From: Jonas Dreßler <verdre@v0yd.nl>
Date: Thu, 9 Jul 2026 13:22:13 +0000 (+0200)
Subject: repart: Don't copy trailing padding when using --copy-from=
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=71d20a990ecac3cac635609a4fd1772861730a54;p=thirdparty%2Fsystemd.git

repart: Don't copy trailing padding when using --copy-from=

Currently, --copy-from= copies the paddings in between the source partitions,
as well as the trailing padding that is at the end of the source partition table.
It doesn't copy the leading padding at the start of the source partition table
though.

This seems inconsistent, and likely it was an oversight that the trailing padding
is copied.

Fix that, and add a test to ensure we don't regress.
---

diff --git a/src/repart/repart.c b/src/repart/repart.c
index 838786e1532..271056a06a9 100644
--- a/src/repart/repart.c
+++ b/src/repart/repart.c
@@ -3287,10 +3287,12 @@ static int determine_current_padding(
                 struct fdisk_partition *p,
                 uint64_t secsz,
                 uint64_t grainsz,
-                uint64_t *ret) {
+                uint64_t *ret,
+                bool *ret_is_last_partition) {
 
         size_t n_partitions;
         uint64_t offset, next = UINT64_MAX;
+        bool is_last_partition = false;
 
         assert(c);
         assert(t);
@@ -3330,6 +3332,8 @@ static int determine_current_padding(
         }
 
         if (next == UINT64_MAX) {
+                is_last_partition = true;
+
                 /* No later partition? In that case check the end of the usable area */
                 next = sym_fdisk_get_last_lba(c);
                 assert(next < UINT64_MAX);
@@ -3346,6 +3350,9 @@ static int determine_current_padding(
         offset = round_up_size(offset, grainsz);
         next = round_down_size(next, grainsz);
 
+        if (ret_is_last_partition)
+                *ret_is_last_partition = is_last_partition;
+
         *ret = LESS_BY(next, offset); /* Saturated subtraction, rounding might have fucked things up */
         return 0;
 }
@@ -3395,6 +3402,7 @@ static int context_copy_from_one(Context *context, const char *src) {
                 uint64_t sz, start, padding;
                 sd_id128_t ptid, id;
                 GptPartitionType type;
+                bool is_last_partition;
 
                 p = sym_fdisk_table_get_partition(t, i);
                 if (!p)
@@ -3456,11 +3464,12 @@ static int context_copy_from_one(Context *context, const char *src) {
 
                 /* Pass grain size of 1 to disable rounding by grain as we don't know the grain size
                  * of the old image. We'll round paddings to the grain size of the new image later. */
-                r = determine_current_padding(c, t, p, secsz, /* grainsz= */ 1, &padding);
+                r = determine_current_padding(c, t, p, secsz, /* grainsz= */ 1, &padding, &is_last_partition);
                 if (r < 0)
                         return r;
 
-                np->padding_min = np->padding_max = padding;
+                if (!is_last_partition)
+                        np->padding_min = np->padding_max = padding;
 
                 np->copy_blocks_path = strdup(src);
                 if (!np->copy_blocks_path)
@@ -4056,7 +4065,14 @@ static int context_load_partition_table(Context *context) {
                                 pp->current_partition = p;
                                 sym_fdisk_ref_partition(p);
 
-                                r = determine_current_padding(c, t, p, secsz, grainsz, &pp->current_padding);
+                                r = determine_current_padding(
+                                                c,
+                                                t,
+                                                p,
+                                                secsz,
+                                                grainsz,
+                                                &pp->current_padding,
+                                                /* ret_is_last_partition= */ NULL);
                                 if (r < 0)
                                         return r;
 
@@ -4089,7 +4105,14 @@ static int context_load_partition_table(Context *context) {
                         np->current_partition = p;
                         sym_fdisk_ref_partition(p);
 
-                        r = determine_current_padding(c, t, p, secsz, grainsz, &np->current_padding);
+                        r = determine_current_padding(
+                                        c,
+                                        t,
+                                        p,
+                                        secsz,
+                                        grainsz,
+                                        &np->current_padding,
+                                        /* ret_is_last_partition= */ NULL);
                         if (r < 0)
                                 return r;
 
diff --git a/test/units/TEST-58-REPART.sh b/test/units/TEST-58-REPART.sh
index 7bd18312df9..863023454ea 100755
--- a/test/units/TEST-58-REPART.sh
+++ b/test/units/TEST-58-REPART.sh
@@ -527,6 +527,47 @@ EOF
     assert_in "$imgs/copy_to2 : start=       32768, size=       16384, type=${xbootldr_guid}," "$output"
 }
 
+testcase_copy_from_no_padding_at_beginning_and_end() {
+    local defs imgs output
+
+    defs="$(mktemp --directory "/tmp/test-repart.defs.XXXXXXXXXX")"
+    imgs="$(mktemp --directory "/var/tmp/test-repart.imgs.XXXXXXXXXX")"
+    # shellcheck disable=SC2064
+    trap "rm -rf '$defs' '$imgs'" RETURN
+    chmod 0755 "$defs"
+
+    tee "$defs/03-esp.conf" <<EOF
+[Partition]
+Type=esp
+EOF
+
+    truncate -s 80MiB "$imgs/copy_from"
+    sfdisk "$imgs/copy_from" <<EOF
+label: gpt
+
+start=2280, size=20480, type=${root_guid}, uuid=837c3d67-21b3-478e-be82-7e7f83bf96d3
+start=22760, size=10240, type=${xbootldr_guid}, uuid=4985c03e-eecb-4fe0-9f65-3f6345782214
+EOF
+
+    truncate -s 60MiB "$imgs/copy_to"
+    output=$(systemd-repart --offline="$OFFLINE" \
+                            --empty=allow \
+                            --definitions="$defs" \
+                            --seed="$seed" \
+                            --dry-run=no \
+                            --json=pretty \
+                            --copy-from="$imgs/copy_from" \
+                            "$imgs/copy_to")
+
+    output=$(sfdisk --dump "$imgs/copy_to")
+
+    assert_in "first-lba: 2048" "$output"
+    assert_in "last-lba: 122846" "$output"
+    assert_in "$imgs/copy_to1 : start=        2048, size=       20480, type=${root_guid}," "$output"
+    assert_in "$imgs/copy_to2 : start=       22528, size=       10240, type=${xbootldr_guid}," "$output"
+    assert_in "$imgs/copy_to3 : start=       32768, size=       90072, type=${esp_guid}," "$output"
+}
+
 testcase_dropin() {
     local defs imgs output