From b857174e68e26f9c4f0796971e11eb63ad5a3eb6 Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 19 Aug 2021 21:30:30 +0200
Subject: [PATCH] locking/ww_mutex: Initialize waiter.ww_ctx properly
Git-commit: b857174e68e26f9c4f0796971e11eb63ad5a3eb6
Patch-mainline: v5.15-rc1
References: bsc#1190137 bsc#1189998
The consolidation of the debug code for mutex waiter intialization sets
waiter::ww_ctx to a poison value unconditionally. For regular mutexes this
is intended to catch the case where waiter_ww_ctx is dereferenced
accidentally.
For ww_mutex the poison value has to be overwritten either with a context
pointer or NULL for ww_mutexes without context.
The rework broke this as it made the store conditional on the context
pointer instead of the argument which signals whether ww_mutex code should
be compiled in or optiized out. As a result waiter::ww_ctx ends up with the
poison pointer for contextless ww_mutexes which causes a later dereference of
the poison pointer because it is != NULL.
Use the build argument instead so for ww_mutex the poison value is always
overwritten.
Fixes: c0afb0ffc06e6 ("locking/ww_mutex: Gather mutex_waiter initialization")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210819193030.zpwrpvvrmy7xxxiy@linutronix.de
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
kernel/locking/mutex.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 3a65bf4bacfd..d456579d0952 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -618,7 +618,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
debug_mutex_lock_common(lock, &waiter);
waiter.task = current;
- if (ww_ctx)
+ if (use_ww_ctx)
waiter.ww_ctx = ww_ctx;
lock_contended(&lock->dep_map, ip);
--
2.26.2