The patch titled Subject: kasan: make kasan_record_aux_stack_noalloc() the default behaviour has been added to the -mm mm-unstable branch. Its filename is kasan-make-kasan_record_aux_stack_noalloc-the-default-behaviour.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kasan-make-kasan_record_aux_stack_noalloc-the-default-behaviour.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Subject: kasan: make kasan_record_aux_stack_noalloc() the default behaviour Date: Fri, 22 Nov 2024 16:54:51 +0100 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@xxxxxxxxxxxxxx/ | 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@xxxxxxxxxxxxx: dressed the diff as patch] Link: https://lkml.kernel.org/r/20241122155451.Mb2pmeyJ@xxxxxxxxxxxxx Fixes: 7cb3007ce2da2 ("kasan: generic: introduce kasan_record_aux_stack_noalloc()") Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Reported-by: syzbot+39f85d612b7c20d8db48@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://lore.kernel.org/all/67275485.050a0220.3c8d68.0a37.GAE@googl= e.com Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx> Reviewed-by: Marco Elver <elver@xxxxxxxxxx> Reviewed-by: Waiman Long <longman@xxxxxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx> Cc: Ben Segall <bsegall@xxxxxxxxxx> Cc: Boqun Feng <boqun.feng@xxxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Frederic Weisbecker <frederic@xxxxxxxxxx> Cc: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Jann Horn <jannh@xxxxxxxxxx> Cc: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx> Cc: Juri Lelli <juri.lelli@xxxxxxxxxx> Cc: <kasan-dev@xxxxxxxxxxxxxxxx> Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx> Cc: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> Cc: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx> Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxx> Cc: Neeraj Upadhyay <neeraj.upadhyay@xxxxxxxxxx> Cc: Paul E. McKenney <paulmck@xxxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> Cc: syzkaller-bugs@xxxxxxxxxxxxxxxx Cc: Tejun Heo <tj@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx> Cc: Valentin Schneider <vschneid@xxxxxxxxxx> Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx> Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Zqiang <qiang.zhang1211@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/kasan.h | 2 -- include/linux/task_work.h | 3 --- kernel/irq_work.c | 2 +- kernel/rcu/tiny.c | 2 +- kernel/rcu/tree.c | 4 ++-- kernel/sched/core.c | 2 +- kernel/task_work.c | 14 +------------- kernel/workqueue.c | 2 +- mm/kasan/generic.c | 18 ++++++------------ mm/slub.c | 2 +- 10 files changed, 14 insertions(+), 37 deletions(-) --- a/include/linux/kasan.h~kasan-make-kasan_record_aux_stack_noalloc-the-default-behaviour +++ a/include/linux/kasan.h @@ -491,7 +491,6 @@ void kasan_cache_create(struct kmem_cach void kasan_cache_shrink(struct kmem_cache *cache); void kasan_cache_shutdown(struct kmem_cache *cache); void kasan_record_aux_stack(void *ptr); -void kasan_record_aux_stack_noalloc(void *ptr); #else /* CONFIG_KASAN_GENERIC */ @@ -509,7 +508,6 @@ static inline void kasan_cache_create(st static inline void kasan_cache_shrink(struct kmem_cache *cache) {} static inline void kasan_cache_shutdown(struct kmem_cache *cache) {} static inline void kasan_record_aux_stack(void *ptr) {} -static inline void kasan_record_aux_stack_noalloc(void *ptr) {} #endif /* CONFIG_KASAN_GENERIC */ --- a/include/linux/task_work.h~kasan-make-kasan_record_aux_stack_noalloc-the-default-behaviour +++ a/include/linux/task_work.h @@ -19,9 +19,6 @@ enum task_work_notify_mode { TWA_SIGNAL, TWA_SIGNAL_NO_IPI, TWA_NMI_CURRENT, - - TWA_FLAGS = 0xff00, - TWAF_NO_ALLOC = 0x0100, }; static inline bool task_work_pending(struct task_struct *task) --- a/kernel/irq_work.c~kasan-make-kasan_record_aux_stack_noalloc-the-default-behaviour +++ a/kernel/irq_work.c @@ -147,7 +147,7 @@ bool irq_work_queue_on(struct irq_work * if (!irq_work_claim(work)) return false; - kasan_record_aux_stack_noalloc(work); + kasan_record_aux_stack(work); preempt_disable(); if (cpu != smp_processor_id()) { --- a/kernel/rcu/tiny.c~kasan-make-kasan_record_aux_stack_noalloc-the-default-behaviour +++ a/kernel/rcu/tiny.c @@ -250,7 +250,7 @@ EXPORT_SYMBOL_GPL(poll_state_synchronize void kvfree_call_rcu(struct rcu_head *head, void *ptr) { if (head) - kasan_record_aux_stack_noalloc(ptr); + kasan_record_aux_stack(ptr); __kvfree_call_rcu(head, ptr); } --- a/kernel/rcu/tree.c~kasan-make-kasan_record_aux_stack_noalloc-the-default-behaviour +++ a/kernel/rcu/tree.c @@ -3083,7 +3083,7 @@ __call_rcu_common(struct rcu_head *head, } head->func = func; head->next = NULL; - kasan_record_aux_stack_noalloc(head); + kasan_record_aux_stack(head); local_irq_save(flags); rdp = this_cpu_ptr(&rcu_data); lazy = lazy_in && !rcu_async_should_hurry(); @@ -3817,7 +3817,7 @@ void kvfree_call_rcu(struct rcu_head *he return; } - kasan_record_aux_stack_noalloc(ptr); + kasan_record_aux_stack(ptr); success = add_ptr_to_bulk_krc_lock(&krcp, &flags, ptr, !head); if (!success) { run_page_cache_worker(krcp); --- a/kernel/sched/core.c~kasan-make-kasan_record_aux_stack_noalloc-the-default-behaviour +++ a/kernel/sched/core.c @@ -10590,7 +10590,7 @@ void task_tick_mm_cid(struct rq *rq, str return; /* No page allocation under rq lock */ - task_work_add(curr, work, TWA_RESUME | TWAF_NO_ALLOC); + task_work_add(curr, work, TWA_RESUME); } void sched_mm_cid_exit_signals(struct task_struct *t) --- a/kernel/task_work.c~kasan-make-kasan_record_aux_stack_noalloc-the-default-behaviour +++ a/kernel/task_work.c @@ -55,26 +55,14 @@ int task_work_add(struct task_struct *ta 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); --- a/kernel/workqueue.c~kasan-make-kasan_record_aux_stack_noalloc-the-default-behaviour +++ a/kernel/workqueue.c @@ -2180,7 +2180,7 @@ static void insert_work(struct pool_work debug_work_activate(work); /* record the work call stack in order to print it in KASAN reports */ - kasan_record_aux_stack_noalloc(work); + kasan_record_aux_stack(work); /* we own @work, set data and link */ set_work_pwq(work, pwq, extra_flags); --- a/mm/kasan/generic.c~kasan-make-kasan_record_aux_stack_noalloc-the-default-behaviour +++ a/mm/kasan/generic.c @@ -524,7 +524,11 @@ size_t kasan_metadata_size(struct kmem_c sizeof(struct kasan_free_meta) : 0); } -static void __kasan_record_aux_stack(void *addr, depot_flags_t depot_flags) +/* + * This function avoids dynamic memory allocations and thus can be called from + * contexts that do not allow allocating memory. + */ +void kasan_record_aux_stack(void *addr) { struct slab *slab = kasan_addr_to_slab(addr); struct kmem_cache *cache; @@ -541,17 +545,7 @@ static void __kasan_record_aux_stack(voi return; alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0]; - alloc_meta->aux_stack[0] = kasan_save_stack(0, depot_flags); -} - -void kasan_record_aux_stack(void *addr) -{ - return __kasan_record_aux_stack(addr, STACK_DEPOT_FLAG_CAN_ALLOC); -} - -void kasan_record_aux_stack_noalloc(void *addr) -{ - return __kasan_record_aux_stack(addr, 0); + alloc_meta->aux_stack[0] = kasan_save_stack(0, 0); } void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags) --- a/mm/slub.c~kasan-make-kasan_record_aux_stack_noalloc-the-default-behaviour +++ a/mm/slub.c @@ -2296,7 +2296,7 @@ bool slab_free_hook(struct kmem_cache *s * We have to do this manually because the rcu_head is * not located inside the object. */ - kasan_record_aux_stack_noalloc(x); + kasan_record_aux_stack(x); delayed_free->object = x; call_rcu(&delayed_free->head, slab_free_after_rcu_debug); _ Patches currently in -mm which might be from peterz@xxxxxxxxxxxxx are kasan-make-kasan_record_aux_stack_noalloc-the-default-behaviour.patch