[PATCH] cpufreq: sun50i: prevent out-of-bounds access

[Jernej Škrabec]

Dne četrtek, 20. marec 2025 ob 16:55:57 Srednjeevropski standardni čas je Andre Przywara napisal(a):
> A KASAN enabled kernel reports an out-of-bounds access when handling the
> nvmem cell in the sun50i cpufreq driver:
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in sun50i_cpufreq_nvmem_probe+0x180/0x3d4
> Read of size 4 at addr ffff000006bf31e0 by task kworker/u16:1/38
> 
> This is because the DT specifies the nvmem cell as covering only two
> bytes, but we use a u32 pointer to read the value. DTs for other SoCs
> indeed specify 4 bytes, so we cannot just shorten the variable to a u16.
> 
> Fortunately nvmem_cell_read() allows to return the length of the nvmem
> cell, in bytes, so we can use that information to only access the valid
> portion of the data.
> To cover multiple cell sizes, use memcpy() to copy the information into a
> zeroed u32 buffer, then also make sure we always read the data in little
> endian fashion, as this is how the data is stored in the SID efuses.
> 
> Fixes: 6cc4bcceff9a ("cpufreq: sun50i: Refactor speed bin decoding")
> Reported-by: Jernej Skrabec <jernej.skrabec at gmail.com>
> Signed-off-by: Andre Przywara <andre.przywara at arm.com>

Thanks for fixing that!

Reviewed-by: Jernej Škrabec <jernej.skrabec at gmail.com>

Best regards,
Jernej