File 0001-30_uefi-firmware-fix-printf-format-with-nu... of Package grub2.26023

Overview Repositories Revisions Requests Users Attributes Meta

File 0001-30_uefi-firmware-fix-printf-format-with-null-byte.patch of Package grub2.26023

From 47eddcfc6859f269bb3cfaf95d5b33502cafd9ec Mon Sep 17 00:00:00 2001
From: Michael Chang <mchang@suse.com>
Date: Mon, 21 Jun 2021 05:11:18 +0000
Subject: [PATCH] 30_uefi-firmware: fix printf format with null byte
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

On a Raspberry Pi 4, the OsIndications variable is set as following

$ od -An -t u1 /sys/firmware/efi/efivars/OsIndicationsSupported-8be4df61-93ca-11d2-aa0d-00e098032b8c
 6   0   0   0   0   0   0   0   0   0   0   0

The fifth byte indicates there's no boot to uefi firmware support as no
bit is set. However the /etc/grub.d/30_uefi-firmware mistakenly detects
that from the grub-mkconfig output.

/etc/grub.d/30_uefi-firmware: line 34: warning: command substitution: ignored null byte in input
 Adding boot menu entry for UEFI Firmware Settings ...

The warning has dictated that the null byte is ignored from the printf
input arguments so that the expression of

rintf 0x%x \'"$(cat $OS_INDICATIONS | cut -b5)"\')

becomes

printf 0x%x \'""\'
 0x27

The numeric value of trailing character \' is outputted instead of the
null byte.

From the printf manual, there's description to the synax of formatting
the numeric value ouput of a character.

"If the leading character of a numeric argument is ‘"’ or ‘'’ then its
value is the numeric value of the immediately following character. Any
remaining characters are silently ignored if the POSIXLY_CORRECT
environment variable is set; otherwise, a warning is printed. For
example, ‘printf "%d" "'a"’ outputs ‘97’ on hosts that use the ASCII
character set, since ‘a’ has the numeric value 97 in ASCII."

From the descrption the trailing \' appears to be superfluous and should
get removed to have correct output.

printf 0x%x \'""
 0x0

In additon to suppress the warning message of ignored null byte in
input, we can delete it so an empty string is used.

To illustrate the problem using echo as example

printf 0x%x \'"$(echo -e '\x00')"
 -bash: warning: command substitution: ignored null byte in input
 0x0

And here using tr to delete the null character

printf 0x%x \'"$(echo -e '\x00'| tr -d '\000')"

The expression above is substituted to

printf 0x%x \'""
 0x0

Signed-off-by: Michael Chang <mchang@suse.com>
---
 util/grub.d/30_uefi-firmware.in | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/util/grub.d/30_uefi-firmware.in b/util/grub.d/30_uefi-firmware.in
index d344d3883..d069f2727 100644
--- a/util/grub.d/30_uefi-firmware.in
+++ b/util/grub.d/30_uefi-firmware.in
@@ -31,7 +31,7 @@ EFI_GLOBAL_VARIABLE=8be4df61-93ca-11d2-aa0d-00e098032b8c
 OS_INDICATIONS="$EFI_VARS_DIR/OsIndicationsSupported-$EFI_GLOBAL_VARIABLE"
 
 if [ -e "$OS_INDICATIONS" ] && \
-   [ "$(( $(printf 0x%x \'"$(cat $OS_INDICATIONS | cut -b5)"\') & 1 ))" = 1 ]; then
+   [ "$(( $(printf 0x%x \'"$(cat $OS_INDICATIONS | cut -b5 | tr -d '\000')") & 1 ))" = 1 ]; then
   LABEL="UEFI Firmware Settings"
 
   gettext_printf "Adding boot menu entry for UEFI Firmware Settings ...\n" >&2
-- 
2.26.2

Places

File 0001-30_uefi-firmware-fix-printf-format-with-null-byte.patch of Package grub2.26023

Places