linux-kernel - Re: [PATCH net] xfrm: Fix ignored return value in xfrm6

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Date:   Mon, 7 Nov 2022 10:06:48 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Chen Zhongjin <chenzhongjin@...wei.com>
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        steffen.klassert@...unet.com, herbert@...dor.apana.org.au,
        davem@...emloft.net, yoshfuji@...ux-ipv6.org, dsahern@...nel.org,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        mkubecek@...e.cz
Subject: Re: [PATCH net] xfrm: Fix ignored return value in xfrm6_init()

On Mon, Nov 07, 2022 at 11:22:40AM +0800, Chen Zhongjin wrote:
> Hi,
> 
> On 2022/11/7 3:08, Leon Romanovsky wrote:
> > On Thu, Nov 03, 2022 at 05:07:13PM +0800, Chen Zhongjin wrote:
> > > When IPv6 module initializing in xfrm6_init(), register_pernet_subsys()
> > > is possible to fail but its return value is ignored.
> > > 
> > > If IPv6 initialization fails later and xfrm6_fini() is called,
> > > removing uninitialized list in xfrm6_net_ops will cause null-ptr-deref:
> > > 
> > > KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
> > > CPU: 1 PID: 330 Comm: insmod
> > > RIP: 0010:unregister_pernet_operations+0xc9/0x450
> > > Call Trace:
> > >   <TASK>
> > >   unregister_pernet_subsys+0x31/0x3e
> > >   xfrm6_fini+0x16/0x30 [ipv6]
> > >   ip6_route_init+0xcd/0x128 [ipv6]
> > >   inet6_init+0x29c/0x602 [ipv6]
> > >   ...
> > > 
> > > Fix it by catching the error return value of register_pernet_subsys().
> > > 
> > > Fixes: 8d068875caca ("xfrm: make gc_thresh configurable in all namespaces")
> > > Signed-off-by: Chen Zhongjin <chenzhongjin@...wei.com>
> > > ---
> > >   net/ipv6/xfrm6_policy.c | 6 +++++-
> > >   1 file changed, 5 insertions(+), 1 deletion(-)
> > I see same error in net/ipv4/xfrm4_policy.c which introduced by same
> > commit mentioned in Fixes line.
> 
> It's true that in xfrm4_init() the ops->init is possible to fail as well.
> 
> However there is no error handling or exit path for ipv4, so IIUC the ops
> won't be unregistered anyway.
> 
> Considering that ipv4 don't handle most of error in initialization, maybe
> it's better to keep it as it is?

Yeah, makes sense.

Thanks,
Reviewed-by: Leon Romanovsky <leonro@...dia.com>