linux-kernel - [PATCH 3.16 097/178] ACPI / APEI: Add missing synchronize_rcu() on NOTIFY

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Message-ID: <lsq.1500213406.385729355@decadent.org.uk>
Date:   Sun, 16 Jul 2017 14:56:46 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        "James Morse" <james.morse@....com>,
        "Huang, Ying" <ying.huang@...el.com>
Subject: [PATCH 3.16 097/178] ACPI / APEI: Add missing synchronize_rcu()
 on NOTIFY_SCI removal

3.16.46-rc1 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: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/acpi/apei/ghes.c | 1 +
 1 file changed, 1 insertion(+)

--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -1020,6 +1020,7 @@ 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:
 		mutex_lock(&ghes_list_mutex);