linux-kernel - [PATCH] block: prevent sending events from removed device

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Date:   Wed, 30 Jun 2021 08:09:39 +0000
From:   Christian Löhle <CLoehle@...erstone.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        Christian Löhle <CLoehle@...erstone.com>
Subject: [PATCH] block: prevent sending events from removed device

Skip kobject_uevent_env in case the associated kobject
no longer exists, as calling kobject_uevent_env with
NULL is not safe.

Signed-off-by: Christian Loehle <cloehle@...erstone.com>
---
 block/genhd.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index 9f8cb7beaad1..46629fbe23ae 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1655,8 +1655,16 @@ static void disk_check_events(struct disk_events *ev,
 		    (disk->event_flags & DISK_EVENT_FLAG_UEVENT))
 			envp[nr_events++] = disk_uevents[i];
 
-	if (nr_events)
-		kobject_uevent_env(&disk_to_dev(disk)->kobj, KOBJ_CHANGE, envp);
+	if (nr_events) {
+		struct kobject *dev_kobj = kobject_get(&disk_to_dev(disk)->kobj);
+		/* The device kobject might have been removed in the
+		 * meantime, so check for it first.
+		 * If it was removed there is no need to signal events
+		 */
+		if (!dev_kobj)
+			kobject_uevent_env(dev_kobj, KOBJ_CHANGE, envp);
+		kobject_put(dev_kobj);
+	}
 }
 
 /*
-- 
2.32.0

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