linux-kernel - Re: RTC wakealarm write-only, still has 644 permissions

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Message-ID: <20071128232651.GD4947@elf.ucw.cz>
Date:	Thu, 29 Nov 2007 00:26:51 +0100
From:	Pavel Machek <pavel@....cz>
To:	David Brownell <david-b@...bell.net>
Cc:	rtc-linux@...glegroups.com,
	kernel list <linux-kernel@...r.kernel.org>,
	Alessandro Zummo <alessandro.zummo@...ertech.it>
Subject: Re: RTC wakealarm write-only, still has 644 permissions

Hi!

> rtc-sysfs.c: why this?
> 
>         if (alarm > now) {
>                 /* Avoid accidentally clobbering active alarms; we
> can't
>                  * entirely prevent that here, without even the
> minimal
>                  * locking from the /dev/rtcN api.
>                  */
>                 retval = rtc_read_alarm(rtc, &alm);
>                 if (retval < 0)
>                         return retval;
>                 if (alm.enabled)
>                         return -EBUSY;
> 
>                 alm.enabled = 1;
> 
> People should not be "accidentally" writing to sysfs files...

If I remove "accidental alarm modify" logic, I can actually use rtc to
wake up more than once per boot.

Signed-off-by: Pavel Machek <pavel@...e.cz>

diff --git a/drivers/rtc/rtc-sysfs.c b/drivers/rtc/rtc-sysfs.c
index 2ae0e83..ba5e806 100644
--- a/drivers/rtc/rtc-sysfs.c
+++ b/drivers/rtc/rtc-sysfs.c
@@ -149,16 +149,6 @@ rtc_sysfs_set_wakealarm(struct device *d
 
 	alarm = simple_strtoul(buf, NULL, 0);
 	if (alarm > now) {
-		/* Avoid accidentally clobbering active alarms; we can't
-		 * entirely prevent that here, without even the minimal
-		 * locking from the /dev/rtcN api.
-		 */
-		retval = rtc_read_alarm(rtc, &alm);
-		if (retval < 0)
-			return retval;
-		if (alm.enabled)
-			return -EBUSY;
-
 		alm.enabled = 1;
 	} else {
 		alm.enabled = 0;


-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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