netdev - Re: [PATCHv2 net] ipv6: sr: fix invalid unregister error path

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Message-ID: <ZjuLplygL6JudnlF@Laptop-X1>
Date: Wed, 8 May 2024 22:26:46 +0800
From: Hangbin Liu <liuhangbin@...il.com>
To: Simon Horman <horms@...nel.org>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	David Ahern <dsahern@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Vasiliy Kovalev <kovalev@...linux.org>,
	Sabrina Dubroca <sd@...asysnail.net>,
	Guillaume Nault <gnault@...hat.com>
Subject: Re: [PATCHv2 net] ipv6: sr: fix invalid unregister error path

On Wed, May 08, 2024 at 10:40:53AM +0100, Simon Horman wrote:
> On Wed, May 08, 2024 at 10:55:02AM +0800, Hangbin Liu wrote:
> > The error path of seg6_init() is wrong in case CONFIG_IPV6_SEG6_LWTUNNEL
> > is not defined. In that case if seg6_hmac_init() fails, the
> > genl_unregister_family() isn't called.
> > 
> > At the same time, add seg6_local_exit() and fix the genl unregister order
> > in seg6_exit().
> 
> It seems that this fixes two, or perhaps three different problems.
> Perhaps we should consider two or three patches?

Yeah..
> 
> Also, could you explain the implications of changing the unregister order
> in the patch description: it should describe why a change is made.

Sure, I will.

> 
> > Fixes: 5559cea2d5aa ("ipv6: sr: fix possible use-after-free and null-ptr-deref")
> 
> I agree that the current manifestation of the first problem
> was introduced. But didn't a very similar problem exist before then?
> I suspect the fixes tag should refer to an earlier commit.

Yes, I will check previous commits.

> 
> > Reported-by: Guillaume Nault <gnault@...hat.com>
> > Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
> 
> I think these bugs are pretty good examples of why not
> to sprinkle #ifdef inside of functions - it makes the
> logic hard to reason with.
> 
> So while I agree that a minimal fix, along the lines of this patch, is
> suitable for 'net'. Could we consider, as a follow-up, refactoring the code
> to remove this #ifdef spaghetti? F.e. by providing dummy implementations
> of seg6_iptunnel_init()/seg6_iptunnel_exit() and so on.

Makes sense.

Thanks
Hangbin