linux-kernel - [PATCH v2] x86/CPU/AMD: Ignore invalid reset reason value

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-next>] [day] [month] [year] [list]

Message-ID: <20250723200752.2851345-1-yazen.ghannam@amd.com>
Date: Wed, 23 Jul 2025 20:07:52 +0000
From: Yazen Ghannam <yazen.ghannam@....com>
To: <x86@...nel.org>
CC: <linux-kernel@...r.kernel.org>, Yazen Ghannam <yazen.ghannam@....com>,
	Libing He <libhe@...hat.com>, Mario Limonciello <mario.limonciello@....com>,
	David Arcari <darcari@...hat.com>
Subject: [PATCH v2] x86/CPU/AMD: Ignore invalid reset reason value

The reset reason value may be "all bits set", e.g. 0xFFFFFFFF. This is a
commonly used error response from hardware. This may occur due to a real
hardware issue or when running in a VM.

The user will see all reset reasons reported in this case.

Return early if running in a VM as this register is not emulated.

Check for an error response value and return early to avoid decoding
invalid data.

Also, adjust the data variable type to match the hardware register size.

Fixes: ab8131028710 ("x86/CPU/AMD: Print the reason for the last reset")
Reported-by: Libing He <libhe@...hat.com>
Signed-off-by: Yazen Ghannam <yazen.ghannam@....com>
Reviewed-by: Mario Limonciello <mario.limonciello@....com>
Cc: David Arcari <darcari@...hat.com>
Cc: stable@...r.kernel.org
---
Link:
https://lore.kernel.org/r/20250721181155.3536023-1-yazen.ghannam@amd.com

v1->v2:
* Include Reviewed-by tag from Mario.
* Include hypervisor check suggested by Boris.

 arch/x86/kernel/cpu/amd.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 50f88fe51816..7a10fe426104 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -1274,10 +1274,13 @@ static const char * const s5_reset_reason_txt[] = {
 
 static __init int print_s5_reset_status_mmio(void)
 {
-	unsigned long value;
 	void __iomem *addr;
+	u32 value;
 	int i;
 
+	if (cpu_feature_enabled(X86_FEATURE_HYPERVISOR))
+		return 0;
+
 	if (!cpu_feature_enabled(X86_FEATURE_ZEN))
 		return 0;
 
@@ -1288,12 +1291,16 @@ static __init int print_s5_reset_status_mmio(void)
 	value = ioread32(addr);
 	iounmap(addr);
 
+	/* Value with "all bits set" is an error response and should be ignored. */
+	if (value == U32_MAX)
+		return 0;
+
 	for (i = 0; i < ARRAY_SIZE(s5_reset_reason_txt); i++) {
 		if (!(value & BIT(i)))
 			continue;
 
 		if (s5_reset_reason_txt[i]) {
-			pr_info("x86/amd: Previous system reset reason [0x%08lx]: %s\n",
+			pr_info("x86/amd: Previous system reset reason [0x%08x]: %s\n",
 				value, s5_reset_reason_txt[i]);
 		}
 	}

base-commit: 65f55a30176662ee37fe18b47430ee30b57bfc98
-- 
2.50.1