linux-kernel - [PATCH RFC 08/10] kfence, lockdep: make KFENCE compatible with lockdep

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Message-Id: <20200907134055.2878499-9-elver@google.com>
Date:   Mon,  7 Sep 2020 15:40:53 +0200
From:   Marco Elver <elver@...gle.com>
To:     elver@...gle.com, glider@...gle.com, akpm@...ux-foundation.org,
        catalin.marinas@....com, cl@...ux.com, rientjes@...gle.com,
        iamjoonsoo.kim@....com, mark.rutland@....com, penberg@...nel.org
Cc:     hpa@...or.com, paulmck@...nel.org, andreyknvl@...gle.com,
        aryabinin@...tuozzo.com, luto@...nel.org, bp@...en8.de,
        dave.hansen@...ux.intel.com, dvyukov@...gle.com,
        edumazet@...gle.com, gregkh@...uxfoundation.org, mingo@...hat.com,
        jannh@...gle.com, corbet@....net, keescook@...omium.org,
        peterz@...radead.org, cai@....pw, tglx@...utronix.de,
        will@...nel.org, x86@...nel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org
Subject: [PATCH RFC 08/10] kfence, lockdep: make KFENCE compatible with lockdep

Lockdep checks that dynamic key registration is only performed on keys
that are not static objects. With KFENCE, it is possible that such a
dynamically allocated key is a KFENCE object which may, however, be
allocated from a static memory pool (if HAVE_ARCH_KFENCE_STATIC_POOL).

Therefore, ignore KFENCE-allocated objects in static_obj().

Co-developed-by: Alexander Potapenko <glider@...gle.com>
Signed-off-by: Alexander Potapenko <glider@...gle.com>
Signed-off-by: Marco Elver <elver@...gle.com>
---
 kernel/locking/lockdep.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 54b74fabf40c..0cf5d5ecbd31 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -38,6 +38,7 @@
 #include <linux/seq_file.h>
 #include <linux/spinlock.h>
 #include <linux/kallsyms.h>
+#include <linux/kfence.h>
 #include <linux/interrupt.h>
 #include <linux/stacktrace.h>
 #include <linux/debug_locks.h>
@@ -755,6 +756,13 @@ static int static_obj(const void *obj)
 	if (arch_is_kernel_initmem_freed(addr))
 		return 0;
 
+	/*
+	 * KFENCE objects may be allocated from a static memory pool, but are
+	 * not actually static objects.
+	 */
+	if (is_kfence_address(obj))
+		return 0;
+
 	/*
 	 * static variable?
 	 */
-- 
2.28.0.526.ge36021eeef-goog