[BUG] ARM64 regression: NULL pointer dereference in arm_smccc_version_init+0x90/0x1ac

[Will Deacon]

On Fri, Jan 24, 2025 at 03:52:10PM +0100, Emanuele Rocca wrote:
> longterm kernel 6.1.123 crashes early when booting on the Lenovo Thinkpad X13s
> with the following error:
> 
>  Unable to handle kernel NULL pointer dereference at virtual address 0000000000000264
> 
>  pc: arm_smccc_version_init+0x90/0x1ac

Please can you share the full crash log?

> According to faddr2line, that is line 31 of smccc.c:
> 
>  arm_smccc_version_init+0x90/0x1ac:
>  arm_smccc_version_init at debian/build/build_arm64_none_arm64/drivers/firmware/smccc/smccc.c:31
> 
>  22 void __init arm_smccc_version_init(u32 version, enum arm_smccc_conduit conduit)
>  23 {
>  24         struct arm_smccc_res res;
>  25 
>  26         smccc_version = version;
>  27         smccc_conduit = conduit;
>  28 
>  29         smccc_trng_available = smccc_probe_trng();
>  30 
>  31         if ((smccc_version >= ARM_SMCCC_VERSION_1_2) &&
> 
> This is with kernel 6.1.123. The last known good kernel I have available right
> now is 6.1.119. In the 6.1.120 changelog I see the following commit which seems
> potentially related?
> 
>  https://lore.kernel.org/all/20241106160448.2712997-1-mark.rutland@arm.com/
> 
> That's stable commit [1].

I can't see anything wrong with that patch but if you have reason to
suspect that it's broken can you try reverting it to see if the problem
disappears?

Will