File util-linux-bsc-1222465.patch of Package util-linux
From 8b8da020f57414c90981371da71fdf32d2253ac7 Mon Sep 17 00:00:00 2001
From: Martin Jungblut Schreiner <martinjungblut@gmail.com>
Date: Mon, 29 Dec 2025 19:52:56 -0300
Subject: [PATCH 1/2] libfdisk: (dos) fix logical partition start
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
fdisk could accept adjacent logical partitions, causing the EBR for the new
logical partition to be written inside the previous partition’s data area.
This can corrupt the EBR chain.
Fix free-sector search to keep an EBR gap (first_lba) after logical partitions.
---
libfdisk/src/dos.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/libfdisk/src/dos.c b/libfdisk/src/dos.c
index c88d2a4f213..f85104b2828 100644
--- a/libfdisk/src/dos.c
+++ b/libfdisk/src/dos.c
@@ -1201,6 +1201,21 @@ static int find_first_free_sector_in_range(
p_start -= cxt->first_lba;
if (first < p_start)
continue;
+
+ /* if we're placing a logical partition start, ensure
+ there's room for the *next* EBR (stored at start - first_lba).
+ therefore enforce:
+ start(Lnew) >= end(Lprev) + first_lba + 1 */
+ if (logical && first > p_end && (first - p_end) <= cxt->first_lba) {
+ first = p_end + 1 + cxt->first_lba;
+ first_moved = 1;
+
+ if (first > end)
+ return -ENOSPC;
+
+ continue;
+ }
+
if (first <= p_end) {
first = p_end + 1 + (logical ? cxt->first_lba : 0);
first_moved = 1;
From bf3d4aeec708fae7aa30530a1bf42ee1d35366f8 Mon Sep 17 00:00:00 2001
From: Martin Jungblut Schreiner <martinjungblut@gmail.com>
Date: Mon, 29 Dec 2025 20:46:39 -0300
Subject: [PATCH 2/2] tests: fdisk: add regression test for missing EBR gap
between logical partitions
Add a DOS/MBR test case where the first logical partition starts at 6145
(extended start 2048). In the regressed behaviour fdisk allows the next
logical partition to start at prev_end+1, which would place its EBR
(start - 2048) inside the previous logical partition.
The expected behaviour is to require the next starting sector to be at least
prev_end + 2048 + 1 (e.g. 790528 in the testcase).
Closes issue #3925.
---
tests/expected/fdisk/mbr-logical-ebr-gap | 15 ++++++++++
tests/ts/fdisk/mbr-logical-ebr-gap | 35 ++++++++++++++++++++++++
2 files changed, 50 insertions(+)
create mode 100644 tests/expected/fdisk/mbr-logical-ebr-gap
create mode 100755 tests/ts/fdisk/mbr-logical-ebr-gap
diff --git a/tests/expected/fdisk/mbr-logical-ebr-gap b/tests/expected/fdisk/mbr-logical-ebr-gap
new file mode 100644
index 00000000000..c25b9be7a8d
--- /dev/null
+++ b/tests/expected/fdisk/mbr-logical-ebr-gap
@@ -0,0 +1,15 @@
+
+---layout----------
+Disk <removed>: 1 GiB, 1073741824 bytes, 2097152 sectors
+Units: sectors of 1 * 512 = 512 bytes
+Sector size (logical/physical): 512 bytes / 512 bytes
+I/O size (minimum/optimal): 512 bytes / <removed> bytes
+Disklabel type: dos
+Disk identifier: <removed>
+
+Device Boot Start End Sectors Id Type Start-C/H/S End-C/H/S Attrs
+<removed>1 2048 2097151 2095104 5 Extended 0/32/33 130/138/8
+<removed>5 6145 788479 782335 83 Linux 0/97/35 49/20/35
+<removed>6 2097151 2097151 1 83 Linux 130/138/8 130/138/8
+-------------------
+
diff --git a/tests/ts/fdisk/mbr-logical-ebr-gap b/tests/ts/fdisk/mbr-logical-ebr-gap
new file mode 100755
index 00000000000..ffc9f96bc31
--- /dev/null
+++ b/tests/ts/fdisk/mbr-logical-ebr-gap
@@ -0,0 +1,35 @@
+#!/bin/bash
+TS_TOPDIR="${0%/*}/../.."
+TS_DESC="MBR: default start for logical must reserve EBR gap"
+. "$TS_TOPDIR"/functions.sh
+ts_init "$*"
+ts_check_test_command "$TS_CMD_FDISK"
+
+# 1GiB image => 2097152 sectors @ 512B
+TEST_IMAGE_NAME=$(ts_image_init 1024)
+
+# key assertion is in the resulting layout: L2 must not start at 788480,
+# but at 790528 (= 788480 + 2048), leaving room for the EBR.
+echo -e \
+"o
+n
+e
+1
+2048
+2097151
+n
+6145
+788479
+n
+788480
+2097151
+w
+q
+" | $TS_CMD_FDISK --noauto-pt "$TEST_IMAGE_NAME" &> /dev/null
+
+echo -ne "\n---layout----------\n" >> "$TS_OUTPUT"
+$TS_CMD_FDISK -x "$TEST_IMAGE_NAME" >> "$TS_OUTPUT"
+echo -ne "-------------------\n\n" >> "$TS_OUTPUT"
+ts_fdisk_clean "$TEST_IMAGE_NAME"
+
+ts_finalize
