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namespace: beef up read-only bind mount logic

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Instead of blindly creating another bind mount for read-only mounts,
check if there's already one we can use, and if so, use it. Also,
recursively mark all submounts read-only too. Also, ignore autofs mounts
when remounting read-only unless they are already triggered.
This commit is contained in:
Lennart Poettering
2014-06-06 14:37:40 +02:00
parent c8835999c3
commit d6797c920e
5 changed files with 183 additions and 31 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/core/namespace.c
+16 -12
View File
@@ -280,9 +280,6 @@ static int apply_mount(
switch (m->mode) {
case PRIVATE_DEV:
return mount_dev(m);
case INACCESSIBLE:
/* First, get rid of everything that is below if there
@@ -295,8 +292,9 @@ static int apply_mount(
case READONLY:
case READWRITE:
what = m->path;
break;
/* Nothing to mount here, we just later toggle the
* MS_RDONLY bit for the mount point */
return 0;
case PRIVATE_TMP:
what = tmp_dir;
@@ -306,6 +304,9 @@ static int apply_mount(
what = var_tmp_dir;
break;
case PRIVATE_DEV:
return mount_dev(m);
default:
assert_not_reached("Unknown mode");
}
@@ -316,7 +317,7 @@ static int apply_mount(
if (r >= 0)
log_debug("Successfully mounted %s to %s", what, m->path);
else if (m->ignore && errno == ENOENT)
r = 0;
return 0;
return r;
}
@@ -326,14 +327,17 @@ static int make_read_only(BindMount *m) {
assert(m);
if (m->mode != INACCESSIBLE && m->mode != READONLY)
if (IN_SET(m->mode, INACCESSIBLE, READONLY))
r = bind_remount_recursive(m->path, true);
else if (m->mode == READWRITE)
r = bind_remount_recursive(m->path, false);
else
r = 0;
if (m->ignore && r == -ENOENT)
return 0;
r = mount(NULL, m->path, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY|MS_REC, NULL);
if (r < 0 && !(m->ignore && errno == ENOENT))
return -errno;
return 0;
return r;
}
int setup_namespace(
src/nspawn/nspawn.c
+15 -10
View File
@@ -635,7 +635,7 @@ static int mount_all(const char *dest) {
return r;
}
static int mount_binds(const char *dest, char **l, unsigned long flags) {
static int mount_binds(const char *dest, char **l, bool ro) {
char **x, **y;
STRV_FOREACH_PAIR(x, y, l) {
@@ -686,9 +686,12 @@ static int mount_binds(const char *dest, char **l, unsigned long flags) {
return -errno;
}
if (flags && mount(NULL, where, NULL, MS_REMOUNT|MS_BIND|flags, NULL) < 0) {
log_error("mount(%s) failed: %m", where);
return -errno;
if (ro) {
r = bind_remount_recursive(where, true);
if (r < 0) {
log_error("Read-Only bind mount failed: %s", strerror(-r));
return r;
}
}
}
@@ -2941,15 +2944,17 @@ int main(int argc, char *argv[]) {
/* Turn directory into bind mount */
if (mount(arg_directory, arg_directory, "bind", MS_BIND|MS_REC, NULL) < 0) {
log_error("Failed to make bind mount.");
log_error("Failed to make bind mount: %m");
goto child_fail;
}
if (arg_read_only)
if (mount(arg_directory, arg_directory, "bind", MS_BIND|MS_REMOUNT|MS_RDONLY|MS_REC, NULL) < 0) {
log_error("Failed to make read-only.");
if (arg_read_only) {
k = bind_remount_recursive(arg_directory, true);
if (k < 0) {
log_error("Failed to make tree read-only: %s", strerror(-k));
goto child_fail;
}
}
if (mount_all(arg_directory) < 0)
goto child_fail;
@@ -2985,10 +2990,10 @@ int main(int argc, char *argv[]) {
if (setup_journal(arg_directory) < 0)
goto child_fail;
if (mount_binds(arg_directory, arg_bind, 0) < 0)
if (mount_binds(arg_directory, arg_bind, false) < 0)
goto child_fail;
if (mount_binds(arg_directory, arg_bind_ro, MS_RDONLY) < 0)
if (mount_binds(arg_directory, arg_bind_ro, true) < 0)
goto child_fail;
if (setup_kdbus(arg_directory, kdbus_domain) < 0)
src/shared/util.c
+144 -1
View File
@@ -6540,7 +6540,6 @@ int umount_recursive(const char *prefix, int flags) {
"%*s" /* (11) mount options 2 */
"%*[^\n]", /* some rubbish at the end */
&path);
if (k != 1) {
if (k == EOF)
break;
@@ -6570,3 +6569,147 @@ int umount_recursive(const char *prefix, int flags) {
return r ? r : n;
}
int bind_remount_recursive(const char *prefix, bool ro) {
_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. */
cleaned = strdup(prefix);
if (!cleaned)
return -ENOMEM;
path_kill_slashes(cleaned);
done = set_new(string_hash_func, string_compare_func);
if (!done)
return -ENOMEM;
for (;;) {
_cleanup_fclose_ FILE *proc_self_mountinfo = NULL;
_cleanup_set_free_free_ Set *todo = NULL;
bool top_autofs = false;
char *x;
todo = set_new(string_hash_func, string_compare_func);
if (!todo)
return -ENOMEM;
proc_self_mountinfo = fopen("/proc/self/mountinfo", "re");
if (!proc_self_mountinfo)
return -errno;
for (;;) {
_cleanup_free_ char *path = NULL, *p = NULL, *type = NULL;
int k;
k = fscanf(proc_self_mountinfo,
"%*s " /* (1) mount id */
"%*s " /* (2) parent id */
"%*s " /* (3) major:minor */
"%*s " /* (4) root */
"%ms " /* (5) mount point */
"%*s" /* (6) mount options (superblock) */
"%*[^-]" /* (7) optional fields */
"- " /* (8) separator */
"%ms " /* (9) file system type */
"%*s" /* (10) mount source */
"%*s" /* (11) mount options (bind mount) */
"%*[^\n]", /* some rubbish at the end */
&path,
&type);
if (k != 2) {
if (k == EOF)
break;
continue;
}
p = cunescape(path);
if (!p)
return -ENOMEM;
/* 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
* future submounts anyway. If they are
* already triggered, then we will find
* another entry for this. */
if (streq(type, "autofs")) {
top_autofs = top_autofs || path_equal(cleaned, p);
continue;
}
if (path_startswith(p, cleaned) &&
!set_contains(done, p)) {
r = set_consume(todo, p);
p = NULL;
if (r == -EEXIST)
continue;
if (r < 0)
return r;
}
}
/* If we have no submounts to process anymore and if
* the root is either already done, or an autofs, we
* are done */
if (set_isempty(todo) &&
(top_autofs || set_contains(done, cleaned)))
return 0;
if (!set_contains(done, cleaned) &&
!set_contains(todo, cleaned)) {
/* 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;
if (mount(NULL, prefix, NULL, MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0)
return -errno;
x = strdup(cleaned);
if (!x)
return -ENOMEM;
r = set_consume(done, x);
if (r < 0)
return r;
}
while ((x = set_steal_first(todo))) {
r = set_consume(done, x);
if (r == -EEXIST)
continue;
if (r < 0)
return r;
if (mount(NULL, x, NULL, MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0) {
/* Deal with mount points that are
* obstructed by a later mount */
if (errno != ENOENT)
return -errno;
}
}
}
}
src/shared/util.h
+2
View File
@@ -944,3 +944,5 @@ union file_handle_union {
int update_reboot_param_file(const char *param);
int umount_recursive(const char *target, int flags);
int bind_remount_recursive(const char *prefix, bool ro);