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mount: handle bind mount of file with non-existing target

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When the target (Where=) of a mount does not exist, systemd tries to
create it. But previously, it'd always been created as a directory. That
doesn't work if one wants to bind-mount a file to a target that doesn't
exist.

Fixes: #17184
(cherry picked from commit 218cfe23354397ded28ac898f82b52724f48dae7)
(cherry picked from commit 25e30725d7d31d747a40a5c0ab387dc9f48f09e3)
This commit is contained in:
David Tardon 2023-01-13 15:58:39 +01:00 committed by Luca Boccassi
parent cf62f6b727
commit 48251e428f
2 changed files with 22 additions and 4 deletions
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4
man/systemd.mount.xml
View File

@ -476,7 +476,9 @@
<term><varname>Where=</varname></term>
<listitem><para>Takes an absolute path of a file or directory for the mount point; in particular, the
destination cannot be a symbolic link. If the mount point does not exist at the time of mounting, it
is created as directory. This string must be reflected in the unit filename. (See above.) This option
is created as either a directory or a file. The former is the usual case; the latter is done only if this mount
is a bind mount and the source (<varname>What=</varname>) is not a directory.
This string must be reflected in the unit filename. (See above.) This option
is mandatory.</para></listitem>
</varlistentry>

22
src/core/mount.c
View File

@ -13,6 +13,7 @@
#include "device.h"
#include "exit-status.h"
#include "format-util.h"
#include "fs-util.h"
#include "fstab-util.h"
#include "libmount-util.h"
#include "log.h"
@ -26,11 +27,13 @@
#include "process-util.h"
#include "serialize.h"
#include "special.h"
#include "stat-util.h"
#include "string-table.h"
#include "string-util.h"
#include "strv.h"
#include "unit-name.h"
#include "unit.h"
#include "user-util.h"
#define RETRY_UMOUNT_MAX 32
@ -1043,6 +1046,7 @@ fail:
static void mount_enter_mounting(Mount *m) {
int r;
MountParameters *p;
bool source_is_dir = true;
assert(m);
@ -1050,16 +1054,28 @@ static void mount_enter_mounting(Mount *m) {
if (r < 0)
goto fail;
(void) mkdir_p_label(m->where, m->directory_mode);
p = get_mount_parameters_fragment(m);
if (p && mount_is_bind(p)) {
r = is_dir(p->what, /* follow = */ true);
if (r < 0 && r != -ENOENT)
log_unit_info_errno(UNIT(m), r, "Failed to determine type of bind mount source '%s', ignoring: %m", p->what);
else if (r == 0)
source_is_dir = false;
}
unit_warn_if_dir_nonempty(UNIT(m), m->where);
if (source_is_dir)
(void) mkdir_p_label(m->where, m->directory_mode);
else
(void) touch_file(m->where, /* parents = */ true, USEC_INFINITY, UID_INVALID, GID_INVALID, MODE_INVALID);
if (source_is_dir)
unit_warn_if_dir_nonempty(UNIT(m), m->where);
unit_warn_leftover_processes(UNIT(m), unit_log_leftover_process_start);
m->control_command_id = MOUNT_EXEC_MOUNT;
m->control_command = m->exec_command + MOUNT_EXEC_MOUNT;
/* Create the source directory for bind-mounts if needed */
p = get_mount_parameters_fragment(m);
if (p && mount_is_bind(p)) {
r = mkdir_p_label(p->what, m->directory_mode);
/* mkdir_p_label() can return -EEXIST if the target path exists and is not a directory - which is