Introduce run_as for mkdir_recursive

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/lttng-sessiond/utils.c b/lttng-sessiond/utils.c
index fe1866ac7b9f72014e2ef12ead22065d3615ebee..489b61af8e1b744c5aac3117fb5b85a0b05cb732 100644 (file)
--- a/lttng-sessiond/utils.c
+++ b/lttng-sessiond/utils.c
@@ -22,6 +22,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/wait.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <unistd.h>
@@ -58,16 +59,14 @@ const char *get_home_dir(void)
 /*
  * Create recursively directory using the FULL path.
  */
-int mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid)
+static
+int _mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid)
 {
        int ret;
        char *p, tmp[PATH_MAX];
        size_t len;
        mode_t old_umask;
 
-       DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d", path, mode,
-                       uid, gid);
-
        ret = snprintf(tmp, sizeof(tmp), "%s", path);
        if (ret < 0) {
                PERROR("snprintf mkdir");
@@ -90,17 +89,6 @@ int mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid)
                                        ret = -errno;
                                        goto umask_error;
                                }
-                       } else if (ret == 0) {
-                               /*
-                                * We created the directory. Set its ownership to the
-                                * user/group specified.
-                                */
-                               ret = chown(tmp, uid, gid);
-                               if (ret < 0) {
-                                       PERROR("chown in mkdir recursive");
-                                       ret = -errno;
-                                       goto umask_error;
-                               }
                        }
                        *p = '/';
                }
@@ -114,17 +102,6 @@ int mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid)
                } else {
                        ret = 0;
                }
-       } else if (ret == 0) {
-               /*
-                * We created the directory. Set its ownership to the user/group
-                * specified.
-                */
-               ret = chown(tmp, uid, gid);
-               if (ret < 0) {
-                       PERROR("chown in mkdir recursive");
-                       ret = -errno;
-                       goto umask_error;
-               }
        }
 
 umask_error:
@@ -132,3 +109,67 @@ umask_error:
 error:
        return ret;
 }
+
+static
+int run_as(int (*cmd)(const char *path, mode_t mode, uid_t uid, gid_t gid),
+       const char *path, mode_t mode, uid_t uid, gid_t gid)
+{
+       int ret = 0;
+       pid_t pid;
+
+       /*
+        * If we are non-root, we can only deal with our own uid.
+        */
+       if (geteuid() != 0) {
+               if (uid != geteuid()) {
+                       ERR("Client (%d)/Server (%d) UID mismatch (and sessiond is not root)",
+                               uid, geteuid());
+                       return -EPERM;
+               }
+               return (*cmd)(path, mode, uid, gid);
+       }
+
+       pid = fork();
+       if (pid > 0) {
+               int status;
+
+               /*
+                * Parent: wait for child to return, in which case the
+                * shared memory map will have been created.
+                */
+               pid = wait(&status);
+               if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
+                       ret = -1;
+                       goto end;
+               }
+               goto end;
+       } else if (pid == 0) {
+               /* Child */
+               setegid(gid);
+               if (ret < 0) {
+                       perror("setegid");
+                       exit(EXIT_FAILURE);
+               }
+               ret = seteuid(uid);
+               if (ret < 0) {
+                       perror("seteuid");
+                       exit(EXIT_FAILURE);
+               }
+               ret = (*cmd)(path, mode, uid, gid);
+               if (!ret)
+                       exit(EXIT_SUCCESS);
+               else
+                       exit(EXIT_FAILURE);
+       } else {
+               return -1;
+       }
+end:
+       return ret;
+}
+
+int mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid)
+{
+       DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d",
+                       path, mode, uid, gid);
+       return run_as(_mkdir_recursive, path, mode, uid, gid);
+}