linux-kernel - [PATCH 4.19 053/245] ACPI: EC: Reference count query handlers under lock

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: <20200929105949.580680387@linuxfoundation.org>
Date:   Tue, 29 Sep 2020 12:58:24 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 053/245] ACPI: EC: Reference count query handlers under lock

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

[ Upstream commit 3df663a147fe077a6ee8444ec626738946e65547 ]

There is a race condition in acpi_ec_get_query_handler()
theoretically allowing query handlers to go away before refernce
counting them.

In order to avoid it, call kref_get() on query handlers under
ec->mutex.

Also simplify the code a bit while at it.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/acpi/ec.c | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 49e16f0090957..9415a0041aaf7 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -1080,29 +1080,21 @@ void acpi_ec_dispatch_gpe(void)
 /* --------------------------------------------------------------------------
                                 Event Management
    -------------------------------------------------------------------------- */
-static struct acpi_ec_query_handler *
-acpi_ec_get_query_handler(struct acpi_ec_query_handler *handler)
-{
-	if (handler)
-		kref_get(&handler->kref);
-	return handler;
-}
-
 static struct acpi_ec_query_handler *
 acpi_ec_get_query_handler_by_value(struct acpi_ec *ec, u8 value)
 {
 	struct acpi_ec_query_handler *handler;
-	bool found = false;
 
 	mutex_lock(&ec->mutex);
 	list_for_each_entry(handler, &ec->list, node) {
 		if (value == handler->query_bit) {
-			found = true;
-			break;
+			kref_get(&handler->kref);
+			mutex_unlock(&ec->mutex);
+			return handler;
 		}
 	}
 	mutex_unlock(&ec->mutex);
-	return found ? acpi_ec_get_query_handler(handler) : NULL;
+	return NULL;
 }
 
 static void acpi_ec_query_handler_release(struct kref *kref)
-- 
2.25.1