linux-kernel - [PATCH 4.19 03/92] PCI: hotplug: ACPI: Fix context refcounting in acpiphp_grab

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Date:   Thu, 20 Aug 2020 11:20:48 +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, Vasily Averin <vvs@...tuozzo.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: [PATCH 4.19 03/92] PCI: hotplug: ACPI: Fix context refcounting in acpiphp_grab_context()

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

commit dae68d7fd4930315389117e9da35b763f12238f9 upstream.

If context is not NULL in acpiphp_grab_context(), but the
is_going_away flag is set for the device's parent, the reference
counter of the context needs to be decremented before returning
NULL or the context will never be freed, so make that happen.

Fixes: edf5bf34d408 ("ACPI / dock: Use callback pointers from devices' ACPI hotplug contexts")
Reported-by: Vasily Averin <vvs@...tuozzo.com>
Cc: 3.15+ <stable@...r.kernel.org> # 3.15+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/pci/hotplug/acpiphp_glue.c |   14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

--- a/drivers/pci/hotplug/acpiphp_glue.c
+++ b/drivers/pci/hotplug/acpiphp_glue.c
@@ -122,13 +122,21 @@ static struct acpiphp_context *acpiphp_g
 	struct acpiphp_context *context;

 	acpi_lock_hp_context();
+
 	context = acpiphp_get_context(adev);
-	if (!context || context->func.parent->is_going_away) {
-		acpi_unlock_hp_context();
-		return NULL;
+	if (!context)
+		goto unlock;
+
+	if (context->func.parent->is_going_away) {
+		acpiphp_put_context(context);
+		context = NULL;
+		goto unlock;
 	}
+
 	get_bridge(context->func.parent);
 	acpiphp_put_context(context);
+
+unlock:
 	acpi_unlock_hp_context();
 	return context;
 }