kasan: make kasan_record_aux_stack_noalloc() the default behaviour

kasan_record_aux_stack_noalloc() was introduced to record a stack trace
without allocating memory in the process.  It has been added to callers
which were invoked while a raw_spinlock_t was held.  More and more callers
were identified and changed over time.  Is it a good thing to have this
while functions try their best to do a locklessly setup?  The only
downside of having kasan_record_aux_stack() not allocate any memory is
that we end up without a stacktrace if stackdepot runs out of memory and
at the same stacktrace was not recorded before To quote Marco Elver from
https://lore.kernel.org/all/CANpmjNPmQYJ7pv1N3cuU8cP18u7PP_uoZD8YxwZd4jtbof9nVQ@mail.gmail.com/

| I'd be in favor, it simplifies things. And stack depot should be
| able to replenish its pool sufficiently in the "non-aux" cases
| i.e. regular allocations. Worst case we fail to record some
| aux stacks, but I think that's only really bad if there's a bug
| around one of these allocations. In general the probabilities
| of this being a regression are extremely small [...]

Make the kasan_record_aux_stack_noalloc() behaviour default as
kasan_record_aux_stack().

[bigeasy@linutronix.de: dressed the diff as patch]
Link: https://lkml.kernel.org/r/20241122155451.Mb2pmeyJ@linutronix.de
Fixes: 7cb3007ce2da ("kasan: generic: introduce kasan_record_aux_stack_noalloc()")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reported-by: syzbot+39f85d612b7c20d8db48@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/67275485.050a0220.3c8d68.0a37.GAE@google.com
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Ben Segall <bsegall@google.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: <kasan-dev@googlegroups.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: syzkaller-bugs@googlegroups.com
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zqiang <qiang.zhang1211@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 1 insertions, 13 deletions

diff --git a/kernel/task_work.c b/kernel/task_work.c
index c969f1f26be5..d1efec571a4a 100644
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -55,26 +55,14 @@ int task_work_add(struct task_struct *task, struct callback_head *work,
 		  enum task_work_notify_mode notify)
 {
 	struct callback_head *head;
-	int flags = notify & TWA_FLAGS;
 
-	notify &= ~TWA_FLAGS;
 	if (notify == TWA_NMI_CURRENT) {
 		if (WARN_ON_ONCE(task != current))
 			return -EINVAL;
 		if (!IS_ENABLED(CONFIG_IRQ_WORK))
 			return -EINVAL;
 	} else {
-		/*
-		 * Record the work call stack in order to print it in KASAN
-		 * reports.
-		 *
-		 * Note that stack allocation can fail if TWAF_NO_ALLOC flag
-		 * is set and new page is needed to expand the stack buffer.
-		 */
-		if (flags & TWAF_NO_ALLOC)
-			kasan_record_aux_stack_noalloc(work);
-		else
-			kasan_record_aux_stack(work);
+		kasan_record_aux_stack(work);
 	}
 
 	head = READ_ONCE(task->task_works);