linux-kernel - [PATCH -next] lib: fix test

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Date:   Wed, 17 Jun 2020 22:31:21 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>
Cc:     Jérôme Glisse <jglisse@...hat.com>,
        Ralph Campbell <rcampbell@...dia.com>
Subject: [PATCH -next] lib: fix test_hmm.c reference after free

From: Randy Dunlap <rdunlap@...radead.org>

Coccinelle scripts report the following errors:

lib/test_hmm.c:523:20-26: ERROR: reference preceded by free on line 521
lib/test_hmm.c:524:21-27: ERROR: reference preceded by free on line 521
lib/test_hmm.c:523:28-35: ERROR: devmem is NULL but dereferenced.
lib/test_hmm.c:524:29-36: ERROR: devmem is NULL but dereferenced.

Fix these by using the local variable 'res' instead of devmem.

Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
Cc: Jérôme Glisse <jglisse@...hat.com>
Cc: linux-mm@...ck.org
Cc: Ralph Campbell <rcampbell@...dia.com>
---
 lib/test_hmm.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- linux-next-20200617.orig/lib/test_hmm.c
+++ linux-next-20200617/lib/test_hmm.c
@@ -520,8 +520,7 @@ static bool dmirror_allocate_chunk(struc
 err_free:
 	kfree(devmem);
 err_release:
-	release_mem_region(devmem->pagemap.res.start,
-			   resource_size(&devmem->pagemap.res));
+	release_mem_region(res->start, resource_size(res));
 err:
 	mutex_unlock(&mdevice->devmem_lock);
 	return false;