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shared/install: when creating symlinks, accept different but equivalent symlinks

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We would only accept "identical" links, but having e.g. a symlink
/usr/lib/systemd/system/foo-alias.service → /usr/lib/systemd/system/foo.service
when we're trying to create /usr/lib/systemd/system/foo-alias.service →
./foo.service is OK. This fixes an issue found in ubuntuautopkg package
installation, where we'd fail when enabling systemd-resolved.service, because
the existing alias was absolute, and (with the recent patches) we were trying
to create a relative one.

A test is added.
(For .wants/.requires symlinks we were already doing OK. A test is also
added, to verify.)
This commit is contained in:
Zbigniew Jędrzejewski-Szmek
2022-03-25 15:43:27 +01:00
parent 84fdced62c
commit 3fc53351dc
2 changed files with 81 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

59
src/shared/install.c
View File

@@ -423,21 +423,54 @@ void unit_file_dump_changes(int r, const char *verb, const UnitFileChange *chang
}
/**
* Checks if two paths or symlinks from wd are the same, when root is the root of the filesystem.
* wc should be the full path in the host file system.
* Checks if two symlink targets (starting from src) are equivalent as far as the unit enablement logic is
* concerned. If the target is in the unit search path, then anything with the same name is equivalent.
* If outside the unit search path, paths must be identical.
*/
static bool chroot_symlinks_same(const char *root, const char *wd, const char *a, const char *b) {
assert(path_is_absolute(wd));
static int chroot_unit_symlinks_equivalent(
const LookupPaths *lp,
const char *src,
const char *target_a,
const char *target_b) {
assert(lp);
assert(src);
assert(target_a);
assert(target_b);
/* This will give incorrect results if the paths are relative and go outside
* of the chroot. False negatives are possible. */
if (!root)
root = "/";
const char *root = lp->root_dir ?: "/";
_cleanup_free_ char *dirname = NULL;
int r;
a = strjoina(path_is_absolute(a) ? root : wd, "/", a);
b = strjoina(path_is_absolute(b) ? root : wd, "/", b);
return path_equal_or_files_same(a, b, 0);
if (!path_is_absolute(target_a) || !path_is_absolute(target_b)) {
r = path_extract_directory(src, &dirname);
if (r < 0)
return r;
}
_cleanup_free_ char *a = path_join(path_is_absolute(target_a) ? root : dirname, target_a);
_cleanup_free_ char *b = path_join(path_is_absolute(target_b) ? root : dirname, target_b);
if (!a || !b)
return log_oom();
r = path_equal_or_files_same(a, b, 0);
if (r != 0)
return r;
_cleanup_free_ char *a_name = NULL, *b_name = NULL;
r = path_extract_filename(a, &a_name);
if (r < 0)
return r;
r = path_extract_filename(b, &b_name);
if (r < 0)
return r;
return streq(a_name, b_name) &&
path_startswith_strv(a, lp->search_path) &&
path_startswith_strv(b, lp->search_path);
}
static int create_symlink(
@@ -448,7 +481,7 @@ static int create_symlink(
UnitFileChange **changes,
size_t *n_changes) {
_cleanup_free_ char *dest = NULL, *dirname = NULL;
_cleanup_free_ char *dest = NULL;
const char *rp;
int r;
@@ -488,11 +521,7 @@ static int create_symlink(
return r;
}
dirname = dirname_malloc(new_path);
if (!dirname)
return -ENOMEM;
if (chroot_symlinks_same(lp->root_dir, dirname, dest, old_path)) {
if (chroot_unit_symlinks_equivalent(lp, new_path, dest, old_path)) {
log_debug("Symlink %s → %s already exists", new_path, dest);
return 1;
}

39
test/test-systemctl-enable.sh
View File

@@ -39,8 +39,29 @@ test -h "$root/etc/systemd/system/default.target.wants/test1.service"
test -h "$root/etc/systemd/system/special.target.requires/test1.service"
"$systemctl" --root="$root" disable test1.service
test ! -e "$root/etc/systemd/system/default.target.wants/test1.service"
test ! -e "$root/etc/systemd/system/special.target.requires/test1.service"
test ! -h "$root/etc/systemd/system/default.target.wants/test1.service"
test ! -h "$root/etc/systemd/system/special.target.requires/test1.service"
: '------enable when link already exists-----------------------'
# We don't read the symlink target, so it's OK for the symlink to point
# to something else. We should just silently accept this.
mkdir -p "$root/etc/systemd/system/default.target.wants"
mkdir -p "$root/etc/systemd/system/special.target.requires"
ln -s /usr/lib/systemd/system/test1.service "$root/etc/systemd/system/default.target.wants/test1.service"
ln -s /usr/lib/systemd/system/test1.service "$root/etc/systemd/system/special.target.requires/test1.service"
"$systemctl" --root="$root" enable test1.service
test -h "$root/etc/systemd/system/default.target.wants/test1.service"
test -h "$root/etc/systemd/system/special.target.requires/test1.service"
"$systemctl" --root="$root" reenable test1.service
test -h "$root/etc/systemd/system/default.target.wants/test1.service"
test -h "$root/etc/systemd/system/special.target.requires/test1.service"
"$systemctl" --root="$root" disable test1.service
test ! -h "$root/etc/systemd/system/default.target.wants/test1.service"
test ! -h "$root/etc/systemd/system/special.target.requires/test1.service"
: '------suffix guessing---------------------------------------'
"$systemctl" --root="$root" enable test1
@@ -90,6 +111,20 @@ test ! -h "$root/etc/systemd/system/default.target.wants/test1.service"
test ! -h "$root/etc/systemd/system/special.target.requires/test1.service"
test ! -h "$root/etc/systemd/system/test1-goodalias.service"
: '-------aliases when link already exists---------------------'
cat >"$root/etc/systemd/system/test1a.service" <<EOF
[Install]
Alias=test1a-alias.service
EOF
ln -s /usr/lib/systemd/system/test1a.service "$root/etc/systemd/system/test1a-alias.service"
"$systemctl" --root="$root" enable test1a.service
test -h "$root/etc/systemd/system/test1a-alias.service"
"$systemctl" --root="$root" disable test1a.service
test ! -h "$root/etc/systemd/system/test1a-alias.service"
: '-------also units-------------------------------------------'
cat >"$root/etc/systemd/system/test2.socket" <<EOF
[Install]