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x86/xen: remove hypercall page

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commit 7fa0da5373685e7ed249af3fa317ab1e1ba8b0a6 upstream.

The hypercall page is no longer needed. It can be removed, as from the
Xen perspective it is optional.

But, from Linux's perspective, it removes naked RET instructions that
escape the speculative protections that Call Depth Tracking and/or
Untrain Ret are trying to achieve.

This is part of XSA-466 / CVE-2024-53241.

Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Juergen Gross
2024-10-17 15:27:31 +02:00
committed by Greg Kroah-Hartman
parent 1a2471af32
commit 4c24703978
5 changed files with 1 additions and 42 deletions
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2
arch/x86/include/asm/xen/hypercall.h
View File

@@ -88,8 +88,6 @@ struct xen_dm_op_buf;
* there aren't more than 5 arguments...)
*/
extern struct { char _entry[32]; } hypercall_page[];
void xen_hypercall_func(void);
DECLARE_STATIC_CALL(xen_hypercall, xen_hypercall_func);

2
arch/x86/xen/enlighten.c
View File

@@ -26,8 +26,6 @@
#include "smp.h"
#include "pmu.h"
EXPORT_SYMBOL_GPL(hypercall_page);
DEFINE_STATIC_CALL(xen_hypercall, xen_hypercall_hvm);
EXPORT_STATIC_CALL_TRAMP(xen_hypercall);

9
arch/x86/xen/enlighten_hvm.c
View File

@@ -108,15 +108,8 @@ static void __init init_hvm_pv_info(void)
/* PVH set up hypercall page in xen_prepare_pvh(). */
if (xen_pvh_domain())
pv_info.name = "Xen PVH";
else {
u64 pfn;
uint32_t msr;
else
pv_info.name = "Xen HVM";
msr = cpuid_ebx(base + 2);
pfn = __pa(hypercall_page);
wrmsr_safe(msr, (u32)pfn, (u32)(pfn >> 32));
}
xen_setup_features();

7
arch/x86/xen/enlighten_pvh.c
View File

@@ -27,17 +27,10 @@ EXPORT_SYMBOL_GPL(xen_pvh);
void __init xen_pvh_init(struct boot_params *boot_params)
{
u32 msr;
u64 pfn;
xen_pvh = 1;
xen_domain_type = XEN_HVM_DOMAIN;
xen_start_flags = pvh_start_info.flags;
msr = cpuid_ebx(xen_cpuid_base() + 2);
pfn = __pa(hypercall_page);
wrmsr_safe(msr, (u32)pfn, (u32)(pfn >> 32));
if (xen_initial_domain())
x86_init.oem.arch_setup = xen_add_preferred_consoles;
x86_init.oem.banner = xen_banner;

23
arch/x86/xen/xen-head.S
View File

@@ -22,28 +22,6 @@
#include <xen/interface/xen-mca.h>
#include <asm/xen/interface.h>
.pushsection .noinstr.text, "ax"
.balign PAGE_SIZE
SYM_CODE_START(hypercall_page)
.rept (PAGE_SIZE / 32)
UNWIND_HINT_FUNC
ANNOTATE_NOENDBR
ANNOTATE_UNRET_SAFE
ret
/*
* Xen will write the hypercall page, and sort out ENDBR.
*/
.skip 31, 0xcc
.endr
#define HYPERCALL(n) \
.equ xen_hypercall_##n, hypercall_page + __HYPERVISOR_##n * 32; \
.type xen_hypercall_##n, @function; .size xen_hypercall_##n, 32
#include <asm/xen-hypercalls.h>
#undef HYPERCALL
SYM_CODE_END(hypercall_page)
.popsection
#ifdef CONFIG_XEN_PV
__INIT
SYM_CODE_START(startup_xen)
@@ -176,7 +154,6 @@ SYM_FUNC_END(xen_hypercall_intel)
#ifdef CONFIG_XEN_PV
ELFNOTE(Xen, XEN_ELFNOTE_ENTRY, _ASM_PTR startup_xen)
#endif
ELFNOTE(Xen, XEN_ELFNOTE_HYPERCALL_PAGE, _ASM_PTR hypercall_page)
ELFNOTE(Xen, XEN_ELFNOTE_FEATURES,
.ascii "!writable_page_tables|pae_pgdir_above_4gb")
ELFNOTE(Xen, XEN_ELFNOTE_SUPPORTED_FEATURES,