[RFC/PATCH 0/2] Backports CVE-2021-21781 for 4.4 and 4.9

Hi,

This is a patch series to CVE-2021-21781.
The patch 9c698bff66ab ("RM: ensure the signal page contains defined
contents") depepds on memset32. However, this function is not provided
in 4.4 and 4.9. Therefore, we need the patch 3b3c4babd898 ("lib/string.c:
add multibyte memset functions") to apply this feature.
Another option is to implement only the memset32 function in
arch/arm/kernel/signal.c only or using loop memset, but for simplicity
we have taken the way of applying the original patch 3b3c4babd898
("lib/string.c: add multibyte memset functions") that provides memset32
in mainline kernel.

Best regards,
     Nobuhiro

Matthew Wilcox (1):
  lib/string.c: add multibyte memset functions

Russell King (1):
  ARM: ensure the signal page contains defined contents

 arch/arm/kernel/signal.c | 14 +++++----
 include/linux/string.h   | 30 ++++++++++++++++++
 lib/string.c             | 66 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 104 insertions(+), 6 deletions(-)

-- 
2.32.0

From 97cc3a4817c982954ff69355d2577a92bddbad4a Mon Sep 17 00:00:00 2001
From: Nobuhiro Iwamatsu <redacted>
Date: Fri, 30 Jul 2021 14:40:55 +0900
Subject: [RFC/PATCH 0/2] Backports CVE-2021-21781 for 4.4 and 4.9

Hi,

This is a patch series to CVE-2021-21781.
The patch 9c698bff66ab ("RM: ensure the signal page contains defined
contents") depepds on memset32. However, this function is not provided
in 4.4 and 4.9. Therefore, we need the patch 3b3c4babd898 ("lib/string.c:
add multibyte memset functions") to apply this feature.
Another option is to implement only the memset32 function in
arch/arm/kernel/signal.c only, but for simplicity we have taken the
way of applying the original patch 3b3c4babd898 ("lib/string.c: add
multibyte memset functions") that provides memset32 in mainline kernel.

Best regards,
     Nobuhiro

Matthew Wilcox (1):
  lib/string.c: add multibyte memset functions

Russell King (1):
  ARM: ensure the signal page contains defined contents

 arch/arm/kernel/signal.c | 23 ++++++++++----
 include/linux/string.h   | 30 ++++++++++++++++++
 lib/string.c             | 66 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 113 insertions(+), 6 deletions(-)

-- 
2.32.0