netdev - Re: [net-next v2] tcp: Explicitly mark reserved field in tcp_zerocopy

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 8 Feb 2021 18:53:23 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     David Ahern <dsahern@...il.com>
Cc:     Leon Romanovsky <leon@...nel.org>,
        Arjun Roy <arjunroy.kdev@...il.com>, davem@...emloft.net,
        netdev@...r.kernel.org, arjunroy@...gle.com, edumazet@...gle.com,
        soheil@...gle.com
Subject: Re: [net-next v2] tcp: Explicitly mark reserved field in
 tcp_zerocopy_receive args.

On Mon, 8 Feb 2021 19:24:05 -0700 David Ahern wrote:
> On 2/8/21 11:41 AM, Jakub Kicinski wrote:
> > On Sun, 7 Feb 2021 10:26:54 +0200 Leon Romanovsky wrote:  
> >> There is a check that len is not larger than zs and users can't give
> >> large buffer.
> >>
> >> I would say that is pretty safe to write "if (zc.reserved)".  
> > 
> > Which check? There's a check which truncates (writes back to user space
> > len = min(len, sizeof(zc)). Application can still pass garbage beyond
> > sizeof(zc) and syscall may start failing in the future if sizeof(zc)
> > changes.
> 
> That would be the case for new userspace on old kernel. Extending the
> check to the end of the struct would guarantee new userspace can not ask
> for something that the running kernel does not understand.

Indeed, so we're agreeing that check_zeroed_user() is needed before
original optlen from user space gets truncated?