[PATCH v2 2/6] NFSD: Fix possible sleep during nfsd4_release_lockowner()

From: Chuck Lever <chuck.lever@oracle.com>
To: linux-nfs@vger.kernel.org
Subject: [PATCH v2 2/6] NFSD: Fix possible sleep during nfsd4_release_lockowner()
Date: Tue, 24 May 2022 14:57:04 -0400	[thread overview]
Message-ID: <165341862441.3187.2513226782679879324.stgit@bazille.1015granger.net> (raw)
In-Reply-To: <165341832236.3187.8388683641228729897.stgit@bazille.1015granger.net>

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.

Instead, use the recently introduced counter field in struct
nfs4_lockowner that keeps track of how many locks are associated
with that lock owner.

Reported-by: Dai Ngo <dai.ngo@oracle.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: stable@vger.kernel.org
---
 fs/nfsd/nfs4state.c |   11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index d2d9748eaca6..7cedb0da888d 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -7563,16 +7563,11 @@ 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;
-				spin_unlock(&clp->cl_lock);
-				return status;
-			}
+		if (atomic_read(&lo->lo_lockcnt) != 0) {
+			spin_unlock(&clp->cl_lock);
+			return nfserr_locks_held;
 		}
-
 		nfs4_get_stateowner(sop);
 		break;
 	}


