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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: 315562c9af ("x86/sev-es: Adjust #VC IST Stack on entering NMI handler")
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: stable@vger.kernel.org # 5.10+
Link: https://lkml.kernel.org/r/20210303141716.29223-2-joro@8bytes.org
rM2-mainline
Joerg Roedel 2021-03-03 15:17:12 +01:00 committed by Borislav Petkov
parent 5d5675df79
commit 78a81d88f6
4 changed files with 19 additions and 2 deletions
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2
arch/x86/entry/entry_64_compat.S
View File

@ -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 */

1
arch/x86/include/asm/proto.h
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@ -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);

15
arch/x86/include/asm/ptrace.h
View File

@ -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)

3
arch/x86/kernel/traps.c
View File

@ -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;
}