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From: Toshiaki Makita <toshiaki.makita1@gmail.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.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 21:59:20 +0900
Message-ID: <fb895684-c863-e580-f36a-30722c480b41@gmail.com> (raw)
In-Reply-To: <87sgscbc5d.fsf@toke.dk>

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

  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 [this message]
2019-06-14 13:09         ` Toke Høiland-Jørgensen
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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