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nfsd: don't return an unhashed lock stateid after taking mutex

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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@redhat.com>
Tested-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Cc: stable@vger.kernel.org # feb9dad5 nfsd: Always lock state exclusively.
Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Jeff Layton 2016-08-11 10:37:39 -04:00 committed by J. Bruce Fields
parent 42691398be
commit dd257933fa
1 changed files with 20 additions and 5 deletions
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25
fs/nfsd/nfs4state.c
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@ -5523,7 +5523,7 @@ 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;
@ -5531,7 +5531,9 @@ 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) {
@ -5547,12 +5549,27 @@ 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;
@ -5619,8 +5636,6 @@ 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,