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Date: Wed, 10 Jan 2018 18:02:59 -0800
From: Kees Cook <keescook@...omium.org>
To: linux-kernel@...r.kernel.org
Cc: Kees Cook <keescook@...omium.org>,
	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>,
	Laura Abbott <labbott@...hat.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: [PATCH 27/38] sctp: Copy struct sctp_sock.autoclose to userspace using put_user()

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.

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;
 }
-- 
2.7.4

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