The following commit has been merged into the locking/core branch of tip: Commit-ID: b857174e68e26f9c4f0796971e11eb63ad5a3eb6 Gitweb: https://git.kernel.org/tip/b857174e68e26f9c4f0796971e11eb63ad5a3eb6 Author: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> AuthorDate: Thu, 19 Aug 2021 21:30:30 +02:00 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitterDate: Fri, 20 Aug 2021 12:15:54 +02:00 locking/ww_mutex: Initialize waiter.ww_ctx properly 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@xxxxxxxxxxxx> Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20210819193030.zpwrpvvrmy7xxxiy@xxxxxxxxxxxxx --- 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 3a65bf4..d456579 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);
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