linux-kernel - [PATCH 1/2] lockdep: allow instrumenting lockdep.c with KMSAN

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Message-ID: <20221128094541.2645890-1-glider@google.com>
Date:   Mon, 28 Nov 2022 10:45:40 +0100
From:   Alexander Potapenko <glider@...gle.com>
To:     glider@...gle.com
Cc:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        peterz@...radead.org, mingo@...hat.com, will@...nel.org,
        elver@...gle.com, dvyukov@...gle.com, linux-mm@...ck.org,
        kasan-dev@...glegroups.com, Eric Biggers <ebiggers@...nel.org>
Subject: [PATCH 1/2] lockdep: allow instrumenting lockdep.c with KMSAN

Lockdep and KMSAN used to play badly together, causing deadlocks when
KMSAN instrumentation of lockdep.c called lockdep functions recursively.

Looks like this is no more the case, and a kernel can run (yet slower)
with both KMSAN and lockdep enabled.
This patch should fix false positives on wq_head->lock->dep_map, which
KMSAN used to consider uninitialized because of lockdep.c not being
instrumented.

Link: https://lore.kernel.org/lkml/Y3b9AAEKp2Vr3e6O@sol.localdomain/
Reported-by: Eric Biggers <ebiggers@...nel.org>
Signed-off-by: Alexander Potapenko <glider@...gle.com>
---
 kernel/locking/Makefile | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/locking/Makefile b/kernel/locking/Makefile
index ea925731fa40f..0db4093d17b8a 100644
--- a/kernel/locking/Makefile
+++ b/kernel/locking/Makefile
@@ -7,7 +7,6 @@ obj-y += mutex.o semaphore.o rwsem.o percpu-rwsem.o
 
 # Avoid recursion lockdep -> sanitizer -> ... -> lockdep.
 KCSAN_SANITIZE_lockdep.o := n
-KMSAN_SANITIZE_lockdep.o := n
 
 ifdef CONFIG_FUNCTION_TRACER
 CFLAGS_REMOVE_lockdep.o = $(CC_FLAGS_FTRACE)
-- 
2.38.1.584.g0f3c55d4c2-goog