linux-kernel - [PATCH][v2] x86/bugs: Fix GDS mitigation select for non-ARCH_CAP_GDS

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>] [day] [month] [year] [list]

Message-ID: <20250816001905.2270-1-lirongqing@baidu.com>
Date: Sat, 16 Aug 2025 08:19:05 +0800
From: lirongqing <lirongqing@...du.com>
To: <tglx@...utronix.de>, <bp@...en8.de>, <peterz@...radead.org>,
	<jpoimboe@...nel.org>, <pawan.kumar.gupta@...ux.intel.com>,
	<mingo@...hat.com>, <dave.hansen@...ux.intel.com>, <x86@...nel.org>,
	<hpa@...or.com>, <david.kaplan@....com>, <linux-kernel@...r.kernel.org>
CC: Li RongQing <lirongqing@...du.com>
Subject: [PATCH][v2] x86/bugs: Fix GDS mitigation select for non-ARCH_CAP_GDS_CTRL CPUs

From: Li RongQing <lirongqing@...du.com>

The current GDS mitigation logic incorrectly returns early when
ARCH_CAP_GDS_CTRL is not present, which leads to two problems:

1. CPUs without ARCH_CAP_GDS_CTRL support are incorrectly marked with
   GDS_MITIGATION_OFF when they should be marked as
   GDS_MITIGATION_UCODE_NEEDED.

2. The mitigation state checks and locking verification that follow are
   skipped, which means:
   - fail to detect if the mitigation was locked
   - miss the warning when trying to disable a locked mitigation

Remove the early return to ensure proper mitigation state handling. This
allows:
- Proper mitigation classification for non-ARCH_CAP_GDS_CTRL CPUs
- Complete mitigation state verification

The change fixes the following runtime issues observed:

[    2.809147] unchecked MSR access error: WRMSR to 0x123 (tried to write 0x0000000000000010) at rIP: 0xffffffffb34527b8 (update_gds_msr+0x38/0xe0)
[    2.809147] Call Trace:
[    2.809147]  <TASK>
[    2.809147]  identify_secondary_cpu+0x72/0x90
[    2.809147]  start_secondary+0x7a/0x140
[    2.809147]  common_startup_64+0x13e/0x141
[    2.809147]  </TASK>
[    2.809147] ------------[ cut here ]------------
[    2.809147] WARNING: CPU: 1 PID: 0 at arch/x86/kernel/cpu/bugs.c:1053 update_gds_msr+0x9b/0xe0

Fixes: 8c7261abcb7ad ("x86/bugs: Add attack vector controls for GDS")
Suggested-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
Signed-off-by: Li RongQing <lirongqing@...du.com>
---
 arch/x86/kernel/cpu/bugs.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index b74bf93..9e0b9bf 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1071,7 +1071,6 @@ static void __init gds_select_mitigation(void)
 			gds_mitigation = GDS_MITIGATION_FULL;
 		else {
 			gds_mitigation = GDS_MITIGATION_OFF;
-			return;
 		}
 	}
 
-- 
2.9.4