netdev - Re: [PATCH] net: Finish up ->msg_control{,

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Message-ID: <710ed5a2-1c3a-3fb1-c015-55ded320db30@arm.com>
Date:   Thu, 13 Apr 2023 10:34:48 +0200
From:   Kevin Brodsky <kevin.brodsky@....com>
To:     Christoph Hellwig <hch@....de>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH] net: Finish up ->msg_control{,_user} split

On 12/04/2023 17:25, Christoph Hellwig wrote:
> On Tue, Apr 11, 2023 at 01:26:25PM +0100, Kevin Brodsky wrote:
>> This patch is attempting to complete the split. Most issues are about
>> msg_control being used when in fact a user pointer is stored in the
>> union; msg_control_user is now used instead. An exception is made
>> for null checks, as it should be safe to use msg_control
>> unconditionally for that purpose.
> So all of the fixes looks good to me.
>
>> Additionally, a special situation in
>> cmsghdr_from_user_compat_to_kern() is addressed. There the input
>> struct msghdr holds a user pointer (msg_control_user), but a kernel
>> pointer is stored in msg_control when returning. msg_control_is_user
>> is now updated accordingly.
> But this is a small isolated real bugfix.  So I'd suggest to split
> this into a simple and easily backportable patch, and do the rest
> in another.
>
>> diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
>> index 2917dd8d198c..ae818ff46224 100644
>> --- a/net/ipv6/ipv6_sockglue.c
>> +++ b/net/ipv6/ipv6_sockglue.c
>> @@ -716,6 +716,7 @@ int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
>>                      goto done;
>>
>>              msg.msg_controllen = optlen;
>> +            msg.msg_control_is_user = false;
> And this is another one that has a real effect.

Thank you, both good points! Will split that up into a series of three
patches.

Kevin
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