grub2: fix CVE-2021-3981

(From OE-Core rev: f06da194871fec7c4586a9141314f2760292d6d0)

Signed-off-by: Yongxin Liu <yongxin.liu@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit bb554d14142f93c39fd1516a31757006531c348f)
Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-bsp/grub/files/CVE-2021-3981-grub-mkconfig-Restore-umask-for-the-grub.cfg.patch

@@ -0,0 +1,49 @@
+From 0adec29674561034771c13e446069b41ef41e4d4 Mon Sep 17 00:00:00 2001
+From: Michael Chang <mchang@suse.com>
+Date: Fri, 3 Dec 2021 16:13:28 +0800
+Subject: [PATCH] grub-mkconfig: Restore umask for the grub.cfg
+
+The commit ab2e53c8a (grub-mkconfig: Honor a symlink when generating
+configuration by grub-mkconfig) has inadvertently discarded umask for
+creating grub.cfg in the process of running grub-mkconfig. The resulting
+wrong permission (0644) would allow unprivileged users to read GRUB
+configuration file content. This presents a low confidentiality risk
+as grub.cfg may contain non-secured plain-text passwords.
+
+This patch restores the missing umask and sets the creation file mode
+to 0600 preventing unprivileged access.
+
+Fixes: CVE-2021-3981
+
+Signed-off-by: Michael Chang <mchang@suse.com>
+Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
+
+Upstream-Status: Backport
+CVE: CVE-2021-3981
+
+Reference to upstream patch:
+https://git.savannah.gnu.org/cgit/grub.git/commit/?id=0adec29674561034771c13e446069b41ef41e4d4
+
+Signed-off-by: Yongxin Liu <yongxin.liu@windriver.com>
+---
+ util/grub-mkconfig.in | 3 +++
+ 1 file changed, 3 insertions(+)
+
+diff --git a/util/grub-mkconfig.in b/util/grub-mkconfig.in
+index c3ea7612e..62335d027 100644
+--- a/util/grub-mkconfig.in
++++ b/util/grub-mkconfig.in
+@@ -301,7 +301,10 @@ and /etc/grub.d/* files or please file a bug report with
+     exit 1
+   else
+     # none of the children aborted with error, install the new grub.cfg
++    oldumask=$(umask)
++    umask 077
+     cat ${grub_cfg}.new > ${grub_cfg}
++    umask $oldumask
+     rm -f ${grub_cfg}.new
+   fi
+ fi
+-- 
+2.31.1
+

meta/recipes-bsp/grub/grub2.inc

@@ -20,6 +20,7 @@ SRC_URI = "https://alpha.gnu.org/gnu/grub/grub-${REALPV}.tar.xz \
            file://0001-grub.d-10_linux.in-add-oe-s-kernel-name.patch \
            file://determinism.patch \
            file://0001-RISC-V-Restore-the-typcast-to-long.patch \
+           file://CVE-2021-3981-grub-mkconfig-Restore-umask-for-the-grub.cfg.patch \
 "
 
 SRC_URI[sha256sum] = "2c87f1f21e2ab50043e6cd9163c08f1b6c3a6171556bf23ff9ed65b074145484"