[tip: x86/mm] x86/fault: Document the locking in the fault_signal_pending() path

[tip-bot2 for Andy Lutomirski]

The following commit has been merged into the x86/mm branch of tip:

Commit-ID:     ef2544fb3f6457b79fc73cea39dafd67ee0f2824
Gitweb:        https://git.kernel.org/tip/ef2544fb3f6457b79fc73cea39dafd67ee0f2824
Author:        Andy Lutomirski <luto@xxxxxxxxxx>
AuthorDate:    Tue, 09 Feb 2021 18:33:37 -08:00
Committer:     Borislav Petkov <bp@xxxxxxx>
CommitterDate: Wed, 10 Feb 2021 14:12:07 +01:00

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@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Link: https://lkml.kernel.org/r/c56de3d103f40e6304437b150aa7b215530d23f7.1612924255.git.luto@xxxxxxxxxx
---
 arch/x86/mm/fault.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 3ffed00..013910b 100644
--- 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);