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locking/ww_mutex: Initialize waiter.ww_ctx properly

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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: c0afb0ffc0 ("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
This commit is contained in:
Sebastian Andrzej Siewior 2021-08-19 21:30:30 +02:00 committed by Thomas Gleixner
parent 9ae6ab27f4
commit b857174e68
1 changed files with 1 additions and 1 deletions
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2
kernel/locking/mutex.c
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@ -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);