linux-kernel - Re: [PATCH 1/1] gtp: fix use-after-free and null-ptr-deref in gtp_genl_dump

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Date: Wed, 14 Feb 2024 19:50:51 +0300
From: kovalev@...linux.org
To: Eric Dumazet <edumazet@...gle.com>
Cc: pablo@...filter.org, laforge@...monks.org, davem@...emloft.net,
 kuba@...nel.org, pabeni@...hat.com, osmocom-net-gprs@...ts.osmocom.org,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org, nickel@...linux.org,
 oficerovas@...linux.org, dutyrok@...linux.org
Subject: Re: [PATCH 1/1] gtp: fix use-after-free and null-ptr-deref in
 gtp_genl_dump_pdp()

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before registering pernet subsystem (gtp_net_ops), therefore, outdated 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