[PATCH v2] workqueue: Don't record workqueue stack holding raw_spin_lock

* [PATCH v2] workqueue: Don't record workqueue stack holding raw_spin_lock
@ 2021-09-02 20:01 Shuah Khan
  2021-09-02 21:58 ` Marco Elver
  0 siblings, 1 reply; 5+ messages in thread
From: Shuah Khan @ 2021-09-02 20:01 UTC (permalink / raw)
  To: tj, jiangshanlai, akpm, elver, andreyknvl, dvyukov, walter-zh.wu
  Cc: Shuah Khan, linux-kernel

When CONFIG_PROVE_RAW_LOCK_NESTING=y and CONFIG_KASAN are enabled,
kasan_record_aux_stack() runs into "BUG: Invalid wait context" when
it tries to allocate memory attempting to acquire spinlock in page
allocation code while holding workqueue pool raw_spinlock.

There are several instances of this problem when block layer tries
to __queue_work(). Call trace from one of these instances is below:

    kblockd_mod_delayed_work_on()
      mod_delayed_work_on()
        __queue_delayed_work()
          __queue_work() (rcu_read_lock, raw_spin_lock pool->lock held)
            insert_work()
	      kasan_record_aux_stack()
                kasan_save_stack()
		  stack_depot_save()
                    alloc_pages()
                      __alloc_pages()
                        get_page_from_freelist()
                          rm_queue()
                            rm_queue_pcplist()
                              local_lock_irqsave(&pagesets.lock, flags);
                              [ BUG: Invalid wait context triggered ]

Fix it by calling kasan_record_aux_stack() conditionally only when
CONFIG_PROVE_RAW_LOCK_NESTING is not enabled. After exploring other
options such as calling kasan_record_aux_stack() after releasing the
pool lock, opting for a least disruptive path of stubbing this record
function to avoid nesting raw spinlock and spinlock.

=============================
 [ BUG: Invalid wait context ]
 5.14.0-rc7+ #8 Not tainted
 -----------------------------
 snap/532 is trying to lock:
 ffff888374f32ba0 (lock#2){..-.}-{3:3}, at: get_page_from_freelist (mm/page_alloc.c:3665 mm/page_alloc.c:3703 mm/page_alloc.c:4165)
 other info that might help us debug this:
 context-{5:5}
 3 locks held by snap/532:
 #0: ffff888139fa4408 (&type->i_mutex_dir_key#10){.+.+}-{4:4}, at: walk_component (fs/namei.c:1663 fs/namei.c:1959)
 #1: ffffffffab870c40 (rcu_read_lock){....}-{1:3}, at: __queue_work (./arch/x86/include/asm/preempt.h:80 ./include/linux/rcupdate.h:68 ./include/linux/rcupdate.h:685 kernel/workqueue.c:1421)
 #2: ffff888374f36cd8 (&pool->lock){-.-.}-{2:2}, at: __queue_work (kernel/workqueue.c:1466)
 stack backtrace:
 CPU: 14 PID: 532 Comm: snap Not tainted 5.14.0-rc7+ #8
 Hardware name: LENOVO 90Q30008US/3728, BIOS O4ZKT1CA 09/16/2020
 Call Trace:
 dump_stack_lvl (lib/dump_stack.c:106 (discriminator 4))
 dump_stack (lib/dump_stack.c:113)
 __lock_acquire.cold (kernel/locking/lockdep.c:4666 kernel/locking/lockdep.c:4727 kernel/locking/lockdep.c:4965)
 ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4873)
 ? lock_is_held_type (kernel/locking/lockdep.c:5368 kernel/locking/lockdep.c:5668)
 lock_acquire (kernel/locking/lockdep.c:438 kernel/locking/lockdep.c:5627 kernel/locking/lockdep.c:5590)
 ? get_page_from_freelist (mm/page_alloc.c:3665 mm/page_alloc.c:3703 mm/page_alloc.c:4165)
 ? lock_release (kernel/locking/lockdep.c:5593)
 ? __kasan_check_read (mm/kasan/shadow.c:32)
 ? __lock_acquire (kernel/locking/lockdep.c:5019)
 ? __zone_watermark_ok (./include/linux/list.h:282 ./include/linux/mmzone.h:111 mm/page_alloc.c:3908)
 get_page_from_freelist (./include/linux/local_lock_internal.h:43 mm/page_alloc.c:3665 mm/page_alloc.c:3703 mm/page_alloc.c:4165)
 ? get_page_from_freelist (mm/page_alloc.c:3665 mm/page_alloc.c:3703 mm/page_alloc.c:4165)
 ? lock_is_held_type (kernel/locking/lockdep.c:5368 kernel/locking/lockdep.c:5668)
 ? is_bpf_text_address (./arch/x86/include/asm/preempt.h:85 ./include/linux/rcupdate.h:73 ./include/linux/rcupdate.h:719 kernel/bpf/core.c:708)
 ? lock_downgrade (kernel/locking/lockdep.c:5633)
 ? __zone_watermark_ok (mm/page_alloc.c:4054)
 __alloc_pages (mm/page_alloc.c:5391)
 ? __alloc_pages_slowpath.constprop.0 (mm/page_alloc.c:5354)
 ? create_prof_cpu_mask (kernel/stacktrace.c:82)
? _find_first_bit (lib/find_bit.c:83)
 alloc_pages (mm/mempolicy.c:2249)
 stack_depot_save (lib/stackdepot.c:304)
 ? lock_is_held_type (kernel/locking/lockdep.c:5368 kernel/locking/lockdep.c:5668)
 kasan_save_stack (mm/kasan/common.c:41)
 ? kasan_save_stack (mm/kasan/common.c:39)
 ? kasan_record_aux_stack (mm/kasan/generic.c:348)
 ? insert_work (./include/linux/instrumented.h:71 ./include/asm-generic/bitops/instrumented-non-atomic.h:134 kernel/workqueue.c:616 kernel/workqueue.c:623 kernel/workqueue.c:1335)
 ? __queue_work (kernel/workqueue.c:1501)
 ? __queue_delayed_work (kernel/workqueue.c:1657)
 ? mod_delayed_work_on (kernel/workqueue.c:1720)
 ? kblockd_mod_delayed_work_on (block/blk-core.c:1633)
 ? __blk_mq_delay_run_hw_queue (block/blk-mq.c:1567)
 ? blk_mq_run_hw_queue (block/blk-mq.c:1610)
 ? blk_mq_sched_insert_request (block/blk-mq-sched.c:480)
 ? blk_mq_submit_bio (block/blk-mq.c:2276)

Fixes: e89a85d63fb2 ("workqueue: kasan: record workqueue stack")
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
Changes since v1:
-- Instead of changing when record happens, disable record
   when CONFIG_PROVE_RAW_LOCK_NESTING=y
 
 kernel/workqueue.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index f148eacda55a..435970ef81ae 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1328,8 +1328,16 @@ static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
 {
 	struct worker_pool *pool = pwq->pool;
 
-	/* record the work call stack in order to print it in KASAN reports */
+	/*
+	 * record the work call stack in order to print it in KASAN reports
+	 * Doing this when CONFIG_PROVE_RAW_LOCK_NESTING is enabled results
+	 * in nesting raw spinlock with page allocation spinlock.
+	 *
+	 * Avoid recording when CONFIG_PROVE_RAW_LOCK_NESTING is enabled.
+	 */
+#if !defined(CONFIG_PROVE_RAW_LOCK_NESTING)
 	kasan_record_aux_stack(work);
+#endif
 
 	/* we own @work, set data and link */
 	set_work_pwq(work, pwq, extra_flags);
-- 
2.30.2


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