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Date: Thu, 18 Jan 2018 13:31:42 -0800
From: Laura Abbott <labbott@...hat.com>
To: Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org
Cc: David Windsor <dave@...lcore.net>, Vlad Yasevich <vyasevich@...il.com>,
 Neil Horman <nhorman@...driver.com>, "David S. Miller"
 <davem@...emloft.net>, linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 Alexander Viro <viro@...iv.linux.org.uk>,
 Andrew Morton <akpm@...ux-foundation.org>, Andy Lutomirski
 <luto@...nel.org>, Christoph Hellwig <hch@...radead.org>,
 Christoph Lameter <cl@...ux.com>, Mark Rutland <mark.rutland@....com>,
 "Martin K. Petersen" <martin.petersen@...cle.com>,
 Paolo Bonzini <pbonzini@...hat.com>,
 Christian Borntraeger <borntraeger@...ibm.com>,
 Christoffer Dall <christoffer.dall@...aro.org>,
 Dave Kleikamp <dave.kleikamp@...cle.com>, Jan Kara <jack@...e.cz>,
 Luis de Bethencourt <luisbg@...nel.org>, Marc Zyngier
 <marc.zyngier@....com>, Rik van Riel <riel@...hat.com>,
 Matthew Garrett <mjg59@...gle.com>, linux-fsdevel@...r.kernel.org,
 linux-arch@...r.kernel.org, linux-mm@...ck.org,
 kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH 27/38] sctp: Copy struct sctp_sock.autoclose to userspace
 using put_user()

On 01/10/2018 06:02 PM, Kees Cook wrote:
> From: David Windsor <dave@...lcore.net>
> 
> The autoclose field can be copied with put_user(), so there is no need to
> use copy_to_user(). In both cases, hardened usercopy is being bypassed
> since the size is constant, and not open to runtime manipulation.
> 
> This patch is verbatim from Brad Spengler/PaX Team's PAX_USERCOPY
> whitelisting code in the last public patch of grsecurity/PaX based on my
> understanding of the code. Changes or omissions from the original code are
> mine and don't reflect the original grsecurity/PaX code.
> 

Just tried a quick rebase and it looks like this conflicts with
c76f97c99ae6 ("sctp: make use of pre-calculated len")
I don't think we can use put_user if we're copying via the full
len?

Thanks,
Laura

> Signed-off-by: David Windsor <dave@...lcore.net>
> [kees: adjust commit log]
> Cc: Vlad Yasevich <vyasevich@...il.com>
> Cc: Neil Horman <nhorman@...driver.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: linux-sctp@...r.kernel.org
> Cc: netdev@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>   net/sctp/socket.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index efbc8f52c531..15491491ec88 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -5011,7 +5011,7 @@ static int sctp_getsockopt_autoclose(struct sock *sk, int len, char __user *optv
>   	len = sizeof(int);
>   	if (put_user(len, optlen))
>   		return -EFAULT;
> -	if (copy_to_user(optval, &sctp_sk(sk)->autoclose, sizeof(int)))
> +	if (put_user(sctp_sk(sk)->autoclose, (int __user *)optval))
>   		return -EFAULT;
>   	return 0;
>   }
> 

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