Re: [PATCH 07/12] rtc: rzn1: fix alarm range check truncation on 32-bit systems

[Alexandre Belloni]

On 15/06/2026 16:48:00+0100, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> 
> alarm and farest were declared as unsigned long, but
> rtc_tm_to_time64() returns time64_t (s64). On 32-bit systems where
> unsigned long is 32 bits, the assignment silently truncates the upper
> 32 bits of the timestamp.
> 
> Fix by declaring alarm and farest as time64_t and replacing
> time_after() with a direct signed comparison, which is correct for
> time64_t values that will never realistically overflow.
> 

I'd argue that this is never going to overflow ever as unsigned long
gets you to 2106 which is way past the usable range of the RTC so there
is a trade off between the size you are going to take on the stack and
the actual usefulness of the fix.

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com