[PATCH] kernel/resource: Fix return code check in __request_free_mem_region

From: Alistair Popple <apopple@nvidia.com>
To: <akpm@linux-foundation.org>
Cc: <bsingharora@gmail.com>, <dan.j.williams@intel.com>,
	<daniel.vetter@ffwll.ch>, <david@redhat.com>,
	<gregkh@linuxfoundation.org>, <jglisse@redhat.com>,
	<jhubbard@nvidia.com>, <linux-mm@kvack.org>, <smuchun@gmail.com>,
	<linux-kernel@vger.kernel.org>,
	Alistair Popple <apopple@nvidia.com>,
	kernel test robot <oliver.sang@intel.com>
Subject: [PATCH] kernel/resource: Fix return code check in __request_free_mem_region
Date: Wed, 12 May 2021 17:35:28 +1000	[thread overview]
Message-ID: <20210512073528.22334-1-apopple@nvidia.com> (raw)

Splitting an earlier version of a patch that allowed calling
__request_region() while holding the resource lock into a series of
patches required changing the return code for the newly introduced
__request_region_locked().

Unfortunately this change was not carried through to a subsequent
commit 56fd94919b8b ("kernel/resource: fix locking in
request_free_mem_region") in the series. This resulted in a
use-after-free due to freeing the struct resource without properly
releasing it. Fix this by correcting the return code check so that the
struct is not freed if the request to add it was successful.

Reported-by: kernel test robot <oliver.sang@intel.com>
Fixes: 56fd94919b8b ("kernel/resource: fix locking in request_free_mem_region")
Signed-off-by: Alistair Popple <apopple@nvidia.com>
---
 kernel/resource.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index 028a5ab18818..ca9f5198a01f 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1805,7 +1805,7 @@ static struct resource *__request_free_mem_region(struct device *dev,
 				REGION_DISJOINT)
 			continue;
 
-		if (!__request_region_locked(res, &iomem_resource, addr, size,
+		if (__request_region_locked(res, &iomem_resource, addr, size,
 						name, 0))
 			break;
 
-- 
2.20.1

