linux-kernel - [PATCH 1/2] kasan: fix invalid-free test crashing the kernel

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Message-Id: <286eaefc0a6c3fa9b83b87e7d6dc0fbb5b5c9926.1519924383.git.andreyknvl@google.com>
Date:   Thu,  1 Mar 2018 18:15:42 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Nick Terrell <terrelln@...com>, Chris Mason <clm@...com>,
        Yury Norov <ynorov@...iumnetworks.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        "Luis R . Rodriguez" <mcgrof@...nel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Jeff Layton <jlayton@...hat.com>,
        "Jason A . Donenfeld" <Jason@...c4.com>,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-mm@...ck.org
Cc:     Kostya Serebryany <kcc@...gle.com>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH 1/2] kasan: fix invalid-free test crashing the kernel

When an invalid-free is triggered by one of the KASAN tests, the object
doesn't actually get freed. This later leads to a BUG failure in
kmem_cache_destroy that checks that there are no allocated objects in the
cache that is being destroyed. Fix this by calling kmem_cache_free with
the proper object address after the call that triggers invalid-free.

Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
---
 lib/test_kasan.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index 98854a64b014..ec657105edbf 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -567,7 +567,15 @@ static noinline void __init kmem_cache_invalid_free(void)
 		return;
 	}
 
+	/* Trigger invalid free, the object doesn't get freed */
 	kmem_cache_free(cache, p + 1);
+
+	/*
+	 * Properly free the object to prevent the "Objects remaining in
+	 * test_cache on __kmem_cache_shutdown" BUG failure.
+	 */
+	kmem_cache_free(cache, p);
+
 	kmem_cache_destroy(cache);
 }
 
-- 
2.16.2.395.g2e18187dfd-goog