[PATCH] rcu: avoid alloc_pages() when recording stack

[Jun Miao]

The default kasan_record_aux_stack() calls stack_depot_save() with GFP_NOWAIT,
which in turn can then call alloc_pages(GFP_NOWAIT, ...).  In general, however,
it is not even possible to use either GFP_ATOMIC nor GFP_NOWAIT in certain
non-preemptive contexts/RT kernel including raw_spin_locks (see gfp.h and ab00db216c9c7).

Fix it by instructing stackdepot to not expand stack storage via alloc_pages()
in case it runs out by using kasan_record_aux_stack_noalloc().

Jianwei Hu reported:
 BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:969
 in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 15319, name: python3
 INFO: lockdep is turned off.
 irq event stamp: 0
 hardirqs last  enabled at (0): [<0000000000000000>] 0x0
 hardirqs last disabled at (0): [<ffffffff856c8b13>] copy_process+0xaf3/0x2590
 softirqs last  enabled at (0): [<ffffffff856c8b13>] copy_process+0xaf3/0x2590
 softirqs last disabled at (0): [<0000000000000000>] 0x0
 CPU: 6 PID: 15319 Comm: python3 Tainted: G        W  O 5.15-rc7-preempt-rt #1
 Hardware name: Supermicro SYS-E300-9A-8C/A2SDi-8C-HLN4F, BIOS 1.1b 12/17/2018
 Call Trace:
  show_stack+0x52/0x58
  dump_stack+0xa1/0xd6
  ___might_sleep.cold+0x11c/0x12d
  rt_spin_lock+0x3f/0xc0
  rmqueue+0x100/0x1460
  rmqueue+0x100/0x1460
  mark_usage+0x1a0/0x1a0
  ftrace_graph_ret_addr+0x2a/0xb0
  rmqueue_pcplist.constprop.0+0x6a0/0x6a0
   __kasan_check_read+0x11/0x20
   __zone_watermark_ok+0x114/0x270
   get_page_from_freelist+0x148/0x630
   is_module_text_address+0x32/0xa0
   __alloc_pages_nodemask+0x2f6/0x790
   __alloc_pages_slowpath.constprop.0+0x12d0/0x12d0
   create_prof_cpu_mask+0x30/0x30
   alloc_pages_current+0xb1/0x150
   stack_depot_save+0x39f/0x490
   kasan_save_stack+0x42/0x50
   kasan_save_stack+0x23/0x50
   kasan_record_aux_stack+0xa9/0xc0
   __call_rcu+0xff/0x9c0
   call_rcu+0xe/0x10
   put_object+0x53/0x70
   __delete_object+0x7b/0x90
   kmemleak_free+0x46/0x70
   slab_free_freelist_hook+0xb4/0x160
   kfree+0xe5/0x420
   kfree_const+0x17/0x30
   kobject_cleanup+0xaa/0x230
   kobject_put+0x76/0x90
   netdev_queue_update_kobjects+0x17d/0x1f0
   ... ...
   ksys_write+0xd9/0x180
   __x64_sys_write+0x42/0x50
   do_syscall_64+0x38/0x50
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fixes: 84109ab58590 ("rcu: Record kvfree_call_rcu() call stack for KASAN")
Fixes: 26e760c9a7c8 ("rcu: kasan: record and print call_rcu() call stack")
Reported-by: Jianwei Hu <jianwei.hu@xxxxxxxxxxxxx>
Signed-off-by: Jun Miao <jun.miao@xxxxxxxxxxxxx>
---
 kernel/rcu/tree.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 8270e58cd0f3..2c1034580f15 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3026,7 +3026,7 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func)
 	head->func = func;
 	head->next = NULL;
 	local_irq_save(flags);
-	kasan_record_aux_stack(head);
+	kasan_record_aux_stack_noalloc(head);
 	rdp = this_cpu_ptr(&rcu_data);
 
 	/* Add the callback to our list. */
@@ -3591,7 +3591,7 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
 		return;
 	}
 
-	kasan_record_aux_stack(ptr);
+	kasan_record_aux_stack_noalloc(ptr);
 	success = add_ptr_to_bulk_krc_lock(&krcp, &flags, ptr, !head);
 	if (!success) {
 		run_page_cache_worker(krcp);
-- 
2.33.0