SymbX/systemd
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

namespace: instead of chasing mount symlinks a priori, do so as-we-go

Browse Source 
This is relevant as many of the mounts we try to establish only can be followed
when some other prior mount that is a prefix of it is established. Hence: move
the symlink chasing into the actual mount functions, so that we do it as late
as possibly but as early as necessary.

Fixes: #4588
This commit is contained in:
Lennart Poettering
2016-12-14 00:51:37 +01:00
parent 34de407a4f
commit 8fceda937f
1 changed files with 34 additions and 52 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/core/namespace.c
+34 -52
View File
@@ -568,7 +568,33 @@ fail:
return r;
}
static int mount_entry_chase(MountEntry *m, const char *root_directory) {
char *chased;
int r;
assert(m);
/* Since mount() will always follow symlinks and we need to take the different root directory into account we
* chase the symlinks on our own first. */
r = chase_symlinks(mount_entry_path(m), root_directory, 0, &chased);
if (r == -ENOENT && m->ignore) {
log_debug_errno(r, "Path %s does not exist, ignoring.", mount_entry_path(m));
return 0;
}
if (r < 0)
return log_debug_errno(r, "Failed to follow symlinks on %s: %m", mount_entry_path(m));
log_debug("Followed symlinks %s → %s.", mount_entry_path(m), chased);
free(m->path_malloc);
m->path_malloc = chased;
return 1;
}
static int apply_mount(
const char *root_directory,
MountEntry *m,
const char *tmp_dir,
const char *var_tmp_dir) {
@@ -578,6 +604,10 @@ static int apply_mount(
assert(m);
r = mount_entry_chase(m, root_directory);
if (r <= 0)
return r;
log_debug("Applying namespace mount on %s", mount_entry_path(m));
switch (m->mode) {
@@ -604,7 +634,7 @@ static int apply_mount(
case READONLY:
case READWRITE:
r = path_is_mount_point(mount_entry_path(m), NULL, 0);
r = path_is_mount_point(mount_entry_path(m), root_directory, 0);
if (r < 0)
return log_debug_errno(r, "Failed to determine whether %s is already a mount point: %m", mount_entry_path(m));
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. */
@@ -654,50 +684,9 @@ static int make_read_only(MountEntry *m, char **blacklist) {
* already stays this way. This improves compatibility with container managers, where we won't attempt to undo
* read-only mounts already applied. */
return r;
}
if (r == -ENOENT && m->ignore)
r = 0;
/* Chase symlinks and remove failed paths from mounts */
static int chase_all_symlinks(const char *root_directory, MountEntry *m, unsigned *n) {
MountEntry *f, *t;
int r = 0;
assert(m);
assert(n);
/* Since mount() will always follow symlinks and we need to take the different root directory into account we
* chase the symlinks on our own first. This call wil do so for all entries and remove all entries where we
* can't resolve the path, and which have been marked for such removal. */
for (f = m, t = m; f < m + *n; f++) {
_cleanup_free_ char *chased = NULL;
int k;
k = chase_symlinks(mount_entry_path(f), root_directory, 0, &chased);
if (k < 0) {
/* Get only real errors */
if (r >= 0 && (k != -ENOENT || !f->ignore))
r = k;
/* Doesn't exist or failed? Then remove it and continue! */
log_debug_errno(k, "Failed to chase symlinks for %s: %m", mount_entry_path(f));
f->path_malloc = mfree(f->path_malloc);
continue;
}
if (!path_equal(mount_entry_path(f), chased)) {
log_debug("Chased %s → %s", mount_entry_path(f), chased);
free(f->path_malloc);
f->path_malloc = chased;
chased = NULL;
}
*t = *f;
t++;
}
*n = t - m;
return r;
}
@@ -838,13 +827,6 @@ int setup_namespace(
if (r < 0)
goto finish;
/* Resolve symlinks manually first, as mount() will always follow them relative to the host's
* root. Moreover we want to suppress duplicates based on the resolved paths. This of course is a bit
* racy. */
r = chase_all_symlinks(root_directory, mounts, &n_mounts);
if (r < 0)
goto finish;
qsort(mounts, n_mounts, sizeof(MountEntry), mount_path_compare);
drop_duplicates(mounts, &n_mounts);
@@ -886,7 +868,7 @@ int setup_namespace(
/* First round, add in all special mounts we need */
for (m = mounts; m < mounts + n_mounts; ++m) {
r = apply_mount(m, tmp_dir, var_tmp_dir);
r = apply_mount(root_directory, m, tmp_dir, var_tmp_dir);
if (r < 0)
goto finish;
}