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-rw-r--r--src/basic/mount-util.c71
-rw-r--r--src/basic/mount-util.h2
-rw-r--r--src/core/namespace.c66
-rw-r--r--src/nspawn/nspawn-mount.c6
-rw-r--r--src/nspawn/nspawn.c2
5 files changed, 96 insertions, 51 deletions
diff --git a/src/basic/mount-util.c b/src/basic/mount-util.c
index bfa04394fe..b9affb4e70 100644
--- a/src/basic/mount-util.c
+++ b/src/basic/mount-util.c
@@ -36,6 +36,7 @@
#include "set.h"
#include "stdio-util.h"
#include "string-util.h"
+#include "strv.h"
static int fd_fdinfo_mnt_id(int fd, const char *filename, int flags, int *mnt_id) {
char path[strlen("/proc/self/fdinfo/") + DECIMAL_STR_MAX(int)];
@@ -287,10 +288,12 @@ int umount_recursive(const char *prefix, int flags) {
continue;
if (umount2(p, flags) < 0) {
- r = -errno;
+ r = log_debug_errno(errno, "Failed to umount %s: %m", p);
continue;
}
+ log_debug("Successfully unmounted %s", p);
+
again = true;
n++;
@@ -311,24 +314,21 @@ static int get_mount_flags(const char *path, unsigned long *flags) {
return 0;
}
-int bind_remount_recursive(const char *prefix, bool ro) {
+int bind_remount_recursive(const char *prefix, bool ro, char **blacklist) {
_cleanup_set_free_free_ Set *done = NULL;
_cleanup_free_ char *cleaned = NULL;
int r;
- /* Recursively remount a directory (and all its submounts)
- * read-only or read-write. If the directory is already
- * mounted, we reuse the mount and simply mark it
- * MS_BIND|MS_RDONLY (or remove the MS_RDONLY for read-write
- * operation). If it isn't we first make it one. Afterwards we
- * apply MS_BIND|MS_RDONLY (or remove MS_RDONLY) to all
- * submounts we can access, too. When mounts are stacked on
- * the same mount point we only care for each individual
- * "top-level" mount on each point, as we cannot
- * influence/access the underlying mounts anyway. We do not
- * have any effect on future submounts that might get
- * propagated, they migt be writable. This includes future
- * submounts that have been triggered via autofs. */
+ /* Recursively remount a directory (and all its submounts) read-only or read-write. If the directory is already
+ * mounted, we reuse the mount and simply mark it MS_BIND|MS_RDONLY (or remove the MS_RDONLY for read-write
+ * operation). If it isn't we first make it one. Afterwards we apply MS_BIND|MS_RDONLY (or remove MS_RDONLY) to
+ * all submounts we can access, too. When mounts are stacked on the same mount point we only care for each
+ * individual "top-level" mount on each point, as we cannot influence/access the underlying mounts anyway. We
+ * do not have any effect on future submounts that might get propagated, they migt be writable. This includes
+ * future submounts that have been triggered via autofs.
+ *
+ * If the "blacklist" parameter is specified it may contain a list of subtrees to exclude from the
+ * remount operation. Note that we'll ignore the blacklist for the top-level path. */
cleaned = strdup(prefix);
if (!cleaned)
@@ -385,6 +385,33 @@ int bind_remount_recursive(const char *prefix, bool ro) {
if (r < 0)
return r;
+ if (!path_startswith(p, cleaned))
+ continue;
+
+ /* Ignore this mount if it is blacklisted, but only if it isn't the top-level mount we shall
+ * operate on. */
+ if (!path_equal(cleaned, p)) {
+ bool blacklisted = false;
+ char **i;
+
+ STRV_FOREACH(i, blacklist) {
+
+ if (path_equal(*i, cleaned))
+ continue;
+
+ if (!path_startswith(*i, cleaned))
+ continue;
+
+ if (path_startswith(p, *i)) {
+ blacklisted = true;
+ log_debug("Not remounting %s, because blacklisted by %s, called for %s", p, *i, cleaned);
+ break;
+ }
+ }
+ if (blacklisted)
+ continue;
+ }
+
/* Let's ignore autofs mounts. If they aren't
* triggered yet, we want to avoid triggering
* them, as we don't make any guarantees for
@@ -396,12 +423,9 @@ int bind_remount_recursive(const char *prefix, bool ro) {
continue;
}
- if (path_startswith(p, cleaned) &&
- !set_contains(done, p)) {
-
+ if (!set_contains(done, p)) {
r = set_consume(todo, p);
p = NULL;
-
if (r == -EEXIST)
continue;
if (r < 0)
@@ -418,8 +442,7 @@ int bind_remount_recursive(const char *prefix, bool ro) {
if (!set_contains(done, cleaned) &&
!set_contains(todo, cleaned)) {
- /* The prefix directory itself is not yet a
- * mount, make it one. */
+ /* The prefix directory itself is not yet a mount, make it one. */
if (mount(cleaned, cleaned, NULL, MS_BIND|MS_REC, NULL) < 0)
return -errno;
@@ -430,6 +453,8 @@ int bind_remount_recursive(const char *prefix, bool ro) {
if (mount(NULL, prefix, NULL, orig_flags|MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0)
return -errno;
+ log_debug("Made top-level directory %s a mount point.", prefix);
+
x = strdup(cleaned);
if (!x)
return -ENOMEM;
@@ -447,8 +472,7 @@ int bind_remount_recursive(const char *prefix, bool ro) {
if (r < 0)
return r;
- /* Deal with mount points that are obstructed by a
- * later mount */
+ /* Deal with mount points that are obstructed by a later mount */
r = path_is_mount_point(x, 0);
if (r == -ENOENT || r == 0)
continue;
@@ -463,6 +487,7 @@ int bind_remount_recursive(const char *prefix, bool ro) {
if (mount(NULL, x, NULL, orig_flags|MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0)
return -errno;
+ log_debug("Remounted %s read-only.", x);
}
}
}
diff --git a/src/basic/mount-util.h b/src/basic/mount-util.h
index f46989ebb3..74730de663 100644
--- a/src/basic/mount-util.h
+++ b/src/basic/mount-util.h
@@ -35,7 +35,7 @@ int path_is_mount_point(const char *path, int flags);
int repeat_unmount(const char *path, int flags);
int umount_recursive(const char *target, int flags);
-int bind_remount_recursive(const char *prefix, bool ro);
+int bind_remount_recursive(const char *prefix, bool ro, char **blacklist);
int mount_move_root(const char *path);
diff --git a/src/core/namespace.c b/src/core/namespace.c
index 72f850b2f2..b0dab9459e 100644
--- a/src/core/namespace.c
+++ b/src/core/namespace.c
@@ -375,9 +375,19 @@ static int apply_mount(
case READONLY:
case READWRITE:
- /* Nothing to mount here, we just later toggle the
- * MS_RDONLY bit for the mount point */
- return 0;
+
+ r = path_is_mount_point(m->path, 0);
+ if (r < 0) {
+ if (m->ignore && errno == ENOENT)
+ return 0;
+ return log_debug_errno(r, "Failed to determine whether %s is already a mount point: %m", m->path);
+ }
+ if (r > 0) /* Nothing to do here, it is already a mount. We just later toggle the MS_RDONLY bit for the mount point if needed. */
+ return 0;
+
+ /* This isn't a mount point yet, let's make it one. */
+ what = m->path;
+ break;
case PRIVATE_TMP:
what = tmp_dir;
@@ -396,31 +406,33 @@ static int apply_mount(
assert(what);
- r = mount(what, m->path, NULL, MS_BIND|MS_REC, NULL);
- if (r >= 0) {
- log_debug("Successfully mounted %s to %s", what, m->path);
- return r;
- } else {
+ if (mount(what, m->path, NULL, MS_BIND|MS_REC, NULL) < 0) {
if (m->ignore && errno == ENOENT)
return 0;
+
return log_debug_errno(errno, "Failed to mount %s to %s: %m", what, m->path);
}
+
+ log_debug("Successfully mounted %s to %s", what, m->path);
+ return 0;
}
-static int make_read_only(BindMount *m) {
- int r;
+static int make_read_only(BindMount *m, char **blacklist) {
+ int r = 0;
assert(m);
if (IN_SET(m->mode, INACCESSIBLE, READONLY))
- r = bind_remount_recursive(m->path, true);
- else if (IN_SET(m->mode, READWRITE, PRIVATE_TMP, PRIVATE_VAR_TMP, PRIVATE_DEV)) {
- r = bind_remount_recursive(m->path, false);
- if (r == 0 && m->mode == PRIVATE_DEV) /* can be readonly but the submounts can't*/
- if (mount(NULL, m->path, NULL, MS_REMOUNT|DEV_MOUNT_OPTIONS|MS_RDONLY, NULL) < 0)
- r = -errno;
+ r = bind_remount_recursive(m->path, true, blacklist);
+ else if (m->mode == PRIVATE_DEV) { /* Can be readonly but the submounts can't*/
+ if (mount(NULL, m->path, NULL, MS_REMOUNT|DEV_MOUNT_OPTIONS|MS_RDONLY, NULL) < 0)
+ r = -errno;
} else
- r = 0;
+ return 0;
+
+ /* Not that we only turn on the MS_RDONLY flag here, we never turn it off. Something that was marked read-only
+ * already stays this way. This improves compatibility with container managers, where we won't attempt to undo
+ * read-only mounts already applied. */
if (m->ignore && r == -ENOENT)
return 0;
@@ -570,14 +582,25 @@ int setup_namespace(
}
if (n > 0) {
+ char **blacklist;
+ unsigned j;
+
+ /* First round, add in all special mounts we need */
for (m = mounts; m < mounts + n; ++m) {
r = apply_mount(m, tmp_dir, var_tmp_dir);
if (r < 0)
goto fail;
}
+ /* Create a blacklist we can pass to bind_mount_recursive() */
+ blacklist = newa(char*, n+1);
+ for (j = 0; j < n; j++)
+ blacklist[j] = (char*) mounts[j].path;
+ blacklist[j] = NULL;
+
+ /* Second round, flip the ro bits if necessary. */
for (m = mounts; m < mounts + n; ++m) {
- r = make_read_only(m);
+ r = make_read_only(m, blacklist);
if (r < 0)
goto fail;
}
@@ -586,9 +609,7 @@ int setup_namespace(
if (root_directory) {
/* MS_MOVE does not work on MS_SHARED so the remount MS_SHARED will be done later */
r = mount_move_root(root_directory);
-
- /* at this point, we cannot rollback */
- if (r < 0)
+ if (r < 0) /* at this point, we cannot rollback */
return r;
}
@@ -596,8 +617,7 @@ int setup_namespace(
* reestablish propagation from our side to the host, since
* what's disconnected is disconnected. */
if (mount(NULL, "/", NULL, mount_flags | MS_REC, NULL) < 0)
- /* at this point, we cannot rollback */
- return -errno;
+ return -errno; /* at this point, we cannot rollback */
return 0;
diff --git a/src/nspawn/nspawn-mount.c b/src/nspawn/nspawn-mount.c
index 295b75341f..8457357003 100644
--- a/src/nspawn/nspawn-mount.c
+++ b/src/nspawn/nspawn-mount.c
@@ -476,7 +476,7 @@ static int mount_bind(const char *dest, CustomMount *m) {
return log_error_errno(errno, "mount(%s) failed: %m", where);
if (m->read_only) {
- r = bind_remount_recursive(where, true);
+ r = bind_remount_recursive(where, true, NULL);
if (r < 0)
return log_error_errno(r, "Read-only bind mount failed: %m");
}
@@ -990,7 +990,7 @@ int setup_volatile_state(
/* --volatile=state means we simply overmount /var
with a tmpfs, and the rest read-only. */
- r = bind_remount_recursive(directory, true);
+ r = bind_remount_recursive(directory, true, NULL);
if (r < 0)
return log_error_errno(r, "Failed to remount %s read-only: %m", directory);
@@ -1065,7 +1065,7 @@ int setup_volatile(
bind_mounted = true;
- r = bind_remount_recursive(t, true);
+ r = bind_remount_recursive(t, true, NULL);
if (r < 0) {
log_error_errno(r, "Failed to remount %s read-only: %m", t);
goto fail;
diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index 0d61d34ebf..1f3e1f2dac 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -3019,7 +3019,7 @@ static int outer_child(
return r;
if (arg_read_only) {
- r = bind_remount_recursive(directory, true);
+ r = bind_remount_recursive(directory, true, NULL);
if (r < 0)
return log_error_errno(r, "Failed to make tree read-only: %m");
}
generated by cgit v1.2.3-54-g00ecf (git 2.45.2) at 2024-07-22 14:21:15 +0000