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nfsd: Fix race between FREE_STATEID and LOCK

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When running LTP's nfslock01 test, the Linux client can send a LOCK
and a FREE_STATEID request at the same time. The outcome is:

Frame 324    R OPEN stateid [2,O]

Frame 115004 C LOCK lockowner_is_new stateid [2,O] offset 672000 len 64
Frame 115008 R LOCK stateid [1,L]
Frame 115012 C WRITE stateid [0,L] offset 672000 len 64
Frame 115016 R WRITE NFS4_OK
Frame 115019 C LOCKU stateid [1,L] offset 672000 len 64
Frame 115022 R LOCKU NFS4_OK
Frame 115025 C FREE_STATEID stateid [2,L]
Frame 115026 C LOCK lockowner_is_new stateid [2,O] offset 672128 len 64
Frame 115029 R FREE_STATEID NFS4_OK
Frame 115030 R LOCK stateid [3,L]
Frame 115034 C WRITE stateid [0,L] offset 672128 len 64
Frame 115038 R WRITE NFS4ERR_BAD_STATEID

In other words, the server returns stateid L in a successful LOCK
reply, but it has already released it. Subsequent uses of stateid L
fail.

To address this, protect the generation check in nfsd4_free_stateid
with the st_mutex. This should guarantee that only one of two
outcomes occurs: either LOCK returns a fresh valid stateid, or
FREE_STATEID returns NFS4ERR_LOCKS_HELD.

Reported-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Fix-suggested-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Chuck Lever 2016-08-11 10:37:30 -04:00 committed by J. Bruce Fields
parent 502aa0a5be
commit 42691398be
1 changed files with 28 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
fs/nfsd/nfs4state.c
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@ -4903,6 +4903,32 @@ nfsd4_test_stateid(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
return nfs_ok;
}
static __be32
nfsd4_free_lock_stateid(stateid_t *stateid, struct nfs4_stid *s)
{
struct nfs4_ol_stateid *stp = openlockstateid(s);
__be32 ret;
mutex_lock(&stp->st_mutex);
ret = check_stateid_generation(stateid, &s->sc_stateid, 1);
if (ret)
goto out;
ret = nfserr_locks_held;
if (check_for_locks(stp->st_stid.sc_file,
lockowner(stp->st_stateowner)))
goto out;
release_lock_stateid(stp);
ret = nfs_ok;
out:
mutex_unlock(&stp->st_mutex);
nfs4_put_stid(s);
return ret;
}
__be32
nfsd4_free_stateid(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
struct nfsd4_free_stateid *free_stateid)
@ -4910,7 +4936,6 @@ nfsd4_free_stateid(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
stateid_t *stateid = &free_stateid->fr_stateid;
struct nfs4_stid *s;
struct nfs4_delegation *dp;
struct nfs4_ol_stateid *stp;
struct nfs4_client *cl = cstate->session->se_client;
__be32 ret = nfserr_bad_stateid;
@ -4929,18 +4954,9 @@ nfsd4_free_stateid(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
ret = nfserr_locks_held;
break;
case NFS4_LOCK_STID:
ret = check_stateid_generation(stateid, &s->sc_stateid, 1);
if (ret)
break;
stp = openlockstateid(s);
ret = nfserr_locks_held;
if (check_for_locks(stp->st_stid.sc_file,
lockowner(stp->st_stateowner)))
break;
WARN_ON(!unhash_lock_stateid(stp));
atomic_inc(&s->sc_count);
spin_unlock(&cl->cl_lock);
nfs4_put_stid(s);
ret = nfs_ok;
ret = nfsd4_free_lock_stateid(stateid, s);
goto out;
case NFS4_REVOKED_DELEG_STID:
dp = delegstateid(s);