x86/fault: Document the locking in the fault_signal_pending() path

If fault_signal_pending() returns true, then the core mm has unlocked the
mm for us.  Add a comment to help future readers of this code.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/c56de3d103f40e6304437b150aa7b215530d23f7.1612924255.git.luto@kernel.org

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 3ffed00..013910b 100644 (file)
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1380,8 +1380,11 @@ good_area:
         */
        fault = handle_mm_fault(vma, address, flags, regs);
 
-       /* Quick path to respond to signals */
        if (fault_signal_pending(fault, regs)) {
+               /*
+                * Quick path to respond to signals.  The core mm code
+                * has unlocked the mm for us if we get here.
+                */
                if (!user_mode(regs))
                        no_context(regs, error_code, address, SIGBUS,
                                   BUS_ADRERR);