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core/dynamic-user: drop unused /run/systemd/dynamic-uid/direct: kludge

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Follow-up for 1684c56f40
This effectively reverts fd63e712b2

This was originally introduced to resolve deadlock caused by
dbus broker calling into nss-systemd which in turn goes via
dbus for user lookup. This is now handled differently and
the interface has been sitting unused for half a decade now.
Kill it.
This commit is contained in:
Mike Yuan
2026-01-02 04:28:01 +09:00
committed by Yu Watanabe
parent aec52c1e6e
commit 05aea9f73b
1 changed files with 5 additions and 46 deletions
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src/core/dynamic-user.c
+5 -46
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@@ -145,44 +145,6 @@ static int dynamic_user_acquire(Manager *m, const char *name, DynamicUser** ret)
return 1;
}
static int make_uid_symlinks(uid_t uid, const char *name, bool b) {
char path1[STRLEN("/run/systemd/dynamic-uid/direct:") + DECIMAL_STR_MAX(uid_t) + 1];
const char *path2;
int r = 0, k;
/* Add direct additional symlinks for direct lookups of dynamic UIDs and their names by userspace code. The
* only reason we have this is because dbus-daemon cannot use D-Bus for resolving users and groups (since it
* would be its own client then). We hence keep these world-readable symlinks in place, so that the
* unprivileged dbus user can read the mappings when it needs them via these symlinks instead of having to go
* via the bus. Ideally, we'd use the lock files we keep for this anyway, but we can't since we use BSD locks
* on them and as those may be taken by any user with read access we can't make them world-readable. */
xsprintf(path1, "/run/systemd/dynamic-uid/direct:" UID_FMT, uid);
if (unlink(path1) < 0 && errno != ENOENT)
r = -errno;
if (b && symlink(name, path1) < 0) {
k = log_warning_errno(errno, "Failed to symlink \"%s\": %m", path1);
if (r == 0)
r = k;
}
path2 = strjoina("/run/systemd/dynamic-uid/direct:", name);
if (unlink(path2) < 0 && errno != ENOENT) {
k = -errno;
if (r == 0)
r = k;
}
if (b && symlink(path1 + STRLEN("/run/systemd/dynamic-uid/direct:"), path2) < 0) {
k = log_warning_errno(errno, "Failed to symlink \"%s\": %m", path2);
if (r == 0)
r = k;
}
return r;
}
static int pick_uid(char **suggested_paths, const char *name, uid_t *ret_uid) {
/* Find a suitable free UID. We use the following strategy to find a suitable UID:
@@ -315,7 +277,6 @@ static int pick_uid(char **suggested_paths, const char *name, uid_t *ret_uid) {
}
(void) ftruncate(lock_fd, l);
(void) make_uid_symlinks(candidate, name, true); /* also add direct lookup symlinks */
*ret_uid = candidate;
return TAKE_FD(lock_fd);
@@ -359,7 +320,7 @@ static int dynamic_user_push(DynamicUser *d, uid_t uid, int lock_fd) {
return send_one_fd_iov(d->storage_socket[1], lock_fd, &iov, 1, MSG_DONTWAIT);
}
static void unlink_uid_lock(int lock_fd, uid_t uid, const char *name) {
static void unlink_uid_lock(int lock_fd, uid_t uid) {
char lock_path[STRLEN("/run/systemd/dynamic-uid/") + DECIMAL_STR_MAX(uid_t) + 1];
if (lock_fd < 0)
@@ -367,8 +328,6 @@ static void unlink_uid_lock(int lock_fd, uid_t uid, const char *name) {
xsprintf(lock_path, "/run/systemd/dynamic-uid/" UID_FMT, uid);
(void) unlink(lock_path);
(void) make_uid_symlinks(uid, name, false); /* remove direct lookup symlinks */
}
static int dynamic_user_realize(
@@ -456,7 +415,7 @@ static int dynamic_user_realize(
/* So, we found a working UID/lock combination. Let's see if we actually still need it. */
r = posix_lock(d->storage_socket[0], LOCK_EX);
if (r < 0) {
unlink_uid_lock(uid_lock_fd, num, d->name);
unlink_uid_lock(uid_lock_fd, num);
return r;
}
@@ -464,14 +423,14 @@ static int dynamic_user_realize(
if (r < 0) {
if (r != -EAGAIN) {
/* OK, something bad happened, let's get rid of the bits we acquired. */
unlink_uid_lock(uid_lock_fd, num, d->name);
unlink_uid_lock(uid_lock_fd, num);
return r;
}
} else {
/* Hmm, so as it appears there's now something stored in the storage socket.
* Throw away what we acquired, and use what's stored now. */
unlink_uid_lock(uid_lock_fd, num, d->name);
unlink_uid_lock(uid_lock_fd, num);
safe_close(uid_lock_fd);
num = new_uid;
@@ -570,7 +529,7 @@ static int dynamic_user_close(DynamicUser *d) {
return r;
/* This dynamic user was realized and dynamically allocated. In this case, let's remove the lock file. */
unlink_uid_lock(lock_fd, uid, d->name);
unlink_uid_lock(lock_fd, uid);
return 1;
}