> On Aug 8, 2016, at 9:19 AM, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
>
> On Sun, 2016-08-07 at 18:22 -0400, Jeff Layton wrote:
>> On Sun, 2016-08-07 at 14:53 -0400, Chuck Lever wrote:
>>>
>>> When running LTP's nfslock01 test, the Linux client can send a LOCK
>>> and a FREE_STATEID request at the same time. The LOCK uses the same
>>> lockowner as the stateid sent in the FREE_STATEID request.
>>>
>>> The outcome is:
>>>
>>> Frame 115025 C FREE_STATEID stateid 2/A
>>> Frame 115026 C LOCK offset 672128 len 64
>>> Frame 115029 R FREE_STATEID NFS4_OK
>>> Frame 115030 R LOCK stateid 3/A
>
> Oh, to be clear here -- I assume this a lk_is_new lock (with an open
> stateid in it). Right?
Opcode: LOCK (12)
locktype: WRITEW_LT (4)
reclaim?: No
offset: 672000
length: 64
new lock owner?: Yes
seqid: 0x00000000
stateid
[StateID Hash: 0x6f7e]
seqid: 0x00000002
Data: a95169579501000007000000
lock_seqid: 0x00000000
Owner
clientid: 0xa951695795010000
Data: <DATA>
length: 20
contents: <DATA>
The first appearance of that stateid is in an earlier OPEN reply:
Opcode: OPEN (18)
Status: NFS4_OK (0)
stateid
[StateID Hash: 0x6f7e]
seqid: 0x00000002
Data: a95169579501000007000000
change_info
Atomic: No
changeid (before): 0
changeid (after): 0
result flags: 0x00000004, locktype posix
.... .... .... .... .... .... .... ..0. = confirm: False
.... .... .... .... .... .... .... .1.. = locktype posix: True
.... .... .... .... .... .... .... 0... = preserve unlinked: False
.... .... .... .... .... .... ..0. .... = may notify lock: False
Delegation Type: OPEN_DELEGATE_NONE (0)
>>> Frame 115034 C WRITE stateid 0/A offset 672128 len 64
>>> Frame 115038 R WRITE NFS4ERR_BAD_STATEID
>>>
>>> In other words, the server returns stateid A in a successful LOCK
>>> reply, but it has already released it. Subsequent uses of the
>>> stateid 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@xxxxxxxxxx>
>>> Fix-suggested-by: Jeff Layton <jlayton@xxxxxxxxxx>
>>> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
>>> ---
>>> fs/nfsd/nfs4state.c | 19 ++++++++++++-------
>>> 1 file changed, 12 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
>>> index b921123..07dc1aa 100644
>>> --- a/fs/nfsd/nfs4state.c
>>> +++ b/fs/nfsd/nfs4state.c
>>> @@ -4911,19 +4911,20 @@ nfsd4_free_stateid(struct svc_rqst *rqstp,
>>> struct nfsd4_compound_state *cstate,
>>> ret = nfserr_locks_held;
>>> break;
>>> case NFS4_LOCK_STID:
>>> + atomic_inc(&s->sc_count);
>>> + spin_unlock(&cl->cl_lock);
>>> + stp = openlockstateid(s);
>>> + mutex_lock(&stp->st_mutex);
>>> ret = check_stateid_generation(stateid, &s-
>>>>
>>>> sc_stateid, 1);
>>> if (ret)
>>> - break;
>>> - stp = openlockstateid(s);
>>> + goto out_mutex_unlock;
>>> ret = nfserr_locks_held;
>>> if (check_for_locks(stp->st_stid.sc_file,
>>> lockowner(stp-
>>>> st_stateowner)))
>>> - break;
>>> - WARN_ON(!unhash_lock_stateid(stp));
>>> - spin_unlock(&cl->cl_lock);
>>> - nfs4_put_stid(s);
>>> + goto out_mutex_unlock;
>>> + release_lock_stateid(stp);
>>> ret = nfs_ok;
>>> - goto out;
>>> + goto out_mutex_unlock;
>>> case NFS4_REVOKED_DELEG_STID:
>>> dp = delegstateid(s);
>>> list_del_init(&dp->dl_recall_lru);
>>> @@ -4937,6 +4938,10 @@ out_unlock:
>>> spin_unlock(&cl->cl_lock);
>>> out:
>>> return ret;
>>> +out_mutex_unlock:
>>> + mutex_unlock(&stp->st_mutex);
>>> + nfs4_put_stid(s);
>>> + goto out;
>>> }
>>>
>>> static inline int
>>>
>>>
>>
>> Looks good to me.
>>
>> Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
>
> Hmm...I think this is not a complete fix though. We also need something
> like this patch:
OK, I'll create a series and add this patch.
> --------------[snip]---------------
>
> [PATCH] nfsd: don't return an already-unhashed lock stateid after
> taking mutex
>
> nfsd4_lock will take the st_mutex before working with the stateid it
> gets, but between the time when we drop the cl_lock and take the mutex,
> the stateid could become unhashed (a'la FREE_STATEID). If that happens
> the lock stateid returned to the client will be forgotten.
>
> Fix this by first moving the st_mutex acquisition into
> lookup_or_create_lock_state. Then, have it check to see if the lock
> stateid is still hashed after taking the mutex. If it's not, then put
> the stateid and try the find/create again.
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> fs/nfsd/nfs4state.c | 25 ++++++++++++++++++++-----
> 1 file changed, 20 insertions(+), 5 deletions(-)
>
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 5d6a28af0f42..1235b1661703 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -5653,7 +5653,7 @@ static __be32
> lookup_or_create_lock_state(struct nfsd4_compound_state *cstate,
> struct nfs4_ol_stateid *ost,
> struct nfsd4_lock *lock,
> - struct nfs4_ol_stateid **lst, bool *new)
> + struct nfs4_ol_stateid **plst, bool *new)
> {
> __be32 status;
> struct nfs4_file *fi = ost->st_stid.sc_file;
> @@ -5661,7 +5661,9 @@ lookup_or_create_lock_state(struct nfsd4_compound_state *cstate,
> struct nfs4_client *cl = oo->oo_owner.so_client;
> struct inode *inode = d_inode(cstate->current_fh.fh_dentry);
> struct nfs4_lockowner *lo;
> + struct nfs4_ol_stateid *lst;
> unsigned int strhashval;
> + bool hashed;
>
> lo = find_lockowner_str(cl, &lock->lk_new_owner);
> if (!lo) {
> @@ -5677,12 +5679,27 @@ lookup_or_create_lock_state(struct nfsd4_compound_state *cstate,
> goto out;
> }
>
> - *lst = find_or_create_lock_stateid(lo, fi, inode, ost, new);
> - if (*lst == NULL) {
> +retry:
> + lst = find_or_create_lock_stateid(lo, fi, inode, ost, new);
> + if (lst == NULL) {
> status = nfserr_jukebox;
> goto out;
> }
> +
> + mutex_lock(&lst->st_mutex);
> +
> + /* See if it's still hashed to avoid race with FREE_STATEID */
> + spin_lock(&cl->cl_lock);
> + hashed = list_empty(&lst->st_perfile);
> + spin_unlock(&cl->cl_lock);
> +
> + if (!hashed) {
> + mutex_unlock(&lst->st_mutex);
> + nfs4_put_stid(&lst->st_stid);
> + goto retry;
> + }
> status = nfs_ok;
> + *plst = lst;
> out:
> nfs4_put_stateowner(&lo->lo_owner);
> return status;
> @@ -5752,8 +5769,6 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
> goto out;
> status = lookup_or_create_lock_state(cstate, open_stp, lock,
> &lock_stp, &new);
> - if (status == nfs_ok)
> - mutex_lock(&lock_stp->st_mutex);
> } else {
> status = nfs4_preprocess_seqid_op(cstate,
> lock->lk_old_lock_seqid,
> --
> 2.7.4
--
Chuck Lever
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