On Tue, 2021-11-23 at 10:59 -0500, J. Bruce Fields wrote:
> On Tue, Nov 23, 2021 at 07:22:23AM -0500, Jeff Layton wrote:
> > Vasily reported a case where vfs_lock_file took a very long time to
> > return (longer than a lease period). The laundromat eventually ran and
> > reaped the thing and when the vfs_lock_file returned, it ended up
> > accessing freed memory.
>
> By the way, once we've called vfs_lock_file(), is there anything
> preventing nfsd4_cb_notify_lock_release() from freeing nbl before we get
> here?
>
No, I don't think there is. Good catch.
Hmm...the only way I can see to fix that would be to add a refcount to
these things, in which case we probably don't need this patch since it
would prevent the original issue as well...
> >
> > Don't put entries onto the LRU until vfs_lock_file returns.
> >
> > Reported-by: Vasily Averin <vvs@xxxxxxxxxxxxx>
> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> > ---
> > fs/nfsd/nfs4state.c | 6 ++++--
> > 1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > index bfad94c70b84..8cfef84b9355 100644
> > --- a/fs/nfsd/nfs4state.c
> > +++ b/fs/nfsd/nfs4state.c
> > @@ -6966,10 +6966,8 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
> > }
> >
> > if (fl_flags & FL_SLEEP) {
> > - nbl->nbl_time = ktime_get_boottime_seconds();
> > spin_lock(&nn->blocked_locks_lock);
> > list_add_tail(&nbl->nbl_list, &lock_sop->lo_blocked);
> > - list_add_tail(&nbl->nbl_lru, &nn->blocked_locks_lru);
> > spin_unlock(&nn->blocked_locks_lock);
> > }
> >
> > @@ -6982,6 +6980,10 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
> > nn->somebody_reclaimed = true;
> > break;
> > case FILE_LOCK_DEFERRED:
> > + nbl->nbl_time = ktime_get_boottime_seconds();
> > + spin_lock(&nn->blocked_locks_lock);
> > + list_add_tail(&nbl->nbl_lru, &nn->blocked_locks_lru);
> > + spin_unlock(&nn->blocked_locks_lock);
> > nbl = NULL;
> > fallthrough;
> > case -EAGAIN: /* conflock holds conflicting lock */
> > --
> > 2.33.1
--
Jeff Layton <jlayton@xxxxxxxxxx>
