ptp: reduce stack usage when measuring the system time offset

This patch removes the large buffer from the stack of the system
offset ioctl and replaces it with a kmalloced buffer.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
index 9d7542e..34a0c60 100644 (file)
--- a/drivers/ptp/ptp_chardev.c
+++ b/drivers/ptp/ptp_chardev.c
@@ -34,7 +34,7 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
 {
        struct ptp_clock_caps caps;
        struct ptp_clock_request req;
-       struct ptp_sys_offset sysoff;
+       struct ptp_sys_offset *sysoff = NULL;
        struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
        struct ptp_clock_info *ops = ptp->info;
        struct ptp_clock_time *pct;
@@ -94,17 +94,22 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
                break;
 
        case PTP_SYS_OFFSET:
-               if (copy_from_user(&sysoff, (void __user *)arg,
-                                  sizeof(sysoff))) {
+               sysoff = kmalloc(sizeof(*sysoff), GFP_KERNEL);
+               if (!sysoff) {
+                       err = -ENOMEM;
+                       break;
+               }
+               if (copy_from_user(sysoff, (void __user *)arg,
+                                  sizeof(*sysoff))) {
                        err = -EFAULT;
                        break;
                }
-               if (sysoff.n_samples > PTP_MAX_SAMPLES) {
+               if (sysoff->n_samples > PTP_MAX_SAMPLES) {
                        err = -EINVAL;
                        break;
                }
-               pct = &sysoff.ts[0];
-               for (i = 0; i < sysoff.n_samples; i++) {
+               pct = &sysoff->ts[0];
+               for (i = 0; i < sysoff->n_samples; i++) {
                        getnstimeofday(&ts);
                        pct->sec = ts.tv_sec;
                        pct->nsec = ts.tv_nsec;
@@ -117,7 +122,7 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
                getnstimeofday(&ts);
                pct->sec = ts.tv_sec;
                pct->nsec = ts.tv_nsec;
-               if (copy_to_user((void __user *)arg, &sysoff, sizeof(sysoff)))
+               if (copy_to_user((void __user *)arg, sysoff, sizeof(*sysoff)))
                        err = -EFAULT;
                break;
 
@@ -125,6 +130,8 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
                err = -ENOTTY;
                break;
        }
+
+       kfree(sysoff);
        return err;
 }