2024-04-21 19:17:41

by Borislav Petkov

Subject: [PATCH] x86/cpu: Fix check for RDPKRU in __show_regs()

From: David Kaplan <[email protected]>

cpu_feature_enabled(X86_FEATURE_OSPKE) does not necessarily reflect
whether CR4.PKE is set on the CPU. In particular, they may differ on
non-BSP CPUs before setup_pku() is executed. In this scenario, RDPKRU
will #UD causing the system to hang.

Fix by checking CR4 for PKE enablement which is always correct for the
current CPU.

The scenario happens by inserting a WARN* before setup_pku() in
identiy_cpu() or some other diagnostic which would lead to calling
__show_regs().

[ bp: Massage commit message. ]

Signed-off-by: David Kaplan <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
---
arch/x86/kernel/process_64.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 7062b84dd467..6d3d20e3e43a 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -139,7 +139,7 @@ void __show_regs(struct pt_regs *regs, enum show_regs_mode mode,
log_lvl, d3, d6, d7);
}

- if (cpu_feature_enabled(X86_FEATURE_OSPKE))
+ if (cr4 & X86_CR4_PKE)
printk("%sPKRU: %08x\n", log_lvl, read_pkru());
}

--
2.43.0

2024-04-24 12:43:31

by tip-bot2 for Alexey Makhalov

Subject: [tip: x86/urgent] x86/cpu: Fix check for RDPKRU in __show_regs()

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID: b53c6bd5d271d023857174b8fd3e32f98ae51372
Gitweb: https://git.kernel.org/tip/b53c6bd5d271d023857174b8fd3e32f98ae51372
Author: David Kaplan <[email protected]>
AuthorDate: Sun, 21 Apr 2024 21:17:28 +02:00
Committer: Borislav Petkov (AMD) <[email protected]>
CommitterDate: Wed, 24 Apr 2024 14:30:21 +02:00

x86/cpu: Fix check for RDPKRU in __show_regs()

cpu_feature_enabled(X86_FEATURE_OSPKE) does not necessarily reflect
whether CR4.PKE is set on the CPU. In particular, they may differ on
non-BSP CPUs before setup_pku() is executed. In this scenario, RDPKRU
will #UD causing the system to hang.

Fix by checking CR4 for PKE enablement which is always correct for the
current CPU.

The scenario happens by inserting a WARN* before setup_pku() in
identiy_cpu() or some other diagnostic which would lead to calling
__show_regs().

[ bp: Massage commit message. ]

Signed-off-by: David Kaplan <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
arch/x86/kernel/process_64.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 7062b84..6d3d20e 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -139,7 +139,7 @@ void __show_regs(struct pt_regs *regs, enum show_regs_mode mode,
log_lvl, d3, d6, d7);
}

- if (cpu_feature_enabled(X86_FEATURE_OSPKE))
+ if (cr4 & X86_CR4_PKE)
printk("%sPKRU: %08x\n", log_lvl, read_pkru());
}