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krpc: Acquire ref count of CLIENT for backchannel use

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Michael Dexter <editor@callfortesting.org> reported
a crash in FreeNAS, where the first argument to
clnt_bck_svccall() was no longer valid.
This argument is a pointer to the callback CLIENT
structure, which is free'd when the associated
NFSv4 ClientID is free'd.

This appears to have occurred because a callback
reply was still in the socket receive queue when
the CLIENT structure was free'd.

This patch acquires a reference count on the CLIENT
that is not CLNT_RELEASE()'d until the socket structure
is destroyed. This should guarantee that the CLIENT
structure is still valid when clnt_bck_svccall() is called.
It also adds a check for closed or closing to
clnt_bck_svccall() so that it will not process the callback
RPC reply message after the ClientID is free'd.

Comments by:	mav
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D30153
This commit is contained in:
Rick Macklem 2021-06-11 16:57:14 -07:00
parent 30b915d7b2
commit e1a907a25c
4 changed files with 25 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
sys/fs/nfsserver/nfs_nfsdstate.c
View File

@ -721,8 +721,8 @@ nfsrv_getclient(nfsquad_t clientid, int opflags, struct nfsclient **clpp,
cbprogram, NFSV4_CBVERS);
if (clp->lc_req.nr_client != NULL) {
SVC_ACQUIRE(nd->nd_xprt);
nd->nd_xprt->xp_p2 =
clp->lc_req.nr_client->cl_private;
CLNT_ACQUIRE(clp->lc_req.nr_client);
nd->nd_xprt->xp_p2 = clp->lc_req.nr_client;
/* Disable idle timeout. */
nd->nd_xprt->xp_idletimeout = 0;
nsep->sess_cbsess.nfsess_xprt = nd->nd_xprt;
@ -6464,8 +6464,8 @@ nfsrv_bindconnsess(struct nfsrv_descript *nd, uint8_t *sessionid, int *foreaftp)
"backchannel\n");
savxprt = sep->sess_cbsess.nfsess_xprt;
SVC_ACQUIRE(nd->nd_xprt);
nd->nd_xprt->xp_p2 =
clp->lc_req.nr_client->cl_private;
CLNT_ACQUIRE(clp->lc_req.nr_client);
nd->nd_xprt->xp_p2 = clp->lc_req.nr_client;
/* Disable idle timeout. */
nd->nd_xprt->xp_idletimeout = 0;
sep->sess_cbsess.nfsess_xprt = nd->nd_xprt;

13
sys/rpc/clnt_bck.c
View File

@ -566,15 +566,26 @@ clnt_bck_destroy(CLIENT *cl)
/*
* This call is done by the svc code when a backchannel RPC reply is
* received.
* For the server end, where callback RPCs to the client are performed,
* xp_p2 points to the "CLIENT" and not the associated "struct ct_data"
* so that svc_vc_destroy() can CLNT_RELEASE() the reference count on it.
*/
void
clnt_bck_svccall(void *arg, struct mbuf *mrep, uint32_t xid)
{
struct ct_data *ct = (struct ct_data *)arg;
CLIENT *cl = (CLIENT *)arg;
struct ct_data *ct;
struct ct_request *cr;
int foundreq;
ct = (struct ct_data *)cl->cl_private;
mtx_lock(&ct->ct_lock);
if (ct->ct_closing || ct->ct_closed) {
mtx_unlock(&ct->ct_lock);
m_freem(mrep);
return;
}
ct->ct_upcallrefs++;
/*
* See if we can match this reply to a request.

5
sys/rpc/svc.h
View File

@ -148,6 +148,11 @@ struct __rpc_svcthread;
* reference count which tracks the number of currently assigned
* worker threads plus one for the service pool's reference.
* For NFSv4.1 sessions, a reference is also held for a backchannel.
* xp_p2 - Points to the CLIENT structure for the RPC server end
* (the client end for callbacks).
* Points to the private structure (cl_private) for the
* CLIENT structure for the RPC client end (the server
* end for callbacks).
*/
typedef struct __rpc_svcxprt {
#ifdef _KERNEL

4
sys/rpc/svc_vc.c
View File

@ -500,6 +500,7 @@ static void
svc_vc_destroy(SVCXPRT *xprt)
{
struct cf_conn *cd = (struct cf_conn *)xprt->xp_p1;
CLIENT *cl = (CLIENT *)xprt->xp_p2;
SOCKBUF_LOCK(&xprt->xp_socket->so_rcv);
if (xprt->xp_upcallset) {
@ -509,6 +510,9 @@ svc_vc_destroy(SVCXPRT *xprt)
}
SOCKBUF_UNLOCK(&xprt->xp_socket->so_rcv);
if (cl != NULL)
CLNT_RELEASE(cl);
svc_vc_destroy_common(xprt);
if (cd->mreq)