Re: BUG: sleeping function called from invalid context in __alloc_pages_nodemask

[Tetsuo Handa]

On 2019/11/30 17:32, Hillf Danton wrote:
> 
> On Fri, 29 Nov 2019 23:35:08 -0800
>> Hello,
>>
>> syzbot found the following crash on:
>>
>> HEAD commit:    419593da Add linux-next specific files for 20191129
>> git tree:       linux-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=12cc369ce00000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=7c04b0959e75c206
>> dashboard link: https://syzkaller.appspot.com/bug?extid=4925d60532bf4c399608
>> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
>>
>> Unfortunately, I don't have any reproducer for this crash yet.
>>
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+4925d60532bf4c399608@xxxxxxxxxxxxxxxxxxxxxxxxx
>>
>> BUG: sleeping function called from invalid context at mm/page_alloc.c:4681
>> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 2710, name:  
>> kworker/0:2
>> 4 locks held by kworker/0:2/2710:
>>   #0: ffff8880aa026d28 ((wq_completion)events){+.+.}, at: __write_once_size  
>> include/linux/compiler.h:247 [inline]
>>   #0: ffff8880aa026d28 ((wq_completion)events){+.+.}, at: arch_atomic64_set  
>> arch/x86/include/asm/atomic64_64.h:34 [inline]
>>   #0: ffff8880aa026d28 ((wq_completion)events){+.+.}, at: atomic64_set  
>> include/asm-generic/atomic-instrumented.h:868 [inline]
>>   #0: ffff8880aa026d28 ((wq_completion)events){+.+.}, at: atomic_long_set  
>> include/asm-generic/atomic-long.h:40 [inline]
>>   #0: ffff8880aa026d28 ((wq_completion)events){+.+.}, at: set_work_data  
>> kernel/workqueue.c:615 [inline]
>>   #0: ffff8880aa026d28 ((wq_completion)events){+.+.}, at:  
>> set_work_pool_and_clear_pending kernel/workqueue.c:642 [inline]
>>   #0: ffff8880aa026d28 ((wq_completion)events){+.+.}, at:  
>> process_one_work+0x88b/0x1740 kernel/workqueue.c:2235
>>   #1: ffffc9000802fdc0 (pcpu_balance_work){+.+.}, at:  
>> process_one_work+0x8c1/0x1740 kernel/workqueue.c:2239
>>   #2: ffffffff8983ff20 (pcpu_alloc_mutex){+.+.}, at:  
>> pcpu_balance_workfn+0xb7/0x1310 mm/percpu.c:1845
>>   #3: ffffffff89851b18 (vmap_area_lock){+.+.}, at: spin_lock  
>> include/linux/spinlock.h:338 [inline]
>>   #3: ffffffff89851b18 (vmap_area_lock){+.+.}, at:  
>> pcpu_get_vm_areas+0x3b27/0x3f00 mm/vmalloc.c:3431
>> Preemption disabled at:
>> [<ffffffff81a89ce7>] spin_lock include/linux/spinlock.h:338 [inline]
>> [<ffffffff81a89ce7>] pcpu_get_vm_areas+0x3b27/0x3f00 mm/vmalloc.c:3431
>> CPU: 0 PID: 2710 Comm: kworker/0:2 Not tainted  
>> 5.4.0-next-20191129-syzkaller #0
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
>> Google 01/01/2011
>> Workqueue: events pcpu_balance_workfn
>> Call Trace:
>>   __dump_stack lib/dump_stack.c:77 [inline]
>>   dump_stack+0x197/0x210 lib/dump_stack.c:118
>>   ___might_sleep.cold+0x1fb/0x23e kernel/sched/core.c:6800
>>   __might_sleep+0x95/0x190 kernel/sched/core.c:6753
>>   prepare_alloc_pages mm/page_alloc.c:4681 [inline]
>>   __alloc_pages_nodemask+0x523/0x910 mm/page_alloc.c:4730
>>   alloc_pages_current+0x107/0x210 mm/mempolicy.c:2211
>>   alloc_pages include/linux/gfp.h:532 [inline]
>>   __get_free_pages+0xc/0x40 mm/page_alloc.c:4786
>>   kasan_populate_vmalloc_pte mm/kasan/common.c:762 [inline]
>>   kasan_populate_vmalloc_pte+0x2f/0x1c0 mm/kasan/common.c:753
>>   apply_to_pte_range mm/memory.c:2041 [inline]
>>   apply_to_pmd_range mm/memory.c:2068 [inline]
>>   apply_to_pud_range mm/memory.c:2088 [inline]
>>   apply_to_p4d_range mm/memory.c:2108 [inline]
>>   apply_to_page_range+0x445/0x700 mm/memory.c:2133
>>   kasan_populate_vmalloc+0x68/0x90 mm/kasan/common.c:791
>>   pcpu_get_vm_areas+0x3c77/0x3f00 mm/vmalloc.c:3439
>>   pcpu_create_chunk+0x24e/0x7f0 mm/percpu-vm.c:340
>>   pcpu_balance_workfn+0xf1b/0x1310 mm/percpu.c:1934
>>   process_one_work+0x9af/0x1740 kernel/workqueue.c:2264
>>   worker_thread+0x98/0xe40 kernel/workqueue.c:2410
>>   kthread+0x361/0x430 kernel/kthread.c:255
>>   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
> 
> Replace the blocking gfp mask with a non-blocking one to survive
> checks like might_sleep.
> 
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -759,7 +759,7 @@ static int kasan_populate_vmalloc_pte(pt
>  	if (likely(!pte_none(*ptep)))
>  		return 0;
>  
> -	page = __get_free_page(GFP_KERNEL);
> +	page = __get_free_page(GFP_NOWAIT);
>  	if (!page)
>  		return -ENOMEM;
>  

Nope. This change would survive might_sleep() check, but the caller is
expecting that this is __GFP_NOFAIL allocation. Even if the caller can
tolerate allocation failures, __GFP_NOWARN should be added in order to
avoid flooding of allocation failure messages.

        /* insert all vm's */
        spin_lock(&vmap_area_lock);
        for (area = 0; area < nr_vms; area++) {
                insert_vmap_area(vas[area], &vmap_area_root, &vmap_area_list);

                setup_vmalloc_vm_locked(vms[area], vas[area], VM_ALLOC,
                                 pcpu_get_vm_areas);

                /* assume success here */
                kasan_populate_vmalloc(sizes[area], vms[area]);
        }
        spin_unlock(&vmap_area_lock);