linux-kernel - Re: [PATCH] arm64: proton-pack: Fix hard lockup when !MITIGATE_SPECTRE_BRANCH

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <06138434-97a3-4363-925a-73b084524131@linaro.org>
Date: Thu, 27 Nov 2025 03:08:47 +0200
From: Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>
To: Jonathan Marek <jonathan@...ek.ca>, Will Deacon <will@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>,
 James Morse <james.morse@....com>, Douglas Anderson <dianders@...omium.org>,
 Trilok Soni <quic_tsoni@...cinc.com>, shechenglong
 <shechenglong@...sion.com>,
 Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
 Shameer Kolothum <skolothumtho@...dia.com>,
 linux-arm-kernel@...ts.infradead.org,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: proton-pack: Fix hard lockup when
 !MITIGATE_SPECTRE_BRANCH_HISTORY

On 11/17/25 07:12, Jonathan Marek wrote:
> The "drop print" commit removed the whole branch and not just the print.
> For some ARM64 cpus, this leads to hard lockup when
> CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY is not enabled.
> 
> Fixes: 62e72463ca71 ("arm64: proton-pack: Drop print when !CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY")
> ---
>   arch/arm64/kernel/proton-pack.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/kernel/proton-pack.c b/arch/arm64/kernel/proton-pack.c
> index c7d70d04c164c..80a580e019c50 100644
> --- a/arch/arm64/kernel/proton-pack.c
> +++ b/arch/arm64/kernel/proton-pack.c
> @@ -1032,6 +1032,8 @@ void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *entry)
>   
>   	if (arm64_get_spectre_v2_state() == SPECTRE_VULNERABLE) {
>   		/* No point mitigating Spectre-BHB alone. */
> +	} else if (!IS_ENABLED(CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY)) {
> +		/* Do nothing */
>   	} else if (supports_ecbhb(SCOPE_LOCAL_CPU)) {
>   		state = SPECTRE_MITIGATED;
>   		set_bit(BHB_HW, &system_bhb_mitigations);


If CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY is unset, the fix is needed
to boot Linux on Lantronix SM8450-HDK and SM8550-HDK boards, which are
otherwise broken since v6.18-rc6.

Reviewed-by: Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>
Tested-by: Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>

-- 
Best wishes,
Vladimir