Commit c7ec0bad authored by Richard Cochran's avatar Richard Cochran Committed by David S. Miller
Browse files

ptp: reduce stack usage when reading external time stamps

This patch removes the large buffer from the stack of the read file
operation and replaces it with a kmalloced buffer.

Signed-off-by: default avatarRichard Cochran <>
Signed-off-by: default avatarDavid S. Miller <>
parent cfd1979e
......@@ -21,6 +21,7 @@
#include <linux/posix-clock.h>
#include <linux/poll.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include "ptp_private.h"
......@@ -136,20 +137,23 @@ unsigned int ptp_poll(struct posix_clock *pc, struct file *fp, poll_table *wait)
return queue_cnt(&ptp->tsevq) ? POLLIN : 0;
#define EXTTS_BUFSIZE (PTP_BUF_TIMESTAMPS * sizeof(struct ptp_extts_event))
ssize_t ptp_read(struct posix_clock *pc,
uint rdflags, char __user *buf, size_t cnt)
struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
struct timestamp_event_queue *queue = &ptp->tsevq;
struct ptp_extts_event event[PTP_BUF_TIMESTAMPS];
struct ptp_extts_event *event;
unsigned long flags;
size_t qcnt, i;
int result;
if (cnt % sizeof(struct ptp_extts_event) != 0)
return -EINVAL;
if (cnt > sizeof(event))
cnt = sizeof(event);
if (cnt > EXTTS_BUFSIZE)
cnt = cnt / sizeof(struct ptp_extts_event);
......@@ -167,6 +171,12 @@ ssize_t ptp_read(struct posix_clock *pc,
return -ENODEV;
event = kmalloc(EXTTS_BUFSIZE, GFP_KERNEL);
if (!event) {
return -ENOMEM;
spin_lock_irqsave(&queue->lock, flags);
qcnt = queue_cnt(queue);
......@@ -185,8 +195,10 @@ ssize_t ptp_read(struct posix_clock *pc,
result = cnt;
if (copy_to_user(buf, event, cnt))
return -EFAULT;
result = -EFAULT;
return cnt;
return result;
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