Commit ce3c4ad7 authored by Chuck Lever's avatar Chuck Lever
Browse files

NFSD: Fix possible sleep during nfsd4_release_lockowner() 



nfsd4_release_lockowner() holds clp->cl_lock when it calls
check_for_locks(). However, check_for_locks() calls nfsd_file_get()
/ nfsd_file_put() to access the backing inode's flc_posix list, and
nfsd_file_put() can sleep if the inode was recently removed.

Let's instead rely on the stateowner's reference count to gate
whether the release is permitted. This should be a reliable
indication of locks-in-use since file lock operations and
->lm_get_owner take appropriate references, which are released
appropriately when file locks are removed.

Reported-by: default avatarDai Ngo <dai.ngo@oracle.com>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
Cc: stable@vger.kernel.org
parent fd5e363e

fs/nfsd/nfs4state.c

+4 −8
Original line number Diff line number Diff line
@@ -7557,16 +7557,12 @@ nfsd4_release_lockowner(struct svc_rqst *rqstp, 
		if (sop->so_is_open_owner || !same_owner_str(sop, owner))

			continue;



		/* see if there are still any locks associated with it */

		lo = lockowner(sop);

		list_for_each_entry(stp, &sop->so_stateids, st_perstateowner) {

			if (check_for_locks(stp->st_stid.sc_file, lo)) {

				status = nfserr_locks_held;

		if (atomic_read(&sop->so_count) != 1) {

			spin_unlock(&clp->cl_lock);

				return status;

			}

			return nfserr_locks_held;

		}



		lo = lockowner(sop);

		nfs4_get_stateowner(sop);

		break;

	}