core: port mount unit inode creation to make_mount_point_inode_from_mode() too

This also ports over things to use chase() to create/pin the underlying
to mount, and in particular checks that the path does not contain any
symlinks. That's crucial since we cannot allow mounts to be established
with that, since it would mean we couldn't recognize the entries in
/proc/self/mountinfo anymore.

diff --git a/src/core/automount.c b/src/core/automount.c
index ac81875442eb6aed78aa179f5fb5e60159240991..5ac5dec8d9da95f2bb212a2169b3ae675ee56db8 100644 (file)
--- a/src/core/automount.c
+++ b/src/core/automount.c
@@ -556,7 +556,7 @@ static void automount_enter_waiting(Automount *a) {
 
         set_clear(a->tokens);
 
-        r = unit_fail_if_noncanonical(UNIT(a), a->where);
+        r = unit_fail_if_noncanonical_mount_path(UNIT(a), a->where);
         if (r < 0)
                 goto fail;
 

diff --git a/src/core/mount.c b/src/core/mount.c
index d7557bf3897531bc7ee78a6ce8e57f08245308a4..361d8e031896a23e8f8cc029182a977f2e7df8ff 100644 (file)
--- a/src/core/mount.c
+++ b/src/core/mount.c
@@ -8,11 +8,13 @@
 #include "sd-messages.h"
 
 #include "alloc-util.h"
+#include "chase.h"
 #include "dbus-mount.h"
 #include "dbus-unit.h"
 #include "device.h"
 #include "exec-credential.h"
 #include "exit-status.h"
+#include "fd-util.h"
 #include "format-util.h"
 #include "fs-util.h"
 #include "fstab-util.h"
@@ -1183,22 +1185,32 @@ static int mount_set_mount_command(Mount *m, ExecCommand *c, const MountParamete
 }
 
 static void mount_enter_mounting(Mount *m) {
-        MountParameters *p;
-        bool source_is_dir = true;
+        _cleanup_close_ int fd = -EBADF;
+        _cleanup_free_ char *fn = NULL;
         int r;
 
         assert(m);
 
-        r = unit_fail_if_noncanonical(UNIT(m), m->where);
-        if (r < 0)
+        /* Validate that the path we are overmounting does not contain any symlinks, because if it does, we
+         * couldn't support that reasonably: the mounts in /proc/self/mountinfo would not be recognizable to
+         * us anymore. */
+        fd = chase_and_open_parent(m->where, /* root= */ NULL, CHASE_PROHIBIT_SYMLINKS|CHASE_MKDIR_0755, &fn);
+        if (fd == -EREMCHG) {
+                r = unit_log_noncanonical_mount_path(UNIT(m), m->where);
+                goto fail;
+        }
+        if (fd < 0) {
+                log_unit_error_errno(UNIT(m), fd, "Failed to resolve parent of mount point '%s': %m", m->where);
                 goto fail;
+        }
 
-        p = get_mount_parameters_fragment(m);
+        MountParameters *p = get_mount_parameters_fragment(m);
         if (!p) {
                 r = log_unit_warning_errno(UNIT(m), SYNTHETIC_ERRNO(ENOENT), "No mount parameters to operate on.");
                 goto fail;
         }
 
+        bool source_is_dir = true;
         if (mount_is_bind(p)) {
                 r = is_dir(p->what, /* follow = */ true);
                 if (r < 0 && r != -ENOENT)
@@ -1207,10 +1219,11 @@ static void mount_enter_mounting(Mount *m) {
                         source_is_dir = false;
         }
 
-        if (source_is_dir)
-                r = mkdir_p_label(m->where, m->directory_mode);
-        else
-                r = touch_file(m->where, /* parents = */ true, USEC_INFINITY, UID_INVALID, GID_INVALID, MODE_INVALID);
+        r = make_mount_point_inode_from_mode(
+                        fd,
+                        fn,
+                        source_is_dir ? S_IFDIR : S_IFREG,
+                        m->directory_mode);
         if (r < 0 && r != -EEXIST)
                 log_unit_warning_errno(UNIT(m), r, "Failed to create mount point '%s', ignoring: %m", m->where);
 

diff --git a/src/core/unit.c b/src/core/unit.c
index 3f4432f6556af2f3ce97275bdb8168f0b855f931..9160876635128e52f3e3a6a8ce0d2dc460e4d33e 100644 (file)
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -5125,14 +5125,28 @@ void unit_warn_if_dir_nonempty(Unit *u, const char* where) {
                         "WHERE=%s", where);
 }
 
-int unit_fail_if_noncanonical(Unit *u, const char* where) {
-        _cleanup_free_ char *canonical_where = NULL;
+int unit_log_noncanonical_mount_path(Unit *u, const char *where) {
+        assert(u);
+        assert(where);
+
+        /* No need to mention "." or "..", they would already have been rejected by unit_name_from_path() */
+        log_unit_struct(u, LOG_ERR,
+                        "MESSAGE_ID=" SD_MESSAGE_OVERMOUNTING_STR,
+                        LOG_UNIT_INVOCATION_ID(u),
+                        LOG_UNIT_MESSAGE(u, "Mount path %s is not canonical (contains a symlink).", where),
+                        "WHERE=%s", where);
+
+        return -ELOOP;
+}
+
+int unit_fail_if_noncanonical_mount_path(Unit *u, const char* where) {
         int r;
 
         assert(u);
         assert(where);
 
-        r = chase(where, NULL, CHASE_NONEXISTENT, &canonical_where, NULL);
+        _cleanup_free_ char *canonical_where = NULL;
+        r = chase(where, /* root= */ NULL, CHASE_NONEXISTENT, &canonical_where, /* ret_fd= */ NULL);
         if (r < 0) {
                 log_unit_debug_errno(u, r, "Failed to check %s for symlinks, ignoring: %m", where);
                 return 0;
@@ -5142,14 +5156,7 @@ int unit_fail_if_noncanonical(Unit *u, const char* where) {
         if (path_equal(where, canonical_where))
                 return 0;
 
-        /* No need to mention "." or "..", they would already have been rejected by unit_name_from_path() */
-        log_unit_struct(u, LOG_ERR,
-                        "MESSAGE_ID=" SD_MESSAGE_OVERMOUNTING_STR,
-                        LOG_UNIT_INVOCATION_ID(u),
-                        LOG_UNIT_MESSAGE(u, "Mount path %s is not canonical (contains a symlink).", where),
-                        "WHERE=%s", where);
-
-        return -ELOOP;
+        return unit_log_noncanonical_mount_path(u, where);
 }
 
 bool unit_is_pristine(Unit *u) {

diff --git a/src/core/unit.h b/src/core/unit.h
index 45b7d72b7afd7cb7ebda98e842c471ffd83e6c02..4b19d8f0f751744bdbf15fff95edd7e38aae333a 100644 (file)
--- a/src/core/unit.h
+++ b/src/core/unit.h
@@ -974,7 +974,8 @@ static inline PidRef* unit_main_pid(Unit *u) {
 }
 
 void unit_warn_if_dir_nonempty(Unit *u, const char* where);
-int unit_fail_if_noncanonical(Unit *u, const char* where);
+int unit_log_noncanonical_mount_path(Unit *u, const char *where);
+int unit_fail_if_noncanonical_mount_path(Unit *u, const char* where);
 
 int unit_test_start_limit(Unit *u);