* [PATCH] rtc-mc146818-lib: fix locking in mc146818_set_time
@ 2022-02-20 9:04 Mateusz Jończyk
2022-03-08 16:38 ` Alexandre Belloni
0 siblings, 1 reply; 2+ messages in thread
From: Mateusz Jończyk @ 2022-02-20 9:04 UTC (permalink / raw)
To: linux-rtc, linux-kernel
Cc: Mateusz Jończyk, Alessandro Zummo, Alexandre Belloni,
Thomas Gleixner, stable
In mc146818_set_time(), CMOS_READ(RTC_CONTROL) was performed without the
rtc_lock taken, which is required for CMOS accesses. Fix this.
Nothing in kernel modifies RTC_DM_BINARY, so a separate critical section
is allowed here.
Fixes: dcf257e92622 ("rtc: mc146818: Reduce spinlock section in mc146818_set_time()")
Signed-off-by: Mateusz Jończyk <mat.jonczyk@o2.pl>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
---
drivers/rtc/rtc-mc146818-lib.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c
index ae9f131b43c0..562f99b664a2 100644
--- a/drivers/rtc/rtc-mc146818-lib.c
+++ b/drivers/rtc/rtc-mc146818-lib.c
@@ -232,8 +232,10 @@ int mc146818_set_time(struct rtc_time *time)
if (yrs >= 100)
yrs -= 100;
- if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY)
- || RTC_ALWAYS_BCD) {
+ spin_lock_irqsave(&rtc_lock, flags);
+ save_control = CMOS_READ(RTC_CONTROL);
+ spin_unlock_irqrestore(&rtc_lock, flags);
+ if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
sec = bin2bcd(sec);
min = bin2bcd(min);
hrs = bin2bcd(hrs);
base-commit: 754e0b0e35608ed5206d6a67a791563c631cec07
--
2.25.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] rtc-mc146818-lib: fix locking in mc146818_set_time
2022-02-20 9:04 [PATCH] rtc-mc146818-lib: fix locking in mc146818_set_time Mateusz Jończyk
@ 2022-03-08 16:38 ` Alexandre Belloni
0 siblings, 0 replies; 2+ messages in thread
From: Alexandre Belloni @ 2022-03-08 16:38 UTC (permalink / raw)
To: linux-kernel, Mateusz Jończyk, linux-rtc
Cc: Alexandre Belloni, Thomas Gleixner, stable, Alessandro Zummo
On Sun, 20 Feb 2022 10:04:03 +0100, Mateusz Jończyk wrote:
> In mc146818_set_time(), CMOS_READ(RTC_CONTROL) was performed without the
> rtc_lock taken, which is required for CMOS accesses. Fix this.
>
> Nothing in kernel modifies RTC_DM_BINARY, so a separate critical section
> is allowed here.
>
>
> [...]
Applied, thanks!
[1/1] rtc-mc146818-lib: fix locking in mc146818_set_time
commit: c63cdb340a7e0bd3734f9f8e27f082a054b45887
Best regards,
--
Alexandre Belloni <alexandre.belloni@bootlin.com>
^ permalink raw reply [flat|nested] 2+ messages in thread
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2022-02-20 9:04 [PATCH] rtc-mc146818-lib: fix locking in mc146818_set_time Mateusz Jończyk
2022-03-08 16:38 ` Alexandre Belloni
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