Re: [PATCH bpf 1/3] devmap: Fix premature entry free on destroying map

[Toshiaki Makita <toshiaki.makita1@gmail.com>]

On 19/06/14 (金) 21:10:38, Toke Høiland-Jørgensen wrote:
> Toke Høiland-Jørgensen <toke@redhat.com> writes:
> 
>> Toshiaki Makita <toshiaki.makita1@gmail.com> writes:
>>
>>> dev_map_free() waits for flush_needed bitmap to be empty in order to
>>> ensure all flush operations have completed before freeing its entries.
>>> However the corresponding clear_bit() was called before using the
>>> entries, so the entries could be used after free.
>>>
>>> All access to the entries needs to be done before clearing the bit.
>>> It seems commit a5e2da6e9787 ("bpf: netdev is never null in
>>> __dev_map_flush") accidentally changed the clear_bit() and memory access
>>> order.
>>>
>>> Note that the problem happens only in __dev_map_flush(), not in
>>> dev_map_flush_old(). dev_map_flush_old() is called only after nulling
>>> out the corresponding netdev_map entry, so dev_map_free() never frees
>>> the entry thus no such race happens there.
>>>
>>> Fixes: a5e2da6e9787 ("bpf: netdev is never null in __dev_map_flush")
>>> Signed-off-by: Toshiaki Makita <toshiaki.makita1@gmail.com>
>>
>> I recently posted a patch[0] that gets rid of the bitmap entirely, so I
>> think you can drop this one...
> 
> Alternatively, since this entire series should probably go to stable, I
> can respin mine on top of it?

Indeed conflict will happen, as this is for 'bpf' not 'bpf-next'. Sorry 
for disturbing your work. I'm also not sure how to proceed in this case.

Toshiaki Makita