linux-kernel - [PATCH 19/19] drbd: fix refcount error during detach of an already failed disk

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1438255314-14877-20-git-send-email-philipp.reisner@linbit.com>
Date:	Thu, 30 Jul 2015 13:21:54 +0200
From:	Philipp Reisner <philipp.reisner@...bit.com>
To:	linux-kernel@...r.kernel.org, Jens Axboe <axboe@...nel.dk>
Cc:	drbd-dev@...ts.linbit.com
Subject: [PATCH 19/19] drbd: fix refcount error during detach of an already failed disk

From: Lars Ellenberg <lars.ellenberg@...bit.com>

A D_FAILED disk transitions as quickly as possible to
D_DISKLESS. But in the "unresponsive local disk" case,
there remains a time window where a administrative detach command could
find the disk already failed, but some internal meta data IO against the
unresponsive local disk still pending.

In that case, drbd_md_get_buffer() will return NULL.
Don't unconditionally call drbd_md_put_buffer(), or it will cause
refcount imbalance, and prevent any further re-attach on this volume
(until it is deleted and re-created).

Signed-off-by: Philipp Reisner <philipp.reisner@...bit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@...bit.com>
---
 drivers/block/drbd/drbd_nl.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 7229d8e..4c8d8e7 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1915,6 +1915,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
 static int adm_detach(struct drbd_device *device, int force)
 {
 	enum drbd_state_rv retcode;
+	void *buffer;
 	int ret;
 
 	if (force) {
@@ -1925,9 +1926,12 @@ static int adm_detach(struct drbd_device *device, int force)
 	}
 
 	drbd_suspend_io(device); /* so no-one is stuck in drbd_al_begin_io */
-	drbd_md_get_buffer(device, __func__); /* make sure there is no in-flight meta-data IO */
-	retcode = drbd_request_state(device, NS(disk, D_FAILED));
-	drbd_md_put_buffer(device);
+	buffer = drbd_md_get_buffer(device, __func__); /* make sure there is no in-flight meta-data IO */
+	if (buffer) {
+		retcode = drbd_request_state(device, NS(disk, D_FAILED));
+		drbd_md_put_buffer(device);
+	} else /* already <= D_FAILED */
+		retcode = SS_NOTHING_TO_DO;
 	/* D_FAILED will transition to DISKLESS. */
 	drbd_resume_io(device);
 	ret = wait_event_interruptible(device->misc_wait,
-- 
1.9.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/