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From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Toshiaki Makita <toshiaki.makita1@gmail.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <jakub.kicinski@netronome.com>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	John Fastabend <john.fastabend@gmail.com>
Cc: netdev@vger.kernel.org, xdp-newbies@vger.kernel.org,
	bpf@vger.kernel.org, "Michael S. Tsirkin" <mst@redhat.com>,
	Jason Wang <jasowang@redhat.com>, David Ahern <dsahern@gmail.com>
Subject: Re: [PATCH bpf 1/3] devmap: Fix premature entry free on destroying map
Date: Fri, 14 Jun 2019 15:09:44 +0200
Message-ID: <87muikb9ev.fsf@toke.dk> (raw)
In-Reply-To: <fb895684-c863-e580-f36a-30722c480b41@gmail.com>

Toshiaki Makita <toshiaki.makita1@gmail.com> writes:

> 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.

Oh, no worries!

> I'm also not sure how to proceed in this case.

I guess we'll leave that up to the maintainers :)

-Toke

  reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-14  8:20 [PATCH bpf 0/3] Devmap fixes around memory and RCU Toshiaki Makita
2019-06-14  8:20 ` [PATCH bpf 1/3] devmap: Fix premature entry free on destroying map Toshiaki Makita
2019-06-14 11:04   ` Toke Høiland-Jørgensen
2019-06-14 12:10     ` Toke Høiland-Jørgensen
2019-06-14 12:59       ` Toshiaki Makita
2019-06-14 13:09         ` Toke Høiland-Jørgensen [this message]
2019-06-14 23:07           ` Daniel Borkmann
2019-06-15 10:10             ` Toke Høiland-Jørgensen
2019-06-14 12:20     ` Jesper Dangaard Brouer
2019-06-14  8:20 ` [PATCH bpf 2/3] devmap: Add missing bulk queue free Toshiaki Makita
2019-06-14 11:58   ` Jesper Dangaard Brouer
2019-06-14 13:03     ` Toshiaki Makita
2019-06-14  8:20 ` [PATCH bpf 3/3] devmap: Add missing RCU read lock on flush Toshiaki Makita
2019-06-14 11:07   ` Toke Høiland-Jørgensen

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