ptp: Validate requests to enable time stamping of external signals.

Commit 41560658 ("PTP: introduce new versions of IOCTLs")
introduced a new external time stamp ioctl that validates the flags.
This patch extends the validation to ensure that at least one rising
or falling edge flag is set when enabling external time stamps.
Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/ptp/ptp_chardev.c

@@ -149,11 +149,19 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
 			err = -EFAULT;
 			break;
 		}
-		if (((req.extts.flags & ~PTP_EXTTS_VALID_FLAGS) ||
-			req.extts.rsv[0] || req.extts.rsv[1]) &&
-			cmd == PTP_EXTTS_REQUEST2) {
-			err = -EINVAL;
-			break;
+		if (cmd == PTP_EXTTS_REQUEST2) {
+			/* Make sure no reserved bit is set. */
+			if ((req.extts.flags & ~PTP_EXTTS_VALID_FLAGS) ||
+			    req.extts.rsv[0] || req.extts.rsv[1]) {
+				err = -EINVAL;
+				break;
+			}
+			/* Ensure one of the rising/falling edge bits is set. */
+			if ((req.extts.flags & PTP_ENABLE_FEATURE) &&
+			    (req.extts.flags & PTP_EXTTS_EDGES) == 0) {
+				err = -EINVAL;
+				break;
+			}
 		} else if (cmd == PTP_EXTTS_REQUEST) {
 			req.extts.flags &= PTP_EXTTS_V1_VALID_FLAGS;
 			req.extts.rsv[0] = 0;

include/uapi/linux/ptp_clock.h

@@ -31,6 +31,7 @@
 #define PTP_ENABLE_FEATURE (1<<0)
 #define PTP_RISING_EDGE    (1<<1)
 #define PTP_FALLING_EDGE   (1<<2)
+#define PTP_EXTTS_EDGES    (PTP_RISING_EDGE | PTP_FALLING_EDGE)
 
 /*
  * flag fields valid for the new PTP_EXTTS_REQUEST2 ioctl.