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core/exec-invoke: switch PRIVATE_USERS_FULL to direct "0 0 UINT32_MAX" mapping

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This was intended for v259. Let's get it done now, in v260.
This commit is contained in:
Mike Yuan
2026-01-23 19:29:48 +01:00
parent 6ed05d6414
commit 24c73c7920
2 changed files with 7 additions and 19 deletions
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src/core/exec-invoke.c
+5 -17
View File
@@ -2421,28 +2421,16 @@ static int setup_private_users(PrivateUsers private_users, uid_t ouid, gid_t ogi
if (!uid_map)
return -ENOMEM;
} else if (private_users == PRIVATE_USERS_FULL) {
/* Map all UID/GID from original to new user namespace. We can't use `0 0 UINT32_MAX` because
* this is the same UID/GID map as the init user namespace and systemd's running_in_userns()
* checks whether its in a user namespace by comparing uid_map/gid_map to `0 0 UINT32_MAX`.
* Thus, we still map all UIDs/GIDs but do it using two extents to differentiate the new user
* namespace from the init namespace:
* 0 0 1
* 1 1 UINT32_MAX - 1
*
* systemd will remove the heuristic in running_in_userns() and use namespace inodes in version 258
* (PR #35382). But some users may be running a container image with older systemd < 258 so we keep
* this uid_map/gid_map hack until version 259 for version N-1 compatibility.
*
* TODO: Switch to `0 0 UINT32_MAX` in systemd v259.
/* Map all UID/GID from original to new user namespace.
*
* Note the kernel defines the UID range between 0 and UINT32_MAX so we map all UIDs even though
* the UID range beyond INT32_MAX (e.g. i.e. the range above the signed 32-bit range) is
* icky. For example, setfsuid() returns the old UID as signed integer. But units can decide to
* use these UIDs/GIDs so we need to map them. */
r = asprintf(&uid_map, "0 0 1\n"
"1 1 " UID_FMT "\n", (uid_t) (UINT32_MAX - 1));
r = asprintf(&uid_map, "0 0 " UID_FMT "\n", (uid_t) UINT32_MAX);
if (r < 0)
return -ENOMEM;
/* Can only set up multiple mappings with CAP_SETUID. */
} else if (have_effective_cap(CAP_SETUID) > 0 && uid != ouid && uid_is_valid(uid)) {
r = asprintf(&uid_map,
@@ -2464,10 +2452,10 @@ static int setup_private_users(PrivateUsers private_users, uid_t ouid, gid_t ogi
if (!gid_map)
return -ENOMEM;
} else if (private_users == PRIVATE_USERS_FULL) {
r = asprintf(&gid_map, "0 0 1\n"
"1 1 " GID_FMT "\n", (gid_t) (UINT32_MAX - 1));
r = asprintf(&gid_map, "0 0 " GID_FMT "\n", (gid_t) UINT32_MAX);
if (r < 0)
return -ENOMEM;
/* Can only set up multiple mappings with CAP_SETGID. */
} else if (have_effective_cap(CAP_SETGID) > 0 && gid != ogid && gid_is_valid(gid)) {
r = asprintf(&gid_map,
test/units/TEST-07-PID1.private-users.sh
+2 -2
View File
@@ -12,6 +12,6 @@ systemd-run -p PrivateUsersEx=self --wait bash -c 'test "$(cat /proc/self/gid_ma
systemd-run -p PrivateUsersEx=self --wait bash -c 'test "$(cat /proc/self/setgroups)" == "deny"'
systemd-run -p PrivateUsersEx=identity --wait bash -c 'test "$(cat /proc/self/uid_map)" == " 0 0 65536"'
systemd-run -p PrivateUsersEx=identity --wait bash -c 'test "$(cat /proc/self/gid_map)" == " 0 0 65536"'
systemd-run -p PrivateUsersEx=full --wait bash -c 'test "$(cat /proc/self/uid_map | tr -d "\n")" == " 0 0 1 1 1 4294967294"'
systemd-run -p PrivateUsersEx=full --wait bash -c 'test "$(cat /proc/self/gid_map | tr -d "\n")" == " 0 0 1 1 1 4294967294"'
systemd-run -p PrivateUsersEx=full --wait bash -c 'test "$(cat /proc/self/uid_map)" == " 0 0 4294967295"'
systemd-run -p PrivateUsersEx=full --wait bash -c 'test "$(cat /proc/self/gid_map)" == " 0 0 4294967295"'
systemd-run -p PrivateUsersEx=full --wait bash -c 'test "$(cat /proc/self/setgroups)" == "allow"'