[PATCH] pps: locking scheme fix up for PPS_GETPARAMS.

Userland programs may read/write PPS parameters at same time and these
operations may corrupt PPS data.

Signed-off-by: Rodolfo Giometti <giometti.RemoveThis@linux.it>
Tested-by: Reg Clemens <clemens.RemoveThis@dwf.com>
---
drivers/pps/pps.c | 11 ++++++++---
1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
index fea17e7..ca5183b 100644
--- a/drivers/pps/pps.c
+++ b/drivers/pps/pps.c
@@ -71,9 +71,14 @@ static long pps_cdev_ioctl(struct file *file,
case PPS_GETPARAMS:
pr_debug("PPS_GETPARAMS: source %d\n", pps->id);

- /* Return current parameters */
- err = copy_to_user(uarg, &pps->params,
- sizeof(struct pps_kparams));
+ spin_lock_irq(&pps->lock);
+
+ /* Get the current parameters */
+ params = pps->params;
+
+ spin_unlock_irq(&pps->lock);
+
+ err = copy_to_user(uarg, &params, sizeof(struct pps_kparams));
if (err)
return -EFAULT;

--
1.6.3.3

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PPS events must be recorded according to PPS's mode settings.

If a process asks for (i.e.) capture-assert events only, when the PPS
client calls the pps_event() function to save the current PPS event,
we should verify the event type and then discard unwanted ones.

Also, without this patch userland processes waiting for a specific PPS
event (assert or clear but not both) may be awakened at wrong time.

Signed-off-by: Rodolfo Giometti <giometti.RemoveThis@linux.it>
Tested-by: William S. Brasher <billb958.RemoveThis@door.net>
Tested-by: Reg Clemens <clemens.RemoveThis@dwf.com>
---
drivers/pps/kapi.c | 20 +++++++++++++++-----
1 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c
index 35a0b19..2d414e2 100644
--- a/drivers/pps/kapi.c
+++ b/drivers/pps/kapi.c
@@ -271,6 +271,7 @@ void pps_event(int source, struct pps_ktime *ts, int event, void *data)
{
struct pps_device *pps;
unsigned long flags;
+ int captured = 0;

if ((event & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR)) == 0) {
printk(KERN_ERR "pps: unknown event (%x) for source %d\n",
@@ -293,7 +294,8 @@ void pps_event(int source, struct pps_ktime *ts, int event, void *data)

/* Check the event */
pps->current_mode = pps->params.mode;
- if (event & PPS_CAPTUREASSERT) {
+ if ((event & PPS_CAPTUREASSERT) &
+ (pps->params.mode & PPS_CAPTUREASSERT)) {
/* We have to add an offset? */
if (pps->params.mode & PPS_OFFSETASSERT)
pps_add_offset(ts, &pps->params.assert_off_tu);
@@ -303,8 +305,11 @@ void pps_event(int source, struct pps_ktime *ts, int event, void *data)
pps->assert_sequence++;
pr_debug("capture assert seq #%u for source %d\n",
pps->assert_sequence, source);
+
+ captured = ~0;
}
- if (event & PPS_CAPTURECLEAR) {
+ if ((event & PPS_CAPTURECLEAR) &
+ (pps->params.mode & PPS_CAPTURECLEAR)) {
/* We have to add an offset? */
if (pps->params.mode & PPS_OFFSETCLEAR)
pps_add_offset(ts, &pps->params.clear_off_tu);
@@ -314,12 +319,17 @@ void pps_event(int source, struct pps_ktime *ts, int event, void *data)
pps->clear_sequence++;
pr_debug("capture clear seq #%u for source %d\n",
pps->clear_sequence, source);
+
+ captured = ~0;
}

- pps->go = ~0;
- wake_up_interruptible(&pps->queue);
+ /* Wake up iif captured somthing */
+ if (captured) {
+ pps->go = ~0;
+ wake_up_interruptible(&pps->queue);

- kill_fasync(&pps->async_queue, SIGIO, POLL_IN);
+ kill_fasync(&pps->async_queue, SIGIO, POLL_IN);
+ }

spin_unlock_irqrestore(&pps->lock, flags);

--
1.6.0.4

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