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nfsd4: fix unlikely race in session replay case 

In the replay case, the

	renew_client(session->se_client);

happens after we've droppped the sessionid_lock, and without holding a
reference on the session; so there's nothing preventing the session
being freed before we get here.

Thanks to Benny Halevy for catching a bug in an earlier version of this
patch.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Acked-by: Benny Halevy <bhalevy@panasas.com>
This commit is contained in:
J. Bruce Fields 2010-04-24 15:35:43 -04:00
parent e0c8233622
commit 26c0c75e69
3 changed files with 10 additions and 8 deletions
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1
fs/nfsd/nfs4proc.c
View File

@ -1027,6 +1027,7 @@ nfsd4_proc_compound(struct svc_rqst *rqstp,
resp->rqstp = rqstp;
resp->cstate.minorversion = args->minorversion;
resp->cstate.replay_owner = NULL;
resp->cstate.session = NULL;
fh_init(&resp->cstate.current_fh, NFS4_FHSIZE);
fh_init(&resp->cstate.save_fh, NFS4_FHSIZE);
/* Use the deferral mechanism only for NFSv4.0 compounds */

7
fs/nfsd/nfs4state.c
View File

@ -1443,11 +1443,10 @@ nfsd4_sequence(struct svc_rqst *rqstp,
cstate->slot = slot;
cstate->session = session;
/* Hold a session reference until done processing the compound:
* nfsd4_put_session called only if the cstate slot is set.
*/
nfsd4_get_session(session);
out:
/* Hold a session reference until done processing the compound. */
if (cstate->session)
nfsd4_get_session(cstate->session);
spin_unlock(&sessionid_lock);
/* Renew the clientid on success and on replay */
if (cstate->session) {

10
fs/nfsd/nfs4xdr.c
View File

@ -3306,10 +3306,12 @@ nfs4svc_encode_compoundres(struct svc_rqst *rqstp, __be32 *p, struct nfsd4_compo
iov = &rqstp->rq_res.head[0];
iov->iov_len = ((char*)resp->p) - (char*)iov->iov_base;
BUG_ON(iov->iov_len > PAGE_SIZE);
if (nfsd4_has_session(cs) && cs->status != nfserr_replay_cache) {
nfsd4_store_cache_entry(resp);
dprintk("%s: SET SLOT STATE TO AVAILABLE\n", __func__);
resp->cstate.slot->sl_inuse = false;
if (nfsd4_has_session(cs)) {
if (cs->status != nfserr_replay_cache) {
nfsd4_store_cache_entry(resp);
dprintk("%s: SET SLOT STATE TO AVAILABLE\n", __func__);
resp->cstate.slot->sl_inuse = false;
}
nfsd4_put_session(resp->cstate.session);
}
return 1;