[PATCH 4.19 39/45] compat_ioctl: pppoe: fix PPPOEIOCSFWD handling

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Arnd Bergmann <arnd@arndb.de>

[ Upstream commit 055d88242a6046a1ceac3167290f054c72571cd9 ]

Support for handling the PPPOEIOCSFWD ioctl in compat mode was added in
linux-2.5.69 along with hundreds of other commands, but was always broken
sincen only the structure is compatible, but the command number is not,
due to the size being sizeof(size_t), or at first sizeof(sizeof((struct
sockaddr_pppox)), which is different on 64-bit architectures.

Guillaume Nault adds:

  And the implementation was broken until 2016 (see 29e73269aa4d ("pppoe:
  fix reference counting in PPPoE proxy")), and nobody ever noticed. I
  should probably have removed this ioctl entirely instead of fixing it.
  Clearly, it has never been used.

Fix it by adding a compat_ioctl handler for all pppoe variants that
translates the command number and then calls the regular ioctl function.

All other ioctl commands handled by pppoe are compatible between 32-bit
and 64-bit, and require compat_ptr() conversion.

This should apply to all stable kernels.

Acked-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/ppp/pppoe.c  |    3 +++
 drivers/net/ppp/pppox.c  |   13 +++++++++++++
 drivers/net/ppp/pptp.c   |    3 +++
 fs/compat_ioctl.c        |    3 ---
 include/linux/if_pppox.h |    3 +++
 net/l2tp/l2tp_ppp.c      |    3 +++
 6 files changed, 25 insertions(+), 3 deletions(-)

--- a/drivers/net/ppp/pppoe.c
+++ b/drivers/net/ppp/pppoe.c
@@ -1120,6 +1120,9 @@ static const struct proto_ops pppoe_ops
 	.recvmsg	= pppoe_recvmsg,
 	.mmap		= sock_no_mmap,
 	.ioctl		= pppox_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= pppox_compat_ioctl,
+#endif
 };
 
 static const struct pppox_proto pppoe_proto = {
--- a/drivers/net/ppp/pppox.c
+++ b/drivers/net/ppp/pppox.c
@@ -22,6 +22,7 @@
 #include <linux/string.h>
 #include <linux/module.h>
 #include <linux/kernel.h>
+#include <linux/compat.h>
 #include <linux/errno.h>
 #include <linux/netdevice.h>
 #include <linux/net.h>
@@ -103,6 +104,18 @@ int pppox_ioctl(struct socket *sock, uns
 
 EXPORT_SYMBOL(pppox_ioctl);
 
+#ifdef CONFIG_COMPAT
+int pppox_compat_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
+{
+	if (cmd == PPPOEIOCSFWD32)
+		cmd = PPPOEIOCSFWD;
+
+	return pppox_ioctl(sock, cmd, (unsigned long)compat_ptr(arg));
+}
+
+EXPORT_SYMBOL(pppox_compat_ioctl);
+#endif
+
 static int pppox_create(struct net *net, struct socket *sock, int protocol,
 			int kern)
 {
--- a/drivers/net/ppp/pptp.c
+++ b/drivers/net/ppp/pptp.c
@@ -633,6 +633,9 @@ static const struct proto_ops pptp_ops =
 	.recvmsg    = sock_no_recvmsg,
 	.mmap       = sock_no_mmap,
 	.ioctl      = pppox_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl = pppox_compat_ioctl,
+#endif
 };
 
 static const struct pppox_proto pppox_pptp_proto = {
--- a/fs/compat_ioctl.c
+++ b/fs/compat_ioctl.c
@@ -894,9 +894,6 @@ COMPATIBLE_IOCTL(PPPIOCDISCONN)
 COMPATIBLE_IOCTL(PPPIOCATTCHAN)
 COMPATIBLE_IOCTL(PPPIOCGCHAN)
 COMPATIBLE_IOCTL(PPPIOCGL2TPSTATS)
-/* PPPOX */
-COMPATIBLE_IOCTL(PPPOEIOCSFWD)
-COMPATIBLE_IOCTL(PPPOEIOCDFWD)
 /* Big A */
 /* sparc only */
 /* Big Q for sound/OSS */
--- a/include/linux/if_pppox.h
+++ b/include/linux/if_pppox.h
@@ -84,6 +84,9 @@ extern int register_pppox_proto(int prot
 extern void unregister_pppox_proto(int proto_num);
 extern void pppox_unbind_sock(struct sock *sk);/* delete ppp-channel binding */
 extern int pppox_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg);
+extern int pppox_compat_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg);
+
+#define PPPOEIOCSFWD32    _IOW(0xB1 ,0, compat_size_t)
 
 /* PPPoX socket states */
 enum {
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -1686,6 +1686,9 @@ static const struct proto_ops pppol2tp_o
 	.recvmsg	= pppol2tp_recvmsg,
 	.mmap		= sock_no_mmap,
 	.ioctl		= pppox_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl = pppox_compat_ioctl,
+#endif
 };
 
 static const struct pppox_proto pppol2tp_proto = {