[kernel-hardening] [PATCH 27/38] sctp: Copy struct sctp_sock.autoclose to userspace using put_user()

Kees Cook
2018-01-11T02:02:59Z

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]
Cc: Vlad Yasevich <vyasevich@gmail.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: linux-sctp@vger.kernel.org
Cc: netdev@vger.kernel.org
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 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