The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: 78a81d88f60ba773cbe890205e1ee67f00502948 Gitweb: https://git.kernel.org/tip/78a81d88f60ba773cbe890205e1ee67f00502948 Author: Joerg Roedel jroedel@suse.de AuthorDate: Wed, 03 Mar 2021 15:17:12 +01:00 Committer: Borislav Petkov bp@suse.de CommitterDate: Mon, 08 Mar 2021 14:22:17 +01:00
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 --- arch/x86/entry/entry_64_compat.S | 2 ++ arch/x86/include/asm/proto.h | 1 + arch/x86/include/asm/ptrace.h | 15 +++++++++++++++ arch/x86/kernel/traps.c | 3 +-- 4 files changed, 19 insertions(+), 2 deletions(-)
diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S index 541fdaf..0051cf5 100644 --- 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 2c35f1c..b6a9d51 100644 --- 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 d8324a2..409f661 100644 --- 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 7f5aec7..ac1874a 100644 --- 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; }