    > wasn't called, but service data was destroyed instead:
    >
    > - if (svc_uses_rpcbind(serv)) {
    > - if (svc_rpcb_setup(serv, current->nsproxy->net_ns) < 0) {
    > - kfree(serv->sv_pools);
    > - kfree(serv);
    > - return NULL;
    > - }
    > - if (!serv->sv_shutdown)
    > - serv->sv_shutdown = svc_rpcb_cleanup;
    > - }
    >
    > Now (with svc_bind() introduction) service can be created, but
    > svc_bind() could fail. And thus svc_destroy() have to be called.
    > Which will call rpcb_put_local().
    >
    > And the problem here that svc_bind() can fail before incrementing of
    > rpcb usage counter.

    OK, but then you're fixing a bug that you just introduced with the
    previous patch.

    So this should be combined with the previous patch.

    --b.

    >
    > >--b.
    > >
    > >>
    > >>Signed-off-by: Stanislav Kinsbursky<skinsbursky@parallels.com>
    > >>
    > >>---
    > >> net/sunrpc/rpcb_clnt.c | 12 +++++++-----
    > >> 1 files changed, 7 insertions(+), 5 deletions(-)
    > >>
    > >>diff --git a/net/sunrpc/rpcb_clnt.c b/net/sunrpc/rpcb_clnt.c
    > >>index 78ac39f..4c38b33 100644
    > >>--- a/net/sunrpc/rpcb_clnt.c
    > >>+++ b/net/sunrpc/rpcb_clnt.c
    > >>@@ -180,14 +180,16 @@ void rpcb_put_local(struct net *net)
    > >> struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
    > >> struct rpc_clnt *clnt = sn->rpcb_local_clnt;
    > >> struct rpc_clnt *clnt4 = sn->rpcb_local_clnt4;
    > >>- int shutdown;
    > >>+ int shutdown = 0;
    > >>
    > >> spin_lock(&sn->rpcb_clnt_lock);
    > >>- if (--sn->rpcb_users == 0) {
    > >>- sn->rpcb_local_clnt = NULL;
    > >>- sn->rpcb_local_clnt4 = NULL;
    > >>+ if (sn->rpcb_users) {
    > >>+ if (--sn->rpcb_users == 0) {
    > >>+ sn->rpcb_local_clnt = NULL;
    > >>+ sn->rpcb_local_clnt4 = NULL;
    > >>+ }
    > >>+ shutdown = !sn->rpcb_users;
    > >> }
    > >>- shutdown = !sn->rpcb_users;
    > >> spin_unlock(&sn->rpcb_clnt_lock);
    > >>
    > >> if (shutdown) {
    > >>
    >
    >
    > --
    > Best regards,
    > Stanislav Kinsbursky


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