Re: [PATCH] riscv: lib: Fix address overflow due to large count values in strnlen ZBB path

[Aurelien Jarno <aurelien@aurel32.net>]

Hi,

On 2026-08-19 16:18, gao.rui@zte.com.cn wrote:
> Hi all,
> 
> This patch fixes an issue in the RISC-V ZBB optimized strnlen implementation.
> 
> Problem description: When using the ZBB optimized strnlen implementation, passing very large count values (such as SIZE_MAX) can cause address overflow and return incorrect results.
> 
> This issue was observed in device-mapper tests:
> 
> sh-5.2# dmsetup create testname9 --table "0 8 zero"
> sh-5.2# cat /sys/block/dm-*/dm/name
> testname
> sh-5.2# dmsetup remove testname9
> 
> The overflow in strnlen caused failures in string handling during device-mapper operations.
> 
> Patch summary:
> - Explicitly introduce the strnlen_generic label.
> - Simplify the generic implementation loop.

This part should be in a separate patch, separated from the bug fix, and 
if possible with some benchmark.

> - Add fallback logic in strnlen_zbb to redirect to the generic path when a0 + a1 overflows.
> This ensures correct behavior for large count values and SIZE_MAX cases.

Is there a way to instead to fix the strnlen_zbb to avoid the fallback?

Regards
Aurelien

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                     http://aurel32.net