x86/sev: Mark the code returning to user space as syscall gap

When returning to user space, %rsp is user-controlled value.

If it is a SNP-guest and the hypervisor decides to mess with the
code-page for this path while a CPU is executing it, a potential #VC
could hit in the syscall return path and mislead the #VC handler.

So make ip_within_syscall_gap() return true in this case.

Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Joerg Roedel <jroedel@suse.de>
Link: https://lore.kernel.org/r/20220412124909.10467-1-jiangshanlai@gmail.com

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/x86/include/asm/proto.h b/arch/x86/include/asm/proto.h
index feed36d44d04..f042cfc9938f 100644
--- a/arch/x86/include/asm/proto.h
+++ b/arch/x86/include/asm/proto.h
@@ -13,6 +13,8 @@ void syscall_init(void);
 #ifdef CONFIG_X86_64
 void entry_SYSCALL_64(void);
 void entry_SYSCALL_64_safe_stack(void);
+void entry_SYSRETQ_unsafe_stack(void);
+void entry_SYSRETQ_end(void);
 long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2);
 #endif
 
@@ -28,6 +30,8 @@ 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_SYSRETL_compat_unsafe_stack(void);
+void entry_SYSRETL_compat_end(void);
 void entry_INT80_compat(void);
 #ifdef CONFIG_XEN_PV
 void xen_entry_INT80_compat(void);