[PATCH 4.4 031/146] nfsd: Always lock state exclusively.

Greg Kroah-Hartman
2016-07-25T21:04:15Z

From: Oleg Drokin <green@linuxhacker.ru>

commit feb9dad5209280085d5b0c094fa67e7a8d75c81a upstream.

It used to be the case that state had an rwlock that was locked for write
by downgrades, but for read for upgrades (opens). Well, the problem is
if there are two competing opens for the same state, they step on
each other toes potentially leading to leaking file descriptors
from the state structure, since access mode is a bitmap only set once.

Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/nfsd/nfs4state.c | 40 ++++++++++++++++++++--------------------
fs/nfsd/state.h | 2 +-
2 files changed, 21 insertions(+), 21 deletions(-)

--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -3467,7 +3467,7 @@ init_open_stateid(struct nfs4_ol_stateid
stp->st_access_bmap = 0;
stp->st_deny_bmap = 0;
stp->st_openstp = NULL;
- init_rwsem(&stp->st_rwsem);
+ mutex_init(&stp->st_mutex);
list_add(&stp->st_perstateowner, &oo->oo_owner.so_stateids);
list_add(&stp->st_perfile, &fp->fi_stateids);

@@ -4300,10 +4300,10 @@ nfsd4_process_open2(struct svc_rqst *rqs
*/
if (stp) {
/* Stateid was found, this is an OPEN upgrade */
- down_read(&stp->st_rwsem);
+ mutex_lock(&stp->st_mutex);
status = nfs4_upgrade_open(rqstp, fp, current_fh, stp, open);
if (status) {
- up_read(&stp->st_rwsem);
+ mutex_unlock(&stp->st_mutex);
goto out;
}
} else {
@@ -4313,19 +4313,19 @@ nfsd4_process_open2(struct svc_rqst *rqs
if (swapstp) {
nfs4_put_stid(&stp->st_stid);
stp = swapstp;
- down_read(&stp->st_rwsem);
+ mutex_lock(&stp->st_mutex);
status = nfs4_upgrade_open(rqstp, fp, current_fh,
stp, open);
if (status) {
- up_read(&stp->st_rwsem);
+ mutex_unlock(&stp->st_mutex);
goto out;
}
goto upgrade_out;
}
- down_read(&stp->st_rwsem);
+ mutex_lock(&stp->st_mutex);
status = nfs4_get_vfs_file(rqstp, fp, current_fh, stp, open);
if (status) {
- up_read(&stp->st_rwsem);
+ mutex_unlock(&stp->st_mutex);
release_open_stateid(stp);
goto out;
}
@@ -4337,7 +4337,7 @@ nfsd4_process_open2(struct svc_rqst *rqs
}
upgrade_out:
nfs4_inc_and_copy_stateid(&open->op_stateid, &stp->st_stid);
- up_read(&stp->st_rwsem);
+ mutex_unlock(&stp->st_mutex);

if (nfsd4_has_session(&resp->cstate)) {
if (open->op_deleg_want & NFS4_SHARE_WANT_NO_DELEG) {
@@ -4950,12 +4950,12 @@ static __be32 nfs4_seqid_op_checks(struc
* revoked delegations are kept only for free_stateid.
*/
return nfserr_bad_stateid;
- down_write(&stp->st_rwsem);
+ mutex_lock(&stp->st_mutex);
status = check_stateid_generation(stateid, &stp->st_stid.sc_stateid, nfsd4_has_session(cstate));
if (status == nfs_ok)
status = nfs4_check_fh(current_fh, &stp->st_stid);
if (status != nfs_ok)
- up_write(&stp->st_rwsem);
+ mutex_unlock(&stp->st_mutex);
return status;
}

@@ -5003,7 +5003,7 @@ static __be32 nfs4_preprocess_confirmed_
return status;
oo = openowner(stp->st_stateowner);
if (!(oo->oo_flags & NFS4_OO_CONFIRMED)) {
- up_write(&stp->st_rwsem);
+ mutex_unlock(&stp->st_mutex);
nfs4_put_stid(&stp->st_stid);
return nfserr_bad_stateid;
}
@@ -5035,12 +5035,12 @@ nfsd4_open_confirm(struct svc_rqst *rqst
oo = openowner(stp->st_stateowner);
status = nfserr_bad_stateid;
if (oo->oo_flags & NFS4_OO_CONFIRMED) {
- up_write(&stp->st_rwsem);
+ mutex_unlock(&stp->st_mutex);
goto put_stateid;
}
oo->oo_flags |= NFS4_OO_CONFIRMED;
nfs4_inc_and_copy_stateid(&oc->oc_resp_stateid, &stp->st_stid);
- up_write(&stp->st_rwsem);
+ mutex_unlock(&stp->st_mutex);
dprintk("NFSD: %s: success, seqid=%d stateid=" STATEID_FMT "\n",
__func__, oc->oc_seqid, STATEID_VAL(&stp->st_stid.sc_stateid));

@@ -5116,7 +5116,7 @@ nfsd4_open_downgrade(struct svc_rqst *rq
nfs4_inc_and_copy_stateid(&od->od_stateid, &stp->st_stid);
status = nfs_ok;
put_stateid:
- up_write(&stp->st_rwsem);
+ mutex_unlock(&stp->st_mutex);
nfs4_put_stid(&stp->st_stid);
out:
nfsd4_bump_seqid(cstate, status);
@@ -5169,7 +5169,7 @@ nfsd4_close(struct svc_rqst *rqstp, stru
if (status)
goto out;
nfs4_inc_and_copy_stateid(&close->cl_stateid, &stp->st_stid);
- up_write(&stp->st_rwsem);
+ mutex_unlock(&stp->st_mutex);

nfsd4_close_open_stateid(stp);

@@ -5395,7 +5395,7 @@ init_lock_stateid(struct nfs4_ol_stateid
stp->st_access_bmap = 0;
stp->st_deny_bmap = open_stp->st_deny_bmap;
stp->st_openstp = open_stp;
- init_rwsem(&stp->st_rwsem);
+ mutex_init(&stp->st_mutex);
list_add(&stp->st_locks, &open_stp->st_locks);
list_add(&stp->st_perstateowner, &lo->lo_owner.so_stateids);
spin_lock(&fp->fi_lock);
@@ -5564,7 +5564,7 @@ nfsd4_lock(struct svc_rqst *rqstp, struc
&open_stp, nn);
if (status)
goto out;
- up_write(&open_stp->st_rwsem);
+ mutex_unlock(&open_stp->st_mutex);
open_sop = openowner(open_stp->st_stateowner);
status = nfserr_bad_stateid;
if (!same_clid(&open_sop->oo_owner.so_client->cl_clientid,
@@ -5573,7 +5573,7 @@ nfsd4_lock(struct svc_rqst *rqstp, struc
status = lookup_or_create_lock_state(cstate, open_stp, lock,
&lock_stp, &new);
if (status == nfs_ok)
- down_write(&lock_stp->st_rwsem);
+ mutex_lock(&lock_stp->st_mutex);
} else {
status = nfs4_preprocess_seqid_op(cstate,
lock->lk_old_lock_seqid,
@@ -5677,7 +5677,7 @@ out:
seqid_mutating_err(ntohl(status)))
lock_sop->lo_owner.so_seqid++;

- up_write(&lock_stp->st_rwsem);
+ mutex_unlock(&lock_stp->st_mutex);

/*
* If this is a new, never-before-used stateid, and we are
@@ -5847,7 +5847,7 @@ nfsd4_locku(struct svc_rqst *rqstp, stru
fput:
fput(filp);
put_stateid:
- up_write(&stp->st_rwsem);
+ mutex_unlock(&stp->st_mutex);
nfs4_put_stid(&stp->st_stid);
out:
nfsd4_bump_seqid(cstate, status);
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -535,7 +535,7 @@ struct nfs4_ol_stateid {
unsigned char st_access_bmap;
unsigned char st_deny_bmap;
struct nfs4_ol_stateid *st_openstp;
- struct rw_semaphore st_rwsem;
+ struct mutex st_mutex;
};

static inline struct nfs4_ol_stateid *openlockstateid(struct nfs4_stid *s)