This is a note to let you know that I've just added the patch titled
xtensa: fix uaccess-related livelock in do_page_fault
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xtensa-fix-uaccess-related-livelock-in-do_page_fault.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7b9acbb6aad4f54623dcd4bd4b1a60fe0c727b09 Mon Sep 17 00:00:00 2001
From: Max Filippov <jcmvbkbc@xxxxxxxxx>
Date: Sun, 7 Feb 2021 04:57:58 -0800
Subject: xtensa: fix uaccess-related livelock in do_page_fault
From: Max Filippov <jcmvbkbc@xxxxxxxxx>
commit 7b9acbb6aad4f54623dcd4bd4b1a60fe0c727b09 upstream.
If a uaccess (e.g. get_user()) triggers a fault and there's a
fault signal pending, the handler will return to the uaccess without
having performed a uaccess fault fixup, and so the CPU will immediately
execute the uaccess instruction again, whereupon it will livelock
bouncing between that instruction and the fault handler.
https://lore.kernel.org/lkml/20210121123140.GD48431@C02TD0UTHF1T.local/
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Max Filippov <jcmvbkbc@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/xtensa/mm/fault.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/arch/xtensa/mm/fault.c
+++ b/arch/xtensa/mm/fault.c
@@ -112,8 +112,11 @@ good_area:
*/
fault = handle_mm_fault(vma, address, flags, regs);
- if (fault_signal_pending(fault, regs))
+ if (fault_signal_pending(fault, regs)) {
+ if (!user_mode(regs))
+ goto bad_page_fault;
return;
+ }
if (unlikely(fault & VM_FAULT_ERROR)) {
if (fault & VM_FAULT_OOM)
Patches currently in stable-queue which might be from jcmvbkbc@xxxxxxxxx are
queue-5.10/xtensa-move-coprocessor_flush-to-the-.text-section.patch
queue-5.10/xtensa-fix-uaccess-related-livelock-in-do_page_fault.patch
