linux-kernel - [PATCH 3.10 123/139] ACPI / APEI: Add missing synchronize_rcu() on NOTIFY

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Message-Id: <1509571624-5001-24-git-send-email-w@1wt.eu>
Date:   Wed,  1 Nov 2017 22:26:48 +0100
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     James Morse <james.morse@....com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 123/139] ACPI / APEI: Add missing synchronize_rcu() on NOTIFY_SCI removal

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: Willy Tarreau <w@....eu>
---
 drivers/acpi/apei/ghes.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index 070b843..8cff7ca 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -988,6 +988,7 @@ static int ghes_remove(struct platform_device *ghes_dev)
 		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);
-- 
2.8.0.rc2.1.gbe9624a