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authorSebastian Andrzej Siewior <bigeasy@linutronix.de>2021-08-19 22:30:30 +0300
committerThomas Gleixner <tglx@linutronix.de>2021-08-20 13:15:54 +0300
commitb857174e68e26f9c4f0796971e11eb63ad5a3eb6 (patch)
tree009dd241c14645e5ec8bc14d2ef6e8fa23b80dbb
parent9ae6ab27f44ee0da47520011afc04218f90e8b12 (diff)
downloadlinux-b857174e68e26f9c4f0796971e11eb63ad5a3eb6.tar.xz
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@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
-rw-r--r--kernel/locking/mutex.c2
1 files changed, 1 insertions, 1 deletions
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);