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: 315562c9af3d5 ("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

diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index 541fdaf6404533bd2d2558bd0ebc426324f2c96c..0051cf5c792d1aeccb7800ba4c02b354c24f885c 100644 (file)
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -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 */

diff --git a/arch/x86/include/asm/proto.h b/arch/x86/include/asm/proto.h
index 2c35f1c01a2df103854215bdba3bec992fe2e177..b6a9d51d1d7911894fa6b831b2f01a05f1daf57f 100644 (file)
--- a/arch/x86/include/asm/proto.h
+++ b/arch/x86/include/asm/proto.h
@@ -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);

diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
index d8324a23669610e379078543e3cbed3855aaae3e..409f661481e110c3471b83477a159cae4052b540 100644 (file)
--- a/arch/x86/include/asm/ptrace.h
+++ b/arch/x86/include/asm/ptrace.h
@@ -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)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 7f5aec758f0eeac2d9bcebcd80963bc9d79e7ab3..ac1874a2a70e8cc41654bc652a8922238192a8ff 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -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;
        }