4.9-stable review patch. If anyone has any objections, please let me know.
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From: Colin Ian King colin.king@canonical.com
[ Upstream commit 347876ad47b9923ce26e686173bbf46581802ffa ]
The shifting of buf[5] by 24 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 buf[5] is set then all then all the upper bits sec end up as also being set because of the sign-extension. Fix this by casting buf[5] to an unsigned long before the shift.
Detected by CoverityScan, CID#1465292 ("Unintended sign extension")
Fixes: 0e1492330cd2 ("rtc: add rtc-tx4939 driver") Signed-off-by: Colin Ian King colin.king@canonical.com Signed-off-by: Alexandre Belloni alexandre.belloni@bootlin.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/rtc/rtc-tx4939.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
--- a/drivers/rtc/rtc-tx4939.c +++ b/drivers/rtc/rtc-tx4939.c @@ -86,7 +86,8 @@ static int tx4939_rtc_read_time(struct d for (i = 2; i < 6; i++) buf[i] = __raw_readl(&rtcreg->dat); spin_unlock_irq(&pdata->lock); - sec = (buf[5] << 24) | (buf[4] << 16) | (buf[3] << 8) | buf[2]; + sec = ((unsigned long)buf[5] << 24) | (buf[4] << 16) | + (buf[3] << 8) | buf[2]; rtc_time_to_tm(sec, tm); return rtc_valid_tm(tm); } @@ -147,7 +148,8 @@ static int tx4939_rtc_read_alarm(struct alrm->enabled = (ctl & TX4939_RTCCTL_ALME) ? 1 : 0; alrm->pending = (ctl & TX4939_RTCCTL_ALMD) ? 1 : 0; spin_unlock_irq(&pdata->lock); - sec = (buf[5] << 24) | (buf[4] << 16) | (buf[3] << 8) | buf[2]; + sec = ((unsigned long)buf[5] << 24) | (buf[4] << 16) | + (buf[3] << 8) | buf[2]; rtc_time_to_tm(sec, &alrm->time); return rtc_valid_tm(&alrm->time); }