Commit 78a81d88 authored by Joerg Roedel's avatar Joerg Roedel Committed by Borislav Petkov
Browse files

x86/sev-es: Introduce ip_within_syscall_gap() helper 



Introduce a helper to check whether an exception came from the syscall
gap and use it in the SEV-ES code. Extend the check to also cover the
compatibility SYSCALL entry path.

Fixes: 315562c9 ("x86/sev-es: Adjust #VC IST Stack on entering NMI handler")
Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Cc: stable@vger.kernel.org # 5.10+
Link: https://lkml.kernel.org/r/20210303141716.29223-2-joro@8bytes.org
parent 5d5675df

arch/x86/entry/entry_64_compat.S

+2 −0
Original line number Diff line number Diff line
@@ -210,6 +210,8 @@ SYM_CODE_START(entry_SYSCALL_compat) 
	/* Switch to the kernel stack */

	movq	PER_CPU_VAR(cpu_current_top_of_stack), %rsp



SYM_INNER_LABEL(entry_SYSCALL_compat_safe_stack, SYM_L_GLOBAL)



	/* Construct struct pt_regs on stack */

	pushq	$__USER32_DS		/* pt_regs->ss */

	pushq	%r8			/* pt_regs->sp */

arch/x86/include/asm/proto.h

+1 −0
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ void __end_SYSENTER_singlestep_region(void); 
void entry_SYSENTER_compat(void);

void __end_entry_SYSENTER_compat(void);

void entry_SYSCALL_compat(void);

void entry_SYSCALL_compat_safe_stack(void);

void entry_INT80_compat(void);

#ifdef CONFIG_XEN_PV

void xen_entry_INT80_compat(void);

arch/x86/include/asm/ptrace.h

+15 −0
Original line number Diff line number Diff line
@@ -94,6 +94,8 @@ struct pt_regs { 
#include <asm/paravirt_types.h>

#endif



#include <asm/proto.h>



struct cpuinfo_x86;

struct task_struct;
@@ -175,6 +177,19 @@ static inline bool any_64bit_mode(struct pt_regs *regs) 
#ifdef CONFIG_X86_64

#define current_user_stack_pointer()	current_pt_regs()->sp

#define compat_user_stack_pointer()	current_pt_regs()->sp



static inline bool ip_within_syscall_gap(struct pt_regs *regs)

{

	bool ret = (regs->ip >= (unsigned long)entry_SYSCALL_64 &&

		    regs->ip <  (unsigned long)entry_SYSCALL_64_safe_stack);



#ifdef CONFIG_IA32_EMULATION

	ret = ret || (regs->ip >= (unsigned long)entry_SYSCALL_compat &&

		      regs->ip <  (unsigned long)entry_SYSCALL_compat_safe_stack);

#endif



	return ret;

}

#endif



static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)

arch/x86/kernel/traps.c

+1 −2
Original line number Diff line number Diff line
@@ -694,8 +694,7 @@ asmlinkage __visible noinstr struct pt_regs *vc_switch_off_ist(struct pt_regs *r 
	 * In the SYSCALL entry path the RSP value comes from user-space - don't

	 * trust it and switch to the current kernel stack

	 */

	if (regs->ip >= (unsigned long)entry_SYSCALL_64 &&

	    regs->ip <  (unsigned long)entry_SYSCALL_64_safe_stack) {

	if (ip_within_syscall_gap(regs)) {

		sp = this_cpu_read(cpu_current_top_of_stack);

		goto sync;

	}