linux-kernel - [PATCH 5.8 375/464] ocfs2: fix unbalanced locking

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Date:   Mon, 17 Aug 2020 17:15:28 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, "Pavel Machek (CIP)" <pavel@...x.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joseph Qi <joseph.qi@...ux.alibaba.com>,
        Mark Fasheh <mark@...heh.com>,
        Joel Becker <jlbec@...lplan.org>,
        Junxiao Bi <junxiao.bi@...cle.com>,
        Changwei Ge <gechangwei@...e.cn>, Gang He <ghe@...e.com>,
        Jun Piao <piaojun@...wei.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.8 375/464] ocfs2: fix unbalanced locking

From: Pavel Machek <pavel@....cz>

[ Upstream commit 57c720d4144a9c2b88105c3e8f7b0e97e4b5cc93 ]

Based on what fails, function can return with nfs_sync_rwlock either
locked or unlocked. That can not be right.

Always return with lock unlocked on error.

Fixes: 4cd9973f9ff6 ("ocfs2: avoid inode removal while nfsd is accessing it")
Signed-off-by: Pavel Machek (CIP) <pavel@...x.de>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Reviewed-by: Joseph Qi <joseph.qi@...ux.alibaba.com>
Reviewed-by: Andrew Morton <akpm@...ux-foundation.org>
Cc: Mark Fasheh <mark@...heh.com>
Cc: Joel Becker <jlbec@...lplan.org>
Cc: Junxiao Bi <junxiao.bi@...cle.com>
Cc: Changwei Ge <gechangwei@...e.cn>
Cc: Gang He <ghe@...e.com>
Cc: Jun Piao <piaojun@...wei.com>
Link: http://lkml.kernel.org/r/20200724124443.GA28164@duo.ucw.cz
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/ocfs2/dlmglue.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
index 751bc4dc74663..8e3a369086dbd 100644
--- a/fs/ocfs2/dlmglue.c
+++ b/fs/ocfs2/dlmglue.c
@@ -2871,9 +2871,15 @@ int ocfs2_nfs_sync_lock(struct ocfs2_super *osb, int ex)
 
 	status = ocfs2_cluster_lock(osb, lockres, ex ? LKM_EXMODE : LKM_PRMODE,
 				    0, 0);
-	if (status < 0)
+	if (status < 0) {
 		mlog(ML_ERROR, "lock on nfs sync lock failed %d\n", status);
 
+		if (ex)
+			up_write(&osb->nfs_sync_rwlock);
+		else
+			up_read(&osb->nfs_sync_rwlock);
+	}
+
 	return status;
 }
 
-- 
2.25.1