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SubjectRe: [PATCH] mm/kasan: Don't vfree() nonexistent vm_area.
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On 18.05.2018 17:57, David Hildenbrand wrote:
> On 01.02.2018 17:33, Andrey Ryabinin wrote:
>> KASAN uses different routines to map shadow for hot added memory and memory
>> obtained in boot process. Attempt to offline memory onlined by normal boot
>> process leads to this:
>>
>> Trying to vfree() nonexistent vm area (000000005d3b34b9)
>> WARNING: CPU: 2 PID: 13215 at mm/vmalloc.c:1525 __vunmap+0x147/0x190
>>
>> Call Trace:
>> kasan_mem_notifier+0xad/0xb9
>> notifier_call_chain+0x166/0x260
>> __blocking_notifier_call_chain+0xdb/0x140
>> __offline_pages+0x96a/0xb10
>> memory_subsys_offline+0x76/0xc0
>> device_offline+0xb8/0x120
>> store_mem_state+0xfa/0x120
>> kernfs_fop_write+0x1d5/0x320
>> __vfs_write+0xd4/0x530
>> vfs_write+0x105/0x340
>> SyS_write+0xb0/0x140
>>
>> Obviously we can't call vfree() to free memory that wasn't allocated via
>> vmalloc(). Use find_vm_area() to see if we can call vfree().
>>
>> Unfortunately it's a bit tricky to properly unmap and free shadow allocated
>> during boot, so we'll have to keep it. If memory will come online again
>> that shadow will be reused.
>>
>
> While debugging kasan memory hotplug problems I am having, stumbled over
> this patch.
>
> Couldn't we handle that via VM_KASAN like in kasan_module_alloc/free
> instead?
>

Just realized that this will most probably not work. So please ignore my
comment for now :)

--

Thanks,

David / dhildenb

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