attach: simplify lxc_attach_getpwshell()

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/src/lxc/attach.c b/src/lxc/attach.c
index afb4e0bc0fe12ea25aabcba87ced72ce48b412cb..9429d63876471cccefbede95181a8265c57d12f2 100644 (file)
--- a/src/lxc/attach.c
+++ b/src/lxc/attach.c
@@ -448,12 +448,15 @@ static char *lxc_attach_getpwshell(uid_t uid)
        int fd, ret;
        pid_t pid;
        int pipes[2];
-       char *result = NULL;
+       FILE *pipe_f;
+       bool found = false;
+       size_t line_bufsz = 0;
+       char *line = NULL, *result = NULL;
 
        /* We need to fork off a process that runs the getent program, and we
         * need to capture its output, so we use a pipe for that purpose.
         */
-       ret = pipe(pipes);
+       ret = pipe2(pipes, O_CLOEXEC);
        if (ret < 0)
                return NULL;
 
@@ -464,100 +467,7 @@ static char *lxc_attach_getpwshell(uid_t uid)
                return NULL;
        }
 
-       if (pid) {
-               int status;
-               FILE *pipe_f;
-               int found = 0;
-               size_t line_bufsz = 0;
-               char *line = NULL;
-
-               close(pipes[1]);
-
-               pipe_f = fdopen(pipes[0], "r");
-               while (getline(&line, &line_bufsz, pipe_f) != -1) {
-                       int i;
-                       long value;
-                       char *token;
-                       char *endptr = NULL, *saveptr = NULL;
-
-                       /* If we already found something, just continue to read
-                        * until the pipe doesn't deliver any more data, but
-                        * don't modify the existing data structure.
-                        */
-                       if (found)
-                               continue;
-
-                       /* Trim line on the right hand side. */
-                       for (i = strlen(line); i > 0 && (line[i - 1] == '\n' || line[i - 1] == '\r'); --i)
-                               line[i - 1] = '\0';
-
-                       /* Split into tokens: first: user name. */
-                       token = strtok_r(line, ":", &saveptr);
-                       if (!token)
-                               continue;
-                       /* next: dummy password field */
-                       token = strtok_r(NULL, ":", &saveptr);
-                       if (!token)
-                               continue;
-                       /* next: user id */
-                       token = strtok_r(NULL, ":", &saveptr);
-                       value = token ? strtol(token, &endptr, 10) : 0;
-                       if (!token || !endptr || *endptr || value == LONG_MIN || value == LONG_MAX)
-                               continue;
-                       /* dummy sanity check: user id matches */
-                       if ((uid_t) value != uid)
-                               continue;
-                       /* skip fields: gid, gecos, dir, go to next field 'shell' */
-                       for (i = 0; i < 4; i++) {
-                               token = strtok_r(NULL, ":", &saveptr);
-                               if (!token)
-                                       break;
-                       }
-                       if (!token)
-                               continue;
-                       free(result);
-                       result = strdup(token);
-
-                       /* Sanity check that there are no fields after that. */
-                       token = strtok_r(NULL, ":", &saveptr);
-                       if (token)
-                               continue;
-
-                       found = 1;
-               }
-
-               free(line);
-               fclose(pipe_f);
-       again:
-               if (waitpid(pid, &status, 0) < 0) {
-                       if (errno == EINTR)
-                               goto again;
-                       free(result);
-                       return NULL;
-               }
-
-               /* Some sanity checks. If anything even hinted at going wrong,
-                * we can't be sure we have a valid result, so we assume we
-                * don't.
-                */
-
-               if (!WIFEXITED(status)) {
-                       free(result);
-                       return NULL;
-               }
-
-               if (WEXITSTATUS(status) != 0) {
-                       free(result);
-                       return NULL;
-               }
-
-               if (!found) {
-                       free(result);
-                       return NULL;
-               }
-
-               return result;
-       } else {
+       if (!pid) {
                char uid_buf[32];
                char *arguments[] = {
                        "getent",
@@ -569,31 +479,108 @@ static char *lxc_attach_getpwshell(uid_t uid)
                close(pipes[0]);
 
                /* We want to capture stdout. */
-               dup2(pipes[1], 1);
+               ret = dup2(pipes[1], STDOUT_FILENO);
                close(pipes[1]);
+               if (ret < 0)
+                       exit(EXIT_FAILURE);
 
                /* Get rid of stdin/stderr, so we try to associate it with
                 * /dev/null.
                 */
-               fd = open("/dev/null", O_RDWR);
+               fd = open_devnull();
                if (fd < 0) {
-                       close(0);
-                       close(2);
+                       close(STDIN_FILENO);
+                       close(STDERR_FILENO);
                } else {
-                       dup2(fd, 0);
-                       dup2(fd, 2);
+                       (void)dup3(fd, STDIN_FILENO, O_CLOEXEC);
+                       (void)dup3(fd, STDOUT_FILENO, O_CLOEXEC);
                        close(fd);
                }
 
                /* Finish argument list. */
-               ret = snprintf(uid_buf, sizeof(uid_buf), "%ld", (long) uid);
-               if (ret <= 0)
-                       exit(-1);
+               ret = snprintf(uid_buf, sizeof(uid_buf), "%ld", (long)uid);
+               if (ret <= 0 || ret >= sizeof(uid_buf))
+                       exit(EXIT_FAILURE);
 
                /* Try to run getent program. */
-               (void) execvp("getent", arguments);
-               exit(-1);
+               (void)execvp("getent", arguments);
+               exit(EXIT_FAILURE);
        }
+
+       close(pipes[1]);
+
+       pipe_f = fdopen(pipes[0], "r");
+       while (getline(&line, &line_bufsz, pipe_f) != -1) {
+               int i;
+               long value;
+               char *token;
+               char *endptr = NULL, *saveptr = NULL;
+
+               /* If we already found something, just continue to read
+               * until the pipe doesn't deliver any more data, but
+               * don't modify the existing data structure.
+                */
+               if (found)
+                       continue;
+
+               /* Trim line on the right hand side. */
+               for (i = strlen(line); i > 0 && (line[i - 1] == '\n' || line[i - 1] == '\r'); --i)
+                       line[i - 1] = '\0';
+
+               /* Split into tokens: first: user name. */
+               token = strtok_r(line, ":", &saveptr);
+               if (!token)
+                       continue;
+
+               /* next: dummy password field */
+               token = strtok_r(NULL, ":", &saveptr);
+               if (!token)
+                       continue;
+
+               /* next: user id */
+               token = strtok_r(NULL, ":", &saveptr);
+               value = token ? strtol(token, &endptr, 10) : 0;
+               if (!token || !endptr || *endptr || value == LONG_MIN ||
+                               value == LONG_MAX)
+                       continue;
+
+               /* dummy sanity check: user id matches */
+               if ((uid_t)value != uid)
+                       continue;
+
+               /* skip fields: gid, gecos, dir, go to next field 'shell' */
+               for (i = 0; i < 4; i++) {
+                       token = strtok_r(NULL, ":", &saveptr);
+                       if (!token)
+                               continue;
+               }
+               if (!token)
+                       continue;
+               free(result);
+               result = strdup(token);
+
+               /* Sanity check that there are no fields after that. */
+               token = strtok_r(NULL, ":", &saveptr);
+               if (token)
+                       continue;
+
+               found = true;
+       }
+       free(line);
+       fclose(pipe_f);
+
+       ret = wait_for_pid(pid);
+       if (ret < 0) {
+               free(result);
+               return NULL;
+       }
+
+       if (!found) {
+               free(result);
+               return NULL;
+       }
+
+       return result;
 }
 
 static void lxc_attach_get_init_uidgid(uid_t *init_uid, gid_t *init_gid)