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

From: Kees Cook
Date: Mon Jun 19 2017 - 19:37:11 EST

From: David Windsor <dave@xxxxxxxxxxxx>

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@xxxxxxxxxxxx>
[kees: adjust commit log]
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
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;