Lennart Poettering
319a4f4bc4
We recently started making more use of malloc_usable_size() and rely on it (see the string_erase() story). Given that we don't really support sytems where malloc_usable_size() cannot be trusted beyond statistics anyway, let's go fully in and rework GREEDY_REALLOC() on top of it: instead of passing around and maintaining the currenly allocated size everywhere, let's just derive it automatically from malloc_usable_size(). I am mostly after this for the simplicity this brings. It also brings minor efficiency improvements I guess, but things become so much nicer to look at if we can avoid these allocation size variables everywhere. Note that the malloc_usable_size() man page says relying on it wasn't "good programming practice", but I think it does this for reasons that don't apply here: the greedy realloc logic specifically doesn't rely on the returned extra size, beyond the fact that it is equal or larger than what was requested. (This commit was supposed to be a quick patch btw, but apparently we use the greedy realloc stuff quite a bit across the codebase, so this ends up touching *a*lot* of code.)
246 lines
7.3 KiB
C
246 lines
7.3 KiB
C
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#include <fcntl.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include "alloc-util.h"
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#include "def.h"
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#include "errno.h"
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#include "fd-util.h"
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#include "fileio.h"
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#include "mkdir.h"
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#include "nspawn-setuid.h"
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#include "process-util.h"
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#include "rlimit-util.h"
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#include "signal-util.h"
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#include "string-util.h"
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#include "strv.h"
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#include "user-util.h"
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#include "util.h"
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static int spawn_getent(const char *database, const char *key, pid_t *rpid) {
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int pipe_fds[2], r;
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pid_t pid;
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assert(database);
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assert(key);
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assert(rpid);
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if (pipe2(pipe_fds, O_CLOEXEC) < 0)
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return log_error_errno(errno, "Failed to allocate pipe: %m");
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r = safe_fork("(getent)", FORK_RESET_SIGNALS|FORK_DEATHSIG|FORK_LOG, &pid);
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if (r < 0) {
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safe_close_pair(pipe_fds);
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return r;
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}
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if (r == 0) {
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char *empty_env = NULL;
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safe_close(pipe_fds[0]);
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if (rearrange_stdio(-1, pipe_fds[1], -1) < 0)
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_exit(EXIT_FAILURE);
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(void) close_all_fds(NULL, 0);
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(void) rlimit_nofile_safe();
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execle("/usr/bin/getent", "getent", database, key, NULL, &empty_env);
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execle("/bin/getent", "getent", database, key, NULL, &empty_env);
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_exit(EXIT_FAILURE);
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}
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pipe_fds[1] = safe_close(pipe_fds[1]);
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*rpid = pid;
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return pipe_fds[0];
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}
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int change_uid_gid_raw(
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uid_t uid,
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gid_t gid,
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const gid_t *supplementary_gids,
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size_t n_supplementary_gids,
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bool chown_stdio) {
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if (!uid_is_valid(uid))
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uid = 0;
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if (!gid_is_valid(gid))
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gid = 0;
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if (chown_stdio) {
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(void) fchown(STDIN_FILENO, uid, gid);
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(void) fchown(STDOUT_FILENO, uid, gid);
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(void) fchown(STDERR_FILENO, uid, gid);
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}
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if (setgroups(n_supplementary_gids, supplementary_gids) < 0)
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return log_error_errno(errno, "Failed to set auxiliary groups: %m");
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if (setresgid(gid, gid, gid) < 0)
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return log_error_errno(errno, "setresgid() failed: %m");
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if (setresuid(uid, uid, uid) < 0)
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return log_error_errno(errno, "setresuid() failed: %m");
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return 0;
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}
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int change_uid_gid(const char *user, bool chown_stdio, char **ret_home) {
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char *x, *u, *g, *h;
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_cleanup_free_ gid_t *gids = NULL;
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_cleanup_free_ char *home = NULL, *line = NULL;
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_cleanup_fclose_ FILE *f = NULL;
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_cleanup_close_ int fd = -1;
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unsigned n_gids = 0;
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uid_t uid;
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gid_t gid;
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pid_t pid;
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int r;
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assert(ret_home);
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if (!user || STR_IN_SET(user, "root", "0")) {
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/* Reset everything fully to 0, just in case */
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r = reset_uid_gid();
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if (r < 0)
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return log_error_errno(r, "Failed to become root: %m");
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*ret_home = NULL;
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return 0;
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}
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/* First, get user credentials */
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fd = spawn_getent("passwd", user, &pid);
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if (fd < 0)
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return fd;
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f = take_fdopen(&fd, "r");
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if (!f)
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return log_oom();
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r = read_line(f, LONG_LINE_MAX, &line);
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if (r == 0)
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return log_error_errno(SYNTHETIC_ERRNO(ESRCH),
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"Failed to resolve user %s.", user);
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if (r < 0)
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return log_error_errno(r, "Failed to read from getent: %m");
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(void) wait_for_terminate_and_check("getent passwd", pid, WAIT_LOG);
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x = strchr(line, ':');
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if (!x)
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return log_error_errno(SYNTHETIC_ERRNO(EIO),
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"/etc/passwd entry has invalid user field.");
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u = strchr(x+1, ':');
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if (!u)
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return log_error_errno(SYNTHETIC_ERRNO(EIO),
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"/etc/passwd entry has invalid password field.");
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u++;
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g = strchr(u, ':');
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if (!g)
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return log_error_errno(SYNTHETIC_ERRNO(EIO),
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"/etc/passwd entry has invalid UID field.");
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*g = 0;
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g++;
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x = strchr(g, ':');
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if (!x)
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return log_error_errno(SYNTHETIC_ERRNO(EIO),
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"/etc/passwd entry has invalid GID field.");
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*x = 0;
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h = strchr(x+1, ':');
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if (!h)
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return log_error_errno(SYNTHETIC_ERRNO(EIO),
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"/etc/passwd entry has invalid GECOS field.");
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h++;
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x = strchr(h, ':');
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if (!x)
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return log_error_errno(SYNTHETIC_ERRNO(EIO),
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"/etc/passwd entry has invalid home directory field.");
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*x = 0;
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r = parse_uid(u, &uid);
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if (r < 0)
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return log_error_errno(SYNTHETIC_ERRNO(EIO),
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"Failed to parse UID of user.");
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r = parse_gid(g, &gid);
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if (r < 0)
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return log_error_errno(SYNTHETIC_ERRNO(EIO),
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"Failed to parse GID of user.");
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home = strdup(h);
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if (!home)
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return log_oom();
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f = safe_fclose(f);
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line = mfree(line);
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/* Second, get group memberships */
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fd = spawn_getent("initgroups", user, &pid);
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if (fd < 0)
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return fd;
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f = take_fdopen(&fd, "r");
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if (!f)
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return log_oom();
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r = read_line(f, LONG_LINE_MAX, &line);
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if (r == 0)
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return log_error_errno(SYNTHETIC_ERRNO(ESRCH),
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"Failed to resolve user %s.", user);
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if (r < 0)
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return log_error_errno(r, "Failed to read from getent: %m");
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(void) wait_for_terminate_and_check("getent initgroups", pid, WAIT_LOG);
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/* Skip over the username and subsequent separator whitespace */
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x = line;
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x += strcspn(x, WHITESPACE);
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x += strspn(x, WHITESPACE);
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for (const char *p = x;;) {
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_cleanup_free_ char *word = NULL;
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r = extract_first_word(&p, &word, NULL, 0);
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if (r < 0)
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return log_error_errno(r, "Failed to parse group data from getent: %m");
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if (r == 0)
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break;
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if (!GREEDY_REALLOC(gids, n_gids+1))
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return log_oom();
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r = parse_gid(word, &gids[n_gids++]);
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if (r < 0)
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return log_error_errno(r, "Failed to parse group data from getent: %m");
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}
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r = mkdir_parents(home, 0775);
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if (r < 0)
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return log_error_errno(r, "Failed to make home root directory: %m");
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r = mkdir_safe(home, 0755, uid, gid, 0);
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if (r < 0 && !IN_SET(r, -EEXIST, -ENOTDIR))
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return log_error_errno(r, "Failed to make home directory: %m");
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r = change_uid_gid_raw(uid, gid, gids, n_gids, chown_stdio);
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if (r < 0)
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return r;
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if (ret_home)
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*ret_home = TAKE_PTR(home);
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return 0;
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}
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