5.15-stable review patch. If anyone has any objections, please let me know.
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From: Juergen Gross jgross@suse.com
commit a2796dff62d6c6bfc5fbebdf2bee0d5ac0438906 upstream.
Instead of jumping to the Xen hypercall page for doing the iret hypercall, directly code the required sequence in xen-asm.S.
This is done in preparation of no longer using hypercall page at all, as it has shown to cause problems with speculation mitigations.
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: Jan Beulich jbeulich@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/xen/xen-asm.S | 27 ++++++++++++++++++--------- 1 file changed, 18 insertions(+), 9 deletions(-)
--- a/arch/x86/xen/xen-asm.S +++ b/arch/x86/xen/xen-asm.S @@ -170,7 +170,6 @@ SYM_CODE_START(xen_early_idt_handler_arr SYM_CODE_END(xen_early_idt_handler_array) __FINIT
-hypercall_iret = hypercall_page + __HYPERVISOR_iret * 32 /* * Xen64 iret frame: * @@ -180,16 +179,27 @@ hypercall_iret = hypercall_page + __HYPE * cs * rip <-- standard iret frame * - * flags + * flags <-- xen_iret must push from here on * - * rcx } - * r11 }<-- pushed by hypercall page - * rsp->rax } + * rcx + * r11 + * rsp->rax */ +.macro xen_hypercall_iret + pushq $0 /* Flags */ + push %rcx + push %r11 + push %rax + mov $__HYPERVISOR_iret, %eax + syscall /* Do the IRET. */ +#ifdef CONFIG_MITIGATION_SLS + int3 +#endif +.endm + SYM_CODE_START(xen_iret) UNWIND_HINT_EMPTY - pushq $0 - jmp hypercall_iret + xen_hypercall_iret SYM_CODE_END(xen_iret)
/* @@ -290,8 +300,7 @@ SYM_CODE_START(xen_entry_SYSENTER_compat UNWIND_HINT_ENTRY lea 16(%rsp), %rsp /* strip %rcx, %r11 */ mov $-ENOSYS, %rax - pushq $0 - jmp hypercall_iret + xen_hypercall_iret SYM_CODE_END(xen_entry_SYSENTER_compat) SYM_CODE_END(xen_entry_SYSCALL_compat)