Re: [PATCH] arm64: errata: Add missing sentinels to Spectre-BHB MIDR arrays

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, May 01, 2025 at 11:47:47AM +0100, Will Deacon wrote:
> Commit a5951389e58d ("arm64: errata: Add newer ARM cores to the
> spectre_bhb_loop_affected() lists") added some additional CPUs to the
> Spectre-BHB workaround, including some new arrays for designs that
> require new 'k' values for the workaround to be effective.
> 
> Unfortunately, the new arrays omitted the sentinel entry and so
> is_midr_in_range_list() will walk off the end when it doesn't find a
> match. With UBSAN enabled, this leads to a crash during boot when
> is_midr_in_range_list() is inlined (which was more common prior to
> c8c2647e69be ("arm64: Make  _midr_in_range_list() an exported
> function")):
> 
>  |  Internal error: aarch64 BRK: 00000000f2000001 [#1] PREEMPT SMP
>  |  pstate: 804000c5 (Nzcv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>  |  pc : spectre_bhb_loop_affected+0x28/0x30
>  |  lr : is_spectre_bhb_affected+0x170/0x190
>  | [...]
>  |  Call trace:
>  |   spectre_bhb_loop_affected+0x28/0x30
>  |   update_cpu_capabilities+0xc0/0x184
>  |   init_cpu_features+0x188/0x1a4
>  |   cpuinfo_store_boot_cpu+0x4c/0x60
>  |   smp_prepare_boot_cpu+0x38/0x54
>  |   start_kernel+0x8c/0x478
>  |   __primary_switched+0xc8/0xd4
>  |  Code: 6b09011f 54000061 52801080 d65f03c0 (d4200020)
>  |  ---[ end trace 0000000000000000 ]---
>  |  Kernel panic - not syncing: aarch64 BRK: Fatal exception
> 
> Add the missing sentinel entries.
> 
> Cc: Lee Jones <lee@kernel.org>
> Cc: James Morse <james.morse@arm.com>
> Cc: Doug Anderson <dianders@chromium.org>
> Cc: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Reported-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Fixes: a5951389e58d ("arm64: errata: Add newer ARM cores to the spectre_bhb_loop_affected() lists")
> Signed-off-by: Will Deacon <will@kernel.org>
> ---
>  arch/arm64/kernel/proton-pack.c | 2 ++
>  1 file changed, 2 insertions(+)


Cc: stable <stable@kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>