[PATCH v2] util/grub.d/30_os-prober.in: Fix GRUB_OS_PROBER_SKIP_LIST for non-EFI

[Pascal Hambourg <pascal@plouf.fr.eu.org>]

GRUB documentation states:

‘GRUB_OS_PROBER_SKIP_LIST’
  List of space-separated FS UUIDs of filesystems to be ignored from
  os-prober output. For efi chainloaders it’s <UUID>@<EFI FILE>

But the actual behaviour does not match this description.

  GRUB_OS_PROBER_SKIP_LIST="<UUID>"

does nothing. In order to skip non-EFI bootloaders, you must set

  GRUB_OS_PROBER_SKIP_LIST="<UUID>@<DEVICE>"

which is both absurd (<UUID> and <DEVICE> are redundant) and wrong
(<DEVICE> such as /dev/sd* may not be persistent across boots).

Also, any non-word character is accepted as a separator, including
'-' and '@' which may be present in UUIDs. This can cause false
positives because of partial UUID match.

This patch fixes these flaws while retaining some backward
compatibility with previous behaviour which may be expected by
existing setups:
- also accept <UUID>@/dev/* (with warning) for non-EFI bootloaders
- also accept comma and semicolon as separator

Fixes: 55e706c9 (Add GRUB_OS_PROBER_SKIP_LIST to selectively skipping systems)
Signed-off-by: Pascal Hambourg <pascal@plouf.fr.eu.org>
---
Changes in v2:
- enforce UUID boundaries with correct separators
- warn if @/dev/* is found in GRUB_OS_PROBER_SKIP_LIST
- update documentation
- call grub-probe only when needed

 docs/grub.texi              |  7 +++++--
 util/grub.d/30_os-prober.in | 19 +++++++++++++------
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/docs/grub.texi b/docs/grub.texi
index a225f9a88..594d475fc 100644
--- a/docs/grub.texi
+++ b/docs/grub.texi
@@ -1561,8 +1561,11 @@ this option to @samp{false} to enable this feature in the
 @command{grub-mkconfig} command.
 
 @item GRUB_OS_PROBER_SKIP_LIST
-List of space-separated FS UUIDs of filesystems to be ignored from os-prober
-output. For efi chainloaders it's <UUID>@@<EFI FILE>
+List of space-separated case insensitive UUIDs of filesystems to be ignored
+from os-prober output. For EFI chainloaders it's <UUID>@@<EFI FILE>. For
+backward compatibility with previous behaviour, <UUID>@@/dev/* is also accepted
+for non-EFI chainloaders even if the device does not match, and comma and
+semicolon are also accepted as separator.
 
 @item GRUB_DISABLE_SUBMENU
 Normally, @command{grub-mkconfig} will generate top level menu entry for
diff --git a/util/grub.d/30_os-prober.in b/util/grub.d/30_os-prober.in
index 656301eaf..394747759 100644
--- a/util/grub.d/30_os-prober.in
+++ b/util/grub.d/30_os-prober.in
@@ -117,19 +117,26 @@ if [ "x$GRUB_TOP_LEVEL_OS_PROBER" != x ]; then
   OSPROBED=$(grub_move_to_front "$GRUB_TOP_LEVEL_OS_PROBER" ${OSPROBED})
 fi
 
+case "$GRUB_OS_PROBER_SKIP_LIST" in *@/[dD][eE][vV]/*)
+	grub_warn "$(gettext_printf "GRUB_OS_PROBER_SKIP_LIST contains deprecated <UUID>@/dev/* notation. The @/dev/* suffix is ignored.")"
+esac
+
 for OS in ${OSPROBED} ; do
   DEVICE="`echo ${OS} | cut -d ':' -f 1`"
   LONGNAME="`echo ${OS} | cut -d ':' -f 2 | tr '^' ' '`"
   LABEL="`echo ${OS} | cut -d ':' -f 3 | tr '^' ' '`"
   BOOT="`echo ${OS} | cut -d ':' -f 4`"
-  if UUID="`${grub_probe} --target=fs_uuid --device ${DEVICE%@*}`"; then
-    EXPUUID="$UUID"
+  unset UUID
+  if [ -n "${GRUB_OS_PROBER_SKIP_LIST}" ] && UUID="`${grub_probe} --target=fs_uuid --device ${DEVICE%@*}`"; then
+    SPACE='[[:space:],;]' # regex matching spaces and common separators
 
-    if [ x"${DEVICE#*@}" != x ] ; then
-      EXPUUID="${EXPUUID}@${DEVICE#*@}"
+    if [ x"${DEVICE##*@*}" = x ] ; then
+      EXPUUID="$UUID@${DEVICE#*@}"
+    else
+      EXPUUID="$UUID(@/dev/.*)?"
     fi
 
-    if [ "x${GRUB_OS_PROBER_SKIP_LIST}" != "x" ] && [ "x`echo ${GRUB_OS_PROBER_SKIP_LIST} | grep -i -e '\b'${EXPUUID}'\b'`" != "x" ] ; then
+    if printf %s " ${GRUB_OS_PROBER_SKIP_LIST} " | grep -Eqie "${SPACE}${EXPUUID}${SPACE}" ; then
       echo "Skipped ${LONGNAME} on ${DEVICE} by user request." >&2
       continue
     fi
@@ -299,7 +306,7 @@ EOF
       echo "$title_correction_code"
     ;;
     macosx)
-      if [ "${UUID}" ]; then
+      if [ "${UUID=`${grub_probe} --target=fs_uuid --device ${DEVICE}`}" ]; then
 	OSXUUID="${UUID}"
 	osx_entry xnu_kernel 32
 	osx_entry xnu_kernel64 64
-- 
2.39.2


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