attach: fix namespace preservation

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

diff --git a/src/lxc/attach.c b/src/lxc/attach.c
index 20a59e6215b94115d464546f98bcb60f00e1ccf0..b86a5412d38b66e99a0d343d00ecf0f243889f68 100644 (file)
--- a/src/lxc/attach.c
+++ b/src/lxc/attach.c
@@ -487,16 +487,16 @@ static int same_nsfd(int dfd_pid1, int dfd_pid2, const char *ns_path)
 
        ret = fstatat(dfd_pid1, ns_path, &ns_st1, 0);
        if (ret)
-               return -1;
+               return -errno;
 
        ret = fstatat(dfd_pid2, ns_path, &ns_st2, 0);
        if (ret)
-               return -1;
+               return -errno;
 
        /* processes are in the same namespace */
        if ((ns_st1.st_dev == ns_st2.st_dev) &&
            (ns_st1.st_ino == ns_st2.st_ino))
-               return -EINVAL;
+               return 1;
 
        return 0;
 }
@@ -510,19 +510,23 @@ static int same_ns(int dfd_pid1, int dfd_pid2, const char *ns_path)
                         (PROTECT_LOOKUP_BENEATH_WITH_MAGICLINKS &
                          ~(RESOLVE_NO_XDEV | RESOLVE_BENEATH)), 0);
        if (ns_fd2 < 0) {
-               /* The kernel does not support this namespace. This is not an error. */
                if (errno == ENOENT)
                        return -ENOENT;
-               return log_error_errno(-errno, errno, "Failed to open %d(%s)",
-                                      dfd_pid2, ns_path);
+               return syserrno(-errno, "Failed to open %d(%s)", dfd_pid2, ns_path);
        }
 
        ret = same_nsfd(dfd_pid1, dfd_pid2, ns_path);
-       if (ret < 0)
-               return ret;
+       switch (ret) {
+       case -ENOENT:
+               __fallthrough;
+       case 1:
+               return ret_errno(ENOENT);
+       case 0:
+               /* processes are in different namespaces */
+               return move_fd(ns_fd2);
+       }
 
-       /* processes are in different namespaces */
-       return move_fd(ns_fd2);
+       return ret;
 }
 
 static int __prepare_namespaces_pidfd(struct attach_context *ctx)
@@ -536,14 +540,19 @@ static int __prepare_namespaces_pidfd(struct attach_context *ctx)
                ret = same_nsfd(ctx->dfd_self_pid,
                                ctx->dfd_init_pid,
                                ns_info[i].proc_path);
-               if (ret == -EINVAL)
+               switch (ret) {
+               case -ENOENT:
+                       __fallthrough;
+               case 1:
                        ctx->ns_inherited &= ~ns_info[i].clone_flag;
-               else if (ret < 0)
-                       return log_error_errno(-1, errno,
-                                              "Failed to determine whether %s namespace is shared",
-                                              ns_info[i].proc_name);
-               else
+                       break;
+               case 0:
                        TRACE("Shared %s namespace needs attach", ns_info[i].proc_name);
+                       break;
+               }
+
+               return syserrno(-errno, "Failed to determine whether %s namespace is shared",
+                               ns_info[i].proc_name);
        }
 
        return 0;