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>

1 files changed, 14 insertions, 7 deletions

diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
index 9d7542efb175..34a0c607318e 100644
--- 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;
 }