linux-kernel - [PATCH] x86/hyperv: Remove hv_vtl_early

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Date:   Tue, 19 Sep 2023 21:52:32 -0700
From:   Saurabh Sengar <ssengar@...ux.microsoft.com>
To:     kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
        decui@...rosoft.com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org, mikelley@...rosoft.com
Cc:     minipli@...ecurity.net, ssengar@...rosoft.com
Subject: [PATCH] x86/hyperv: Remove hv_vtl_early_init initcall

There has been cases reported where HYPERV_VTL_MODE is enabled by mistake,
on a non Hyper-V platforms. This causes the hv_vtl_early_init function to
be called in an non Hyper-V/VTL platforms which results the memory
corruption.

Remove the early_initcall for vhv_vtl_early_init and call it at the end of
hyperv_init to make sure it is never called in a non Hyper-V platform by
mistake.

Reported-by: Mathias Krause <minipli@...ecurity.net>
Closes: https://lore.kernel.org/lkml/40467722-f4ab-19a5-4989-308225b1f9f0@grsecurity.net/
Signed-off-by: Saurabh Sengar <ssengar@...ux.microsoft.com>
---
This patch is dependent on :
https://lore.kernel.org/lkml/1695182675-13405-1-git-send-email-ssengar@linux.microsoft.com/

 arch/x86/hyperv/hv_init.c       | 3 +++
 arch/x86/hyperv/hv_vtl.c        | 3 +--
 arch/x86/include/asm/mshyperv.h | 2 ++
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index f0128fd4031d..608f4fe41fb7 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -610,6 +610,9 @@ void __init hyperv_init(void)
 	/* Find the VTL */
 	ms_hyperv.vtl = get_vtl();
 
+	if (ms_hyperv.vtl > 0) /* non default VTL */
+		hv_vtl_early_init();
+
 	return;
 
 clean_guest_os_id:
diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
index 36a562218010..999f5ac82fe9 100644
--- a/arch/x86/hyperv/hv_vtl.c
+++ b/arch/x86/hyperv/hv_vtl.c
@@ -215,7 +215,7 @@ static int hv_vtl_wakeup_secondary_cpu(int apicid, unsigned long start_eip)
 	return hv_vtl_bringup_vcpu(vp_id, start_eip);
 }
 
-static int __init hv_vtl_early_init(void)
+int __init hv_vtl_early_init(void)
 {
 	/*
 	 * `boot_cpu_has` returns the runtime feature support,
@@ -230,4 +230,3 @@ static int __init hv_vtl_early_init(void)
 
 	return 0;
 }
-early_initcall(hv_vtl_early_init);
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 033b53f993c6..83019c3aaae9 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -340,8 +340,10 @@ static inline u64 hv_get_non_nested_register(unsigned int reg) { return 0; }
 
 #ifdef CONFIG_HYPERV_VTL_MODE
 void __init hv_vtl_init_platform(void);
+int __init hv_vtl_early_init(void);
 #else
 static inline void __init hv_vtl_init_platform(void) {}
+static int __init hv_vtl_early_init(void) {}
 #endif
 
 #include <asm-generic/mshyperv.h>
-- 
2.34.1