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nfsd: fix race that grants unrecallable delegation 

If nfs4_setlease succesfully acquires a new delegation, then another
task breaks the delegation before we reach hash_delegation_locked, then
the breaking task will see an empty fi_delegations list and do nothing.
The client will receive an open reply incorrectly granting a delegation
and will never receive a recall.

Move more of the delegation fields to be protected by the fi_lock. It's
more granular than the state_lock and in later patches we'll want to
be able to rely on it in addition to the state_lock.

Attempt to acquire a delegation. If that succeeds, take the spinlocks
and then check to see if the file has had a conflict show up since then.
If it has, then we assume that the lease is no longer valid and that
we shouldn't hand out a delegation.

There's also one more potential (but very unlikely) problem. If the
lease is broken before the delegation is hashed, then it could leak.
In the event that the fi_delegations list is empty, reset the
fl_break_time to jiffies so that it's cleaned up ASAP by
the normal lease handling code.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Jeff Layton 2014-07-21 09:34:57 -04:00 committed by J. Bruce Fields
parent 57a3714421
commit 417c6629b2
1 changed files with 68 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

90
fs/nfsd/nfs4state.c
View File

@ -624,6 +624,8 @@ nfs4_put_delegation(struct nfs4_delegation *dp)
static void nfs4_put_deleg_lease(struct nfs4_file *fp)
{
lockdep_assert_held(&state_lock);
if (!fp->fi_lease)
return;
if (atomic_dec_and_test(&fp->fi_delegees)) {
@ -643,11 +645,10 @@ static void
hash_delegation_locked(struct nfs4_delegation *dp, struct nfs4_file *fp)
{
lockdep_assert_held(&state_lock);
lockdep_assert_held(&fp->fi_lock);
dp->dl_stid.sc_type = NFS4_DELEG_STID;
spin_lock(&fp->fi_lock);
list_add(&dp->dl_perfile, &fp->fi_delegations);
spin_unlock(&fp->fi_lock);
list_add(&dp->dl_perclnt, &dp->dl_stid.sc_client->cl_delegations);
}
@ -659,17 +660,18 @@ unhash_delegation(struct nfs4_delegation *dp)
spin_lock(&state_lock);
dp->dl_stid.sc_type = NFS4_CLOSED_DELEG_STID;
spin_lock(&fp->fi_lock);
list_del_init(&dp->dl_perclnt);
list_del_init(&dp->dl_recall_lru);
spin_lock(&fp->fi_lock);
list_del_init(&dp->dl_perfile);
spin_unlock(&fp->fi_lock);
spin_unlock(&state_lock);
if (fp) {
nfs4_put_deleg_lease(fp);
put_nfs4_file(fp);
dp->dl_file = NULL;
}
spin_unlock(&state_lock);
if (fp)
put_nfs4_file(fp);
}
static void destroy_revoked_delegation(struct nfs4_delegation *dp)
@ -3141,8 +3143,17 @@ static void nfsd_break_deleg_cb(struct file_lock *fl)
*/
fl->fl_break_time = 0;
fp->fi_had_conflict = true;
spin_lock(&fp->fi_lock);
fp->fi_had_conflict = true;
/*
* If there are no delegations on the list, then we can't count on this
* lease ever being cleaned up. Set the fl_break_time to jiffies so that
* time_out_leases will do it ASAP. The fact that fi_had_conflict is now
* true should keep any new delegations from being hashed.
*/
if (list_empty(&fp->fi_delegations))
fl->fl_break_time = jiffies;
else
list_for_each_entry(dp, &fp->fi_delegations, dl_perfile)
nfsd_break_one_deleg(dp);
spin_unlock(&fp->fi_lock);
@ -3491,46 +3502,77 @@ static int nfs4_setlease(struct nfs4_delegation *dp)
{
struct nfs4_file *fp = dp->dl_file;
struct file_lock *fl;
int status;
struct file *filp;
int status = 0;
fl = nfs4_alloc_init_lease(fp, NFS4_OPEN_DELEGATE_READ);
if (!fl)
return -ENOMEM;
fl->fl_file = find_readable_file(fp);
status = vfs_setlease(fl->fl_file, fl->fl_type, &fl);
if (status)
goto out_free;
fp->fi_lease = fl;
fp->fi_deleg_file = fl->fl_file;
atomic_set(&fp->fi_delegees, 1);
filp = find_readable_file(fp);
if (!filp) {
/* We should always have a readable file here */
WARN_ON_ONCE(1);
return -EBADF;
}
fl->fl_file = filp;
status = vfs_setlease(filp, fl->fl_type, &fl);
if (status) {
locks_free_lock(fl);
goto out_fput;
}
spin_lock(&state_lock);
spin_lock(&fp->fi_lock);
/* Did the lease get broken before we took the lock? */
status = -EAGAIN;
if (fp->fi_had_conflict)
goto out_unlock;
/* Race breaker */
if (fp->fi_lease) {
status = 0;
atomic_inc(&fp->fi_delegees);
hash_delegation_locked(dp, fp);
goto out_unlock;
}
fp->fi_lease = fl;
fp->fi_deleg_file = filp;
atomic_set(&fp->fi_delegees, 1);
hash_delegation_locked(dp, fp);
spin_unlock(&fp->fi_lock);
spin_unlock(&state_lock);
return 0;
out_free:
if (fl->fl_file)
fput(fl->fl_file);
locks_free_lock(fl);
out_unlock:
spin_unlock(&fp->fi_lock);
spin_unlock(&state_lock);
out_fput:
fput(filp);
return status;
}
static int nfs4_set_delegation(struct nfs4_delegation *dp, struct nfs4_file *fp)
{
int status = 0;
if (fp->fi_had_conflict)
return -EAGAIN;
get_nfs4_file(fp);
dp->dl_file = fp;
if (!fp->fi_lease)
return nfs4_setlease(dp);
spin_lock(&state_lock);
spin_lock(&fp->fi_lock);
dp->dl_file = fp;
if (!fp->fi_lease) {
spin_unlock(&fp->fi_lock);
spin_unlock(&state_lock);
return nfs4_setlease(dp);
}
atomic_inc(&fp->fi_delegees);
if (fp->fi_had_conflict) {
spin_unlock(&state_lock);
return -EAGAIN;
status = -EAGAIN;
goto out_unlock;
}
hash_delegation_locked(dp, fp);
out_unlock:
spin_unlock(&fp->fi_lock);
spin_unlock(&state_lock);
return 0;
return status;
}
static void nfsd4_open_deleg_none_ext(struct nfsd4_open *open, int status)