Peter Zijlstra 8b405d5c5d locking/lockdep: Fix stacktrace mess ... There is some complication between check_prevs_add() and check_prev_add() wrt. saving stack traces. The problem is that we want to be frugal with saving stack traces, since it consumes static resources. We'll only know in check_prev_add() if we need the trace, but we can call into it multiple times. So we want to do on-demand and re-use. A further complication is that check_prev_add() can drop graph_lock and mess with our static resources. In any case, the current state; after commit: ce07a9415f ("locking/lockdep: Make check_prev_add() able to handle external stack_trace") is that we'll assume the trace contains valid data once check_prev_add() returns '2'. However, as noted by Josh, this is false, check_prev_add() can return '2' before having saved a trace, this then result in the possibility of using uninitialized data. Testing, as reported by Wu, shows a NULL deref. So simplify. Since the graph_lock() thing is a debug path that hasn't really been used in a long while, take it out back and avoid the head-ache. Further initialize the stack_trace to a known 'empty' state; as long as nr_entries == 0, nothing should deref entries. We can then use the 'entries == NULL' test for a valid trace / on-demand saving. Analyzed-by: Josh Poimboeuf <jpoimboe@redhat.com> Reported-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Byungchul Park <byungchul.park@lge.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: ce07a9415f ("locking/lockdep: Make check_prev_add() able to handle external stack_trace") Signed-off-by: Ingo Molnar <mingo@kernel.org>		2017-10-10 10:04:28 +02:00
..
lockdep_internals.h	locking/lockdep: Avoid creating redundant links	2017-08-10 12:29:04 +02:00
lockdep_proc.c	locking/lockdep: Avoid creating redundant links	2017-08-10 12:29:04 +02:00
lockdep_states.h	locking/lockdep: Rework FS_RECLAIM annotation	2017-08-10 12:29:03 +02:00
lockdep.c	locking/lockdep: Fix stacktrace mess	2017-10-10 10:04:28 +02:00
locktorture.c
Makefile
mcs_spinlock.h
mutex-debug.c
mutex-debug.h
mutex.c	mutex, futex: adjust kernel-doc markups to generate ReST	2017-05-16 08:43:25 -03:00
mutex.h
osq_lock.c	locking/osq_lock: Fix osq_lock queue corruption	2017-08-10 12:28:54 +02:00
percpu-rwsem.c
qrwlock.c	kernel/locking: Fix compile error with qrwlock.c	2017-05-25 12:06:50 -07:00
qspinlock_paravirt.h	locking/pvqspinlock: Relax cmpxchg's to improve performance on some architectures	2017-08-29 15:14:38 +02:00
qspinlock_stat.h
qspinlock.c	locking: Remove spin_unlock_wait() generic definitions	2017-08-17 08:08:58 -07:00
rtmutex_common.h	locking/rtmutex: replace top-waiter and pi_waiters leftmost caching	2017-09-08 18:26:49 -07:00
rtmutex-debug.c	locking/rtmutex: replace top-waiter and pi_waiters leftmost caching	2017-09-08 18:26:49 -07:00
rtmutex-debug.h	rt_mutex: Add lockdep annotations	2017-06-08 10:35:49 +02:00
rtmutex.c	locking/rtmutex: replace top-waiter and pi_waiters leftmost caching	2017-09-08 18:26:49 -07:00
rtmutex.h	rt_mutex: Add lockdep annotations	2017-06-08 10:35:49 +02:00
rwsem-spinlock.c	locking/rwsem-spinlock: Add killable versions of __down_read()	2017-08-10 12:28:55 +02:00
rwsem-xadd.c	locking/rwsem-xadd: Fix missed wakeup due to reordering of load	2017-09-29 10:10:20 +02:00
rwsem.c
rwsem.h
semaphore.c
spinlock_debug.c
spinlock.c
test-ww_mutex.c	mm: treewide: remove GFP_TEMPORARY allocation flag	2017-09-13 18:53:16 -07:00