netdev - [PATCH] socket: fix struct ifreq size in compat ioctl

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Date:   Thu, 13 Sep 2018 13:49:09 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     netdev@...r.kernel.org
Cc:     Robert O'Callahan <robert@...llahan.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Johannes Berg <johannes.berg@...el.com>
Subject: [PATCH] socket: fix struct ifreq size in compat ioctl

From: Johannes Berg <johannes.berg@...el.com>

As reported by Reobert O'Callahan, since Viro's commit to kill
dev_ifsioc() we attempt to copy too much data in compat mode,
which may lead to EFAULT when the 32-bit version of struct ifreq
sits at/near the end of a page boundary, and the next page isn't
mapped.

Fix this by passing whether or not we're doing a compat call and
copying the appropriate size in/out, as we did before. This works
because only the embedded "struct ifmap" has different size, and
this is only used in SIOCGIFMAP/SIOCSIFMAP which has a different
handler. All other parts of the union are naturally compatible.

Fixes: bf4405737f9f ("kill dev_ifsioc()")
Reported-by: Robert O'Callahan <robert@...llahan.org>
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
---
 net/socket.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/net/socket.c b/net/socket.c
index e6945e318f02..cef0725a2aaf 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -941,7 +941,8 @@ void dlci_ioctl_set(int (*hook) (unsigned int, void __user *))
 EXPORT_SYMBOL(dlci_ioctl_set);
 
 static long sock_do_ioctl(struct net *net, struct socket *sock,
-				 unsigned int cmd, unsigned long arg)
+			  unsigned int cmd, unsigned long arg,
+			  bool compat)
 {
 	int err;
 	void __user *argp = (void __user *)arg;
@@ -967,11 +968,15 @@ static long sock_do_ioctl(struct net *net, struct socket *sock,
 	} else {
 		struct ifreq ifr;
 		bool need_copyout;
-		if (copy_from_user(&ifr, argp, sizeof(struct ifreq)))
+		if (copy_from_user(&ifr, argp,
+				   compat ? sizeof(struct compat_ifreq) :
+					    sizeof(struct ifreq)))
 			return -EFAULT;
 		err = dev_ioctl(net, cmd, &ifr, &need_copyout);
 		if (!err && need_copyout)
-			if (copy_to_user(argp, &ifr, sizeof(struct ifreq)))
+			if (copy_to_user(argp, &ifr,
+					 compat ? sizeof(struct compat_ifreq) :
+						  sizeof(struct ifreq)))
 				return -EFAULT;
 	}
 	return err;
@@ -1070,7 +1075,7 @@ static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
 			err = open_related_ns(&net->ns, get_net_ns);
 			break;
 		default:
-			err = sock_do_ioctl(net, sock, cmd, arg);
+			err = sock_do_ioctl(net, sock, cmd, arg, false);
 			break;
 		}
 	return err;
@@ -2750,7 +2755,7 @@ static int do_siocgstamp(struct net *net, struct socket *sock,
 	int err;
 
 	set_fs(KERNEL_DS);
-	err = sock_do_ioctl(net, sock, cmd, (unsigned long)&ktv);
+	err = sock_do_ioctl(net, sock, cmd, (unsigned long)&ktv, true);
 	set_fs(old_fs);
 	if (!err)
 		err = compat_put_timeval(&ktv, up);
@@ -2766,7 +2771,7 @@ static int do_siocgstampns(struct net *net, struct socket *sock,
 	int err;
 
 	set_fs(KERNEL_DS);
-	err = sock_do_ioctl(net, sock, cmd, (unsigned long)&kts);
+	err = sock_do_ioctl(net, sock, cmd, (unsigned long)&kts, true);
 	set_fs(old_fs);
 	if (!err)
 		err = compat_put_timespec(&kts, up);
@@ -3072,7 +3077,7 @@ static int routing_ioctl(struct net *net, struct socket *sock,
 	}
 
 	set_fs(KERNEL_DS);
-	ret = sock_do_ioctl(net, sock, cmd, (unsigned long) r);
+	ret = sock_do_ioctl(net, sock, cmd, (unsigned long) r, true);
 	set_fs(old_fs);
 
 out:
@@ -3185,7 +3190,7 @@ static int compat_sock_ioctl_trans(struct file *file, struct socket *sock,
 	case SIOCBONDSETHWADDR:
 	case SIOCBONDCHANGEACTIVE:
 	case SIOCGIFNAME:
-		return sock_do_ioctl(net, sock, cmd, arg);
+		return sock_do_ioctl(net, sock, cmd, arg, true);
 	}
 
 	return -ENOIOCTLCMD;
-- 
2.14.4