linux-kernel - [PATCH 4.4 53/53] ACPI / APEI: Add missing synchronize_rcu() on NOTIFY

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Message-Id: <20170828080520.063921327@linuxfoundation.org>
Date:   Mon, 28 Aug 2017 10:05:58 +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, James Morse <james.morse@....com>,
        "Huang, Ying" <ying.huang@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: [PATCH 4.4 53/53] ACPI / APEI: Add missing synchronize_rcu() on NOTIFY_SCI removal

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: James Morse <james.morse@....com>

commit 7d64f82cceb21e6d95db312d284f5f195e120154 upstream.

When removing a GHES device notified by SCI, list_del_rcu() is used,
ghes_remove() should call synchronize_rcu() before it goes on to call
kfree(ghes), otherwise concurrent RCU readers may still hold this list
entry after it has been freed.

Signed-off-by: James Morse <james.morse@....com>
Reviewed-by: "Huang, Ying" <ying.huang@...el.com>
Fixes: 81e88fdc432a (ACPI, APEI, Generic Hardware Error Source POLL/IRQ/NMI notification type support)
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/acpi/apei/ghes.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -1067,6 +1067,7 @@ static int ghes_remove(struct platform_d
 		if (list_empty(&ghes_sci))
 			unregister_acpi_hed_notifier(&ghes_notifier_sci);
 		mutex_unlock(&ghes_list_mutex);
+		synchronize_rcu();
 		break;
 	case ACPI_HEST_NOTIFY_NMI:
 		ghes_nmi_remove(ghes);