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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, "Yan, Zheng" <zyan@redhat.com>,
        Jeff Layton <jlayton@kernel.org>,
        Ilya Dryomov <idryomov@gmail.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 015/168] ceph: dont skip updating wanted caps when cap is stale
Date:   Tue, 28 Apr 2020 20:23:09 +0200
Message-Id: <20200428182233.626844888@linuxfoundation.org>
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From: Yan, Zheng <zyan@redhat.com>

[ Upstream commit 0aa971b6fd3f92afef6afe24ef78d9bb14471519 ]

1. try_get_cap_refs() fails to get caps and finds that mds_wanted
   does not include what it wants. It returns -ESTALE.
2. ceph_get_caps() calls ceph_renew_caps(). ceph_renew_caps() finds
   that inode has cap, so it calls ceph_check_caps().
3. ceph_check_caps() finds that issued caps (without checking if it's
   stale) already includes caps wanted by open file, so it skips
   updating wanted caps.

Above events can cause an infinite loop inside ceph_get_caps().

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/ceph/caps.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index f5a38910a82bf..703945cce0e5d 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -1976,8 +1976,12 @@ retry_locked:
 		}
 
 		/* want more caps from mds? */
-		if (want & ~(cap->mds_wanted | cap->issued))
-			goto ack;
+		if (want & ~cap->mds_wanted) {
+			if (want & ~(cap->mds_wanted | cap->issued))
+				goto ack;
+			if (!__cap_is_valid(cap))
+				goto ack;
+		}
 
 		/* things we might delay */
 		if ((cap->issued & ~retain) == 0)
-- 
2.20.1