linux-kernel - [PATCH] ceph: fix cap ref leak via netfs init

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Message-ID: <20241003010512.58559-1-batrick@batbytes.com>
Date: Wed,  2 Oct 2024 21:05:12 -0400
From: Patrick Donnelly <batrick@...bytes.com>
To: Xiubo Li <xiubli@...hat.com>,
	Ilya Dryomov <idryomov@...il.com>,
	Jeff Layton <jlayton@...nel.org>,
	David Howells <dhowells@...hat.com>
Cc: Patrick Donnelly <pdonnell@...hat.com>,
	stable@...r.kernel.org,
	ceph-devel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] ceph: fix cap ref leak via netfs init_request

From: Patrick Donnelly <pdonnell@...hat.com>

Log recovered from a user's cluster:

    <7>[ 5413.970692] ceph:  get_cap_refs 00000000958c114b ret 1 got Fr
    <7>[ 5413.970695] ceph:  start_read 00000000958c114b, no cache cap
    ...
    <7>[ 5473.934609] ceph:   my wanted = Fr, used = Fr, dirty -
    <7>[ 5473.934616] ceph:  revocation: pAsLsXsFr -> pAsLsXs (revoking Fr)
    <7>[ 5473.934632] ceph:  __ceph_caps_issued 00000000958c114b cap 00000000f7784259 issued pAsLsXs
    <7>[ 5473.934638] ceph:  check_caps 10000000e68.fffffffffffffffe file_want - used Fr dirty - flushing - issued pAsLsXs revoking Fr retain pAsLsXsFsr  AUTHONLY NOINVAL FLUSH_FORCE

The MDS subsequently complains that the kernel client is late releasing caps.

Approximately, a series of changes to this code by the three commits cited
below resulted in subtle resource cleanup to be missed. The main culprit is the
change in error handling in 2d31604 which meant that a failure in init_request
would no longer cause cleanup to be called. That would prevent the
ceph_put_cap_refs which would cleanup the leaked cap ref.

Closes: https://tracker.ceph.com/issues/67008
Fixes: 49870056005ca9387e5ee31451991491f99cc45f ("ceph: convert ceph_readpages to ceph_readahead")
Fixes: 2de160417315b8d64455fe03e9bb7d3308ac3281 ("netfs: Change ->init_request() to return an error code")
Fixes: a5c9dc4451394b2854493944dcc0ff71af9705a3 ("ceph: Make ceph_init_request() check caps on readahead")
Signed-off-by: Patrick Donnelly <pdonnell@...hat.com>
Cc: stable@...r.kernel.org
---
 fs/ceph/addr.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 53fef258c2bc..702c6a730b70 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -489,8 +489,11 @@ static int ceph_init_request(struct netfs_io_request *rreq, struct file *file)
 	rreq->io_streams[0].sreq_max_len = fsc->mount_options->rsize;
 
 out:
-	if (ret < 0)
+	if (ret < 0) {
+		if (got)
+			ceph_put_cap_refs(ceph_inode(inode), got);
 		kfree(priv);
+	}
 
 	return ret;
 }

base-commit: e32cde8d2bd7d251a8f9b434143977ddf13dcec6
-- 
Patrick Donnelly, Ph.D.
He / Him / His
Red Hat Partner Engineer
IBM, Inc.
GPG: 19F28A586F808C2402351B93C3301A3E258DD79D