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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 <richardcochran@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent cfd1979e

drivers/ptp/ptp_chardev.c

+17 −5
Original line number Diff line number Diff line
@@ -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 = 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) {

		mutex_unlock(&ptp->tsevq_mux);

		return -ENOMEM;

	}



	spin_lock_irqsave(&queue->lock, flags);



	qcnt = queue_cnt(queue);
@@ -185,8 +195,10 @@ ssize_t ptp_read(struct posix_clock *pc, 


	mutex_unlock(&ptp->tsevq_mux);



	result = cnt;

	if (copy_to_user(buf, event, cnt))

		return -EFAULT;

		result = -EFAULT;



	return cnt;

	kfree(event);

	return result;

}