linux-kernel - [PATCH] ipmi: Move remove_work to dedicated workqueue

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-next>] [day] [month] [year] [list]

Message-Id: <20211112165413.7747-1-ioanna-maria.alifieraki@canonical.com>
Date:   Fri, 12 Nov 2021 18:54:13 +0200
From:   Ioanna Alifieraki <ioanna-maria.alifieraki@...onical.com>
To:     linux-kernel@...r.kernel.org,
        openipmi-developer@...ts.sourceforge.net, minyard@....org,
        ioanna.alifieraki@...il.com
Subject: [PATCH] ipmi: Move remove_work to dedicated workqueue

Currently when removing an ipmi_user the removal is deferred as a work on
the system's workqueue. Although this guarantees the free operation will
occur in non atomic context, it can race with the ipmi_msghandler module
removal (see [1]) . In case a remove_user work is scheduled for removal
and shortly after ipmi_msghandler module is removed we can end up in a
situation where the module is removed fist and when the work is executed
the system crashes with :
BUG: unable to handle page fault for address: ffffffffc05c3450
PF: supervisor instruction fetch in kernel mode
PF: error_code(0x0010) - not-present page
because the pages of the module are gone. In cleanup_ipmi() there is no
easy way to detect if there are any pending works to flush them before
removing the module. This patch creates a separate workqueue and schedules
the remove_work works on it. When removing the module the workqueue is
flushed to avoid the race.

[1] https://bugs.launchpad.net/bugs/1950666

Cc: stable@...r.kernel.org
Fixes: 3b9a907223d7 (ipmi: fix sleep-in-atomic in free_user at cleanup SRCU user->release_barrier)
Signed-off-by: Ioanna Alifieraki <ioanna-maria.alifieraki@...onical.com>
---
 drivers/char/ipmi/ipmi_msghandler.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
index deed355422f4..9e0ad2ccd3e0 100644
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -191,6 +191,8 @@ struct ipmi_user {
 	struct work_struct remove_work;
 };

+struct workqueue_struct *remove_work_wq;
+
 static struct ipmi_user *acquire_ipmi_user(struct ipmi_user *user, int *index)
 	__acquires(user->release_barrier)
 {
@@ -1297,7 +1299,7 @@ static void free_user(struct kref *ref)
 	struct ipmi_user *user = container_of(ref, struct ipmi_user, refcount);

 	/* SRCU cleanup must happen in task context. */
-	schedule_work(&user->remove_work);
+	queue_work(remove_work_wq, &user->remove_work);
 }

 static void _ipmi_destroy_user(struct ipmi_user *user)
@@ -5383,6 +5385,8 @@ static int ipmi_init_msghandler(void)

 	atomic_notifier_chain_register(&panic_notifier_list, &panic_block);

+	remove_work_wq = create_singlethread_workqueue("ipmi-msghandler-remove-wq");
+
 	initialized = true;

 out:
@@ -5408,6 +5412,9 @@ static void __exit cleanup_ipmi(void)
 	int count;

 	if (initialized) {
+		flush_workqueue(remove_work_wq);
+		destroy_workqueue(remove_work_wq);
+
 		atomic_notifier_chain_unregister(&panic_notifier_list,
 						 &panic_block);

-- 
2.17.1