Re: [PATCH 1/1] gtp: fix use-after-free and null-ptr-deref in gtp_genl_dump_pdp()

From: kovalev@altlinux.org
To: Eric Dumazet <edumazet@google.com>
Cc: pablo@netfilter.org, laforge@gnumonks.org, davem@davemloft.net,
	kuba@kernel.org, pabeni@redhat.com,
	osmocom-net-gprs@lists.osmocom.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, nickel@altlinux.org,
	oficerovas@altlinux.org, dutyrok@altlinux.org
Subject: Re: [PATCH 1/1] gtp: fix use-after-free and null-ptr-deref in gtp_genl_dump_pdp()
Date: Wed, 14 Feb 2024 19:50:51 +0300	[thread overview]
Message-ID: <6cbbecf1-eba1-f3e1-259a-24df71f44785@basealt.ru> (raw)
In-Reply-To: <CANn89iJ4hVyRHiZXWTiW9ftyN8PFDaWiZnzE7GVAzu1dT78Daw@mail.gmail.com>

09.02.2024 22:21, Eric Dumazet wrote:

> Maybe, but the patch is not good, I think I and Pablo gave feedback on this ?
>
> Please trace __netlink_dump_start() content of control->module
>
> gtp_genl_family.module should be set, and we should get it.
>
> Otherwise, if the bug is in the core, we would need a dozen of 'work
> arounds because it is better than nothing'
>
> Thank you.

Thanks.

I tracked the moment when the __netlink_dump_start() function was 
called, it turned out that in the gtp_init() initialization function 
before registering pernet subsystem (gtp_net_ops), therefore, outdated 
data is used, which leads to a crash.

The documentation says that ops structure must be assigned before 
registering a generic netlink family [1].

I have fixed and sent a new patch [2].

[1] 
https://elixir.bootlin.com/linux/v6.8-rc4/source/net/netlink/genetlink.c#L773

[2] 
https://lore.kernel.org/netdev/20240214162733.34214-1-kovalev@altlinux.org/T/#u

-- 
Regards,
Vasiliy Kovalev