linux-kernel - Re: [PATCH] scsi: arcmsr: avoid do

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Date:   Mon, 22 Jan 2018 19:06:10 +0800
From:   Ching Huang <ching2048@...ca.com.tw>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        y2038@...ts.linaro.org, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: arcmsr: avoid do_gettimeofday

On Mon, 2018-01-22 at 00:12 +0100, Arnd Bergmann wrote:
> The arcmsr uses its own implementation of time_to_tm(), along with do_gettimeofday()
> to read the current time. While the algoritm used here is fine in principle, it
> suffers from two problems:
> 
> - it assigns the seconds portion of the timeval to a 32-bit unsigned integer that
>   overflows in 2106 even on 64-bit architectures.
> - do_gettimeofday() returns a time_t that overflows in 2038 on all 32-bit systems.
> 
> This changes the time retrieval function to ktime_get_real_seconds(), which returns
> a proper 64-bit value, and replaces the open-coded time_to_tm() algorithm with
> a call to the safe time64_to_tm().
> 
> I checked way all numbers are indexed and found that months are given in range
> 0..11 while the days are in range 1..31, same as 'struct tm', but the year value
> that the firmware expects starts in 2000 while 'struct tm' is based on year 1900,
> so it needs a small adjustment.
> 
> Fixes: b416c099472a ("scsi: arcmsr: Add a function to set date and time to firmware")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/scsi/arcmsr/arcmsr_hba.c | 37 ++++++++++---------------------------
>  1 file changed, 10 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/scsi/arcmsr/arcmsr_hba.c b/drivers/scsi/arcmsr/arcmsr_hba.c
> index 47745592cff4..75e828bd30e3 100644
> --- a/drivers/scsi/arcmsr/arcmsr_hba.c
> +++ b/drivers/scsi/arcmsr/arcmsr_hba.c
> @@ -3489,8 +3489,9 @@ static int arcmsr_polling_ccbdone(struct AdapterControlBlock *acb,
>  static void arcmsr_set_iop_datetime(struct timer_list *t)
>  {
>  	struct AdapterControlBlock *pacb = from_timer(pacb, t, refresh_timer);
> -	unsigned int days, j, i, a, b, c, d, e, m, year, mon, day, hour, min, sec, secs, next_time;
> -	struct timeval tv;
> +	unsigned int next_time;
> +	struct tm tm;
> +
>  	union {
>  		struct	{
>  		uint16_t	signature;
> @@ -3506,33 +3507,15 @@ static void arcmsr_set_iop_datetime(struct timer_list *t)
>  		} b;
>  	} datetime;
>  
> -	do_gettimeofday(&tv);
> -	secs = (u32)(tv.tv_sec - (sys_tz.tz_minuteswest * 60));
> -	days = secs / 86400;
> -	secs = secs - 86400 * days;
> -	j = days / 146097;
> -	i = days - 146097 * j;
> -	a = i + 719468;
> -	b = ( 4 * a + 3 ) / 146097;
> -	c = a - ( 146097 * b ) / 4;
> -	d = ( 4 * c + 3 ) / 1461 ;
> -	e = c - ( 1461 * d ) / 4 ;
> -	m = ( 5 * e + 2 ) / 153 ;
> -	year = 400 * j + 100 * b + d + m / 10 - 2000;
> -	mon = m + 3 - 12 * ( m /10 );
> -	day = e - ( 153 * m + 2 ) / 5 + 1;
> -	hour = secs / 3600;
> -	secs = secs - 3600 * hour;
> -	min = secs / 60;
> -	sec = secs - 60 * min;
> +	time64_to_tm(ktime_get_real_seconds(), -sys_tz.tz_minuteswest * 60, &tm);
>  
>  	datetime.a.signature = 0x55AA;
> -	datetime.a.year = year;
> -	datetime.a.month = mon;
> -	datetime.a.date = day;
> -	datetime.a.hour = hour;
> -	datetime.a.minute = min;
> -	datetime.a.second = sec;
> +	datetime.a.year = tm.tm_year - 100; /* base 2000 instead of 1900 */
> +	datetime.a.month = tm.tm_mon;
> +	datetime.a.date = tm.tm_mday;
> +	datetime.a.hour = tm.tm_hour;
> +	datetime.a.minute = tm.tm_min;
> +	datetime.a.second = tm.tm_sec;
>  
>  	switch (pacb->adapter_type) {
>  		case ACB_ADAPTER_TYPE_A: {

This patch works on kernel 4.14.0, thanks Arnd.