[PATCH 16/23] net: copy struct sctp_sock.autoclose to userspace using put_user()

From	Kees Cook <keescook@chromium.org>
Newsgroups	linux.kernel
Subject	[PATCH 16/23] net: copy struct sctp_sock.autoclose to userspace using put_user()
Date	2017-06-20 01:40 +0200
Message-ID	<tUeqZ-QH-11@gated-at.bofh.it> (permalink)
References	<tUeqZ-QH-7@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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From: David Windsor <dave@nullcore.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@nullcore.net>
[kees: adjust commit log]
Signed-off-by: Kees Cook <keescook@chromium.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 0defc0c76552..e94c141bcf82 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -4883,7 +4883,7 @@ 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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[PATCH 16/23] net: copy struct sctp_sock.autoclose to userspace using put_user() Kees Cook <keescook@chromium.org> - 2017-06-20 01:40 +0200

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