compat_ioctl: handle PPPIOCGIDLE for 64-bit time_t

The ppp_idle structure is defined in terms of __kernel_time_t, which is
defined as 'long' on all architectures, and this usage is not affected
by the y2038 problem since it transports a time interval rather than an
absolute time.

However, the ppp user space defines the same structure as time_t, which
may be 64-bit wide on new libc versions even on 32-bit architectures.

It's easy enough to just handle both possible structure layouts on
all architectures, to deal with the possibility that a user space ppp
implementation comes with its own ppp_idle structure definition, as well
as to document the fact that the driver is y2038-safe.

Doing this also avoids the need for a special compat mode translation,
since 32-bit and 64-bit kernels now support the same interfaces.  The old
32-bit structure is also available on native 64-bit architectures now,
but this is harmless.

Cc: netdev@vger.kernel.org
Cc: linux-ppp@vger.kernel.org
Cc: Paul Mackerras <paulus@samba.org>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Documentation/networking/ppp_generic.txt

@@ -378,6 +378,8 @@ an interface unit are:
   CONFIG_PPP_FILTER option is enabled, the set of packets which reset
   the transmit and receive idle timers is restricted to those which
   pass the `active' packet filter.
+  Two versions of this command exist, to deal with user space
+  expecting times as either 32-bit or 64-bit time_t seconds.
 
 * PPPIOCSMAXCID sets the maximum connection-ID parameter (and thus the
   number of connection slots) for the TCP header compressor and

drivers/net/ppp/ppp_generic.c

@@ -612,7 +612,8 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	struct ppp_file *pf;
 	struct ppp *ppp;
 	int err = -EFAULT, val, val2, i;
-	struct ppp_idle idle;
+	struct ppp_idle32 idle32;
+	struct ppp_idle64 idle64;
 	struct npioctl npi;
 	int unit, cflags;
 	struct slcompress *vj;
@@ -735,10 +736,18 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		err = 0;
 		break;
 
-	case PPPIOCGIDLE:
-		idle.xmit_idle = (jiffies - ppp->last_xmit) / HZ;
-		idle.recv_idle = (jiffies - ppp->last_recv) / HZ;
-		if (copy_to_user(argp, &idle, sizeof(idle)))
+	case PPPIOCGIDLE32:
+                idle32.xmit_idle = (jiffies - ppp->last_xmit) / HZ;
+                idle32.recv_idle = (jiffies - ppp->last_recv) / HZ;
+                if (copy_to_user(argp, &idle32, sizeof(idle32)))
+			break;
+		err = 0;
+		break;
+
+	case PPPIOCGIDLE64:
+		idle64.xmit_idle = (jiffies - ppp->last_xmit) / HZ;
+		idle64.recv_idle = (jiffies - ppp->last_recv) / HZ;
+		if (copy_to_user(argp, &idle64, sizeof(idle64)))
 			break;
 		err = 0;
 		break;

fs/compat_ioctl.c

@@ -52,6 +52,7 @@
 
 #include <linux/sort.h>
 
+#ifdef CONFIG_BLOCK
 static int do_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	int err;
@@ -63,7 +64,6 @@ static int do_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	return vfs_ioctl(file, cmd, arg);
 }
 
-#ifdef CONFIG_BLOCK
 struct compat_sg_req_info { /* used by SG_GET_REQUEST_TABLE ioctl() */
 	char req_state;
 	char orphan;
@@ -99,33 +99,6 @@ static int sg_grt_trans(struct file *file,
 }
 #endif /* CONFIG_BLOCK */
 
-struct ppp_idle32 {
-	compat_time_t xmit_idle;
-	compat_time_t recv_idle;
-};
-#define PPPIOCGIDLE32		_IOR('t', 63, struct ppp_idle32)
-
-static int ppp_gidle(struct file *file, unsigned int cmd,
-		struct ppp_idle32 __user *idle32)
-{
-	struct ppp_idle __user *idle;
-	__kernel_time_t xmit, recv;
-	int err;
-
-	idle = compat_alloc_user_space(sizeof(*idle));
-
-	err = do_ioctl(file, PPPIOCGIDLE, (unsigned long) idle);
-
-	if (!err) {
-		if (get_user(xmit, &idle->xmit_idle) ||
-		    get_user(recv, &idle->recv_idle) ||
-		    put_user(xmit, &idle32->xmit_idle) ||
-		    put_user(recv, &idle32->recv_idle))
-			err = -EFAULT;
-	}
-	return err;
-}
-
 /*
  * simple reversible transform to make our table more evenly
  * distributed after sorting.
@@ -192,7 +165,8 @@ COMPATIBLE_IOCTL(PPPIOCGDEBUG)
 COMPATIBLE_IOCTL(PPPIOCSDEBUG)
 /* PPPIOCSPASS is translated */
 /* PPPIOCSACTIVE is translated */
-/* PPPIOCGIDLE is translated */
+COMPATIBLE_IOCTL(PPPIOCGIDLE32)
+COMPATIBLE_IOCTL(PPPIOCGIDLE64)
 COMPATIBLE_IOCTL(PPPIOCNEWUNIT)
 COMPATIBLE_IOCTL(PPPIOCATTACH)
 COMPATIBLE_IOCTL(PPPIOCDETACH)
@@ -214,16 +188,14 @@ COMPATIBLE_IOCTL(PPPIOCGL2TPSTATS)
 static long do_ioctl_trans(unsigned int cmd,
 		 unsigned long arg, struct file *file)
 {
+#ifdef CONFIG_BLOCK
 	void __user *argp = compat_ptr(arg);
 
 	switch (cmd) {
-	case PPPIOCGIDLE32:
-		return ppp_gidle(file, cmd, argp);
-#ifdef CONFIG_BLOCK
 	case SG_GET_REQUEST_TABLE:
 		return sg_grt_trans(file, cmd, argp);
-#endif
 	}
+#endif
 
 	return -ENOIOCTLCMD;
 }

include/uapi/linux/ppp-ioctl.h

@@ -104,6 +104,8 @@ struct pppol2tp_ioc_stats {
 #define PPPIOCGDEBUG	_IOR('t', 65, int)	/* Read debug level */
 #define PPPIOCSDEBUG	_IOW('t', 64, int)	/* Set debug level */
 #define PPPIOCGIDLE	_IOR('t', 63, struct ppp_idle) /* get idle time */
+#define PPPIOCGIDLE32	_IOR('t', 63, struct ppp_idle32) /* 32-bit times */
+#define PPPIOCGIDLE64	_IOR('t', 63, struct ppp_idle64) /* 64-bit times */
 #define PPPIOCNEWUNIT	_IOWR('t', 62, int)	/* create new ppp unit */
 #define PPPIOCATTACH	_IOW('t', 61, int)	/* attach to ppp unit */
 #define PPPIOCDETACH	_IOW('t', 60, int)	/* obsolete, do not use */

include/uapi/linux/ppp_defs.h

@@ -142,10 +142,24 @@ struct ppp_comp_stats {
 /*
  * The following structure records the time in seconds since
  * the last NP packet was sent or received.
+ *
+ * Linux implements both 32-bit and 64-bit time_t versions
+ * for compatibility with user space that defines ppp_idle
+ * based on the libc time_t.
  */
 struct ppp_idle {
     __kernel_time_t xmit_idle;	/* time since last NP packet sent */
     __kernel_time_t recv_idle;	/* time since last NP packet received */
 };
 
+struct ppp_idle32 {
+    __s32 xmit_idle;		/* time since last NP packet sent */
+    __s32 recv_idle;		/* time since last NP packet received */
+};
+
+struct ppp_idle64 {
+    __s64 xmit_idle;		/* time since last NP packet sent */
+    __s64 recv_idle;		/* time since last NP packet received */
+};
+
 #endif /* _UAPI_PPP_DEFS_H_ */