[rtc-linux] [PATCH] drivers/rtc/rtc-m41t80.c: avoid out of range year values

[rtc-linux] [PATCH] drivers/rtc/rtc-m41t80.c: avoid out of range year values

[Stefan Christ]

Avoid saving an out of range year value to the RTC. Reading that value
from the RTC again returns a totally wrong time value. For Example

    $ timedatectl set-ntp no
    $ timedatectl set-time "1990-01-01 12:12:00"
    # Reboot
    rtc-m41t80 0-0068: setting system clock to 2090-01-01 12:12:35 UTC (3786955955)

Signed-off-by: Stefan Christ <s.christ@phytec.de>
---
 drivers/rtc/rtc-m41t80.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/rtc/rtc-m41t80.c b/drivers/rtc/rtc-m41t80.c
index a82937e..ae8bfae 100644
--- a/drivers/rtc/rtc-m41t80.c
+++ b/drivers/rtc/rtc-m41t80.c
@@ -176,7 +176,13 @@ static int m41t80_set_datetime(struct i2c_client *client, struct rtc_time *tm)
 		bin2bcd(tm->tm_mday) | (buf[M41T80_REG_DAY] & ~0x3f);
 	buf[M41T80_REG_MON] =
 		bin2bcd(tm->tm_mon + 1) | (buf[M41T80_REG_MON] & ~0x1f);
+
 	/* assume 20YY not 19YY */
+	if (!(100 <= tm->tm_year && tm->tm_year <= 199)) {
+		dev_err(&client->dev, "Year must be between 2000 and 2099. It's %d.\n",
+					tm->tm_year + 1900);
+		return -EINVAL;
+	}
 	buf[M41T80_REG_YEAR] = bin2bcd(tm->tm_year % 100);
 
 	if (i2c_transfer(client->adapter, msgs, 1) != 1) {
-- 
1.9.1

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[rtc-linux] Re: [PATCH] drivers/rtc/rtc-m41t80.c: avoid out of range year values

[Alexandre Belloni]

Hi,

On 08/03/2016 at 12:56:50 +0100, Stefan Christ wrote :
> Avoid saving an out of range year value to the RTC. Reading that value
> from the RTC again returns a totally wrong time value. For Example
> 
>     $ timedatectl set-ntp no
>     $ timedatectl set-time "1990-01-01 12:12:00"
>     # Reboot
>     rtc-m41t80 0-0068: setting system clock to 2090-01-01 12:12:35 UTC (3786955955)
> 
> Signed-off-by: Stefan Christ <s.christ@phytec.de>
> ---
>  drivers/rtc/rtc-m41t80.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/rtc/rtc-m41t80.c b/drivers/rtc/rtc-m41t80.c
> index a82937e..ae8bfae 100644
> --- a/drivers/rtc/rtc-m41t80.c
> +++ b/drivers/rtc/rtc-m41t80.c
> @@ -176,7 +176,13 @@ static int m41t80_set_datetime(struct i2c_client *client, struct rtc_time *tm)
>  		bin2bcd(tm->tm_mday) | (buf[M41T80_REG_DAY] & ~0x3f);
>  	buf[M41T80_REG_MON] =
>  		bin2bcd(tm->tm_mon + 1) | (buf[M41T80_REG_MON] & ~0x1f);
> +
>  	/* assume 20YY not 19YY */
> +	if (!(100 <= tm->tm_year && tm->tm_year <= 199)) {

This introduces a checkpatch warning, can you fix that and resend 

> +		dev_err(&client->dev, "Year must be between 2000 and 2099. It's %d.\n",
> +					tm->tm_year + 1900);

This is not properly aligned.

> +		return -EINVAL;
> +	}
>  	buf[M41T80_REG_YEAR] = bin2bcd(tm->tm_year % 100);
>  
>  	if (i2c_transfer(client->adapter, msgs, 1) != 1) {
> -- 
> 1.9.1
> 

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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