diff mbox series

[next,V2] rtc: msc313: Fix unintentional sign extension issues with left shift of a u16

Message ID 20210928134654.991923-1-colin.king@canonical.com (mailing list archive)
State New, archived
Headers show
Series [next,V2] rtc: msc313: Fix unintentional sign extension issues with left shift of a u16 | expand

Commit Message

Colin King Sept. 28, 2021, 1:46 p.m. UTC 
From: Colin Ian King <colin.king@canonical.com>

Shifting the u16 value returned by readw by 16 bits to the left
will be promoted to a 32 bit signed int and then sign-extended
to an unsigned long. If the top bit of the readw is set then
the shifted value will be sign extended and the top 32 bits of
the result will be set.

Fixes: be7d9c9161b9 ("rtc: Add support for the MSTAR MSC313 RTC")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
V2: Fix identical issue in msc313_rtc_read_time too. Thanks to Daniel Palmer
    for noticing this ommission.
---
 drivers/rtc/rtc-msc313.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Romain Perier Sept. 28, 2021, 5:35 p.m. UTC | #1 
Hi,


Re-tested with rtctest and rtc-range, everything passed.



Le mar. 28 sept. 2021 à 15:46, Colin King <colin.king@canonical.com> a écrit :
>
> From: Colin Ian King <colin.king@canonical.com>
>
> Shifting the u16 value returned by readw by 16 bits to the left
> will be promoted to a 32 bit signed int and then sign-extended
> to an unsigned long. If the top bit of the readw is set then
> the shifted value will be sign extended and the top 32 bits of
> the result will be set.
>
> Fixes: be7d9c9161b9 ("rtc: Add support for the MSTAR MSC313 RTC")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>

Reviewed-by: Romain Perier <romain.perier@gmail.com>

Thanks,
Romain

> ---
> V2: Fix identical issue in msc313_rtc_read_time too. Thanks to Daniel Palmer
>     for noticing this ommission.
> ---
>  drivers/rtc/rtc-msc313.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/rtc/rtc-msc313.c b/drivers/rtc/rtc-msc313.c
> index 5f178d29cfd8..f3fde013c4b8 100644
> --- a/drivers/rtc/rtc-msc313.c
> +++ b/drivers/rtc/rtc-msc313.c
> @@ -53,7 +53,7 @@ static int msc313_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
>         unsigned long seconds;
>
>         seconds = readw(priv->rtc_base + REG_RTC_MATCH_VAL_L)
> -                       | (readw(priv->rtc_base + REG_RTC_MATCH_VAL_H) << 16);
> +                       | ((unsigned long)readw(priv->rtc_base + REG_RTC_MATCH_VAL_H) << 16);
>
>         rtc_time64_to_tm(seconds, &alarm->time);
>
> @@ -122,7 +122,7 @@ static int msc313_rtc_read_time(struct device *dev, struct rtc_time *tm)
>                 udelay(1);
>
>         seconds = readw(priv->rtc_base + REG_RTC_CNT_VAL_L)
> -                       | (readw(priv->rtc_base + REG_RTC_CNT_VAL_H) << 16);
> +                       | ((unsigned long)readw(priv->rtc_base + REG_RTC_CNT_VAL_H) << 16);
>
>         rtc_time64_to_tm(seconds, tm);
>
> --
> 2.32.0
>
Alexandre Belloni Oct. 1, 2021, 9:29 p.m. UTC | #2 
On Tue, 28 Sep 2021 14:46:54 +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> Shifting the u16 value returned by readw by 16 bits to the left
> will be promoted to a 32 bit signed int and then sign-extended
> to an unsigned long. If the top bit of the readw is set then
> the shifted value will be sign extended and the top 32 bits of
> the result will be set.
> 
> [...]

Applied, thanks!

[1/1] rtc: msc313: Fix unintentional sign extension issues with left shift of a u16
      commit: f3606687b447c41d28a011c98373b62b1cd52345

Best regards,
diff mbox series

Patch

diff --git a/drivers/rtc/rtc-msc313.c b/drivers/rtc/rtc-msc313.c
index 5f178d29cfd8..f3fde013c4b8 100644
--- a/drivers/rtc/rtc-msc313.c
+++ b/drivers/rtc/rtc-msc313.c
@@ -53,7 +53,7 @@  static int msc313_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
 	unsigned long seconds;
 
 	seconds = readw(priv->rtc_base + REG_RTC_MATCH_VAL_L)
-			| (readw(priv->rtc_base + REG_RTC_MATCH_VAL_H) << 16);
+			| ((unsigned long)readw(priv->rtc_base + REG_RTC_MATCH_VAL_H) << 16);
 
 	rtc_time64_to_tm(seconds, &alarm->time);
 
@@ -122,7 +122,7 @@  static int msc313_rtc_read_time(struct device *dev, struct rtc_time *tm)
 		udelay(1);
 
 	seconds = readw(priv->rtc_base + REG_RTC_CNT_VAL_L)
-			| (readw(priv->rtc_base + REG_RTC_CNT_VAL_H) << 16);
+			| ((unsigned long)readw(priv->rtc_base + REG_RTC_CNT_VAL_H) << 16);
 
 	rtc_time64_to_tm(seconds, tm);