diff options
| -rw-r--r-- | arch/x86_64/kernel/entry.S | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S index 10ec27b..c946e4f 100644 --- a/arch/x86_64/kernel/entry.S +++ b/arch/x86_64/kernel/entry.S @@ -180,6 +180,10 @@ rff_trace: * * XXX if we had a free scratch register we could save the RSP into the stack frame * and report it properly in ps. Unfortunately we haven't. + * + * When user can change the frames always force IRET. That is because + * it deals with uncanonical addresses better. SYSRET has trouble + * with them due to bugs in both AMD and Intel CPUs. */ ENTRY(system_call) @@ -254,7 +258,10 @@ sysret_signal: xorl %esi,%esi # oldset -> arg2 call ptregscall_common 1: movl $_TIF_NEED_RESCHED,%edi - jmp sysret_check + /* Use IRET because user could have changed frame. This + works because ptregscall_common has called FIXUP_TOP_OF_STACK. */ + cli + jmp int_with_check badsys: movq $-ENOSYS,RAX-ARGOFFSET(%rsp) @@ -280,7 +287,8 @@ tracesys: call syscall_trace_leave RESTORE_TOP_OF_STACK %rbx RESTORE_REST - jmp ret_from_sys_call + /* Use IRET because user could have changed frame */ + jmp int_ret_from_sys_call CFI_ENDPROC /* |