man/man2/mkdir.2: ERRORS: Add EOVERFLOW

mkdir(2) and mkdirat(2) might set errno to EOVERFLOW when UID or GID
mapping has not been configured.

Here's a small program that shows this behavior:

        #define _GNU_SOURCE
        #include <err.h>
        #include <sched.h>
        #include <stdlib.h>
        #include <sys/mman.h>
        #include <sys/mount.h>
        #include <sys/stat.h>
        #include <sys/wait.h>
        #include <unistd.h>

        static int
	childFunc(void *_)
        {
                if (mount("tmpfs", "/tmp", "tmpfs", 0, NULL))
                        err(EXIT_FAILURE, "mount");

                if (mkdir("/tmp/test", 0755) == -1)
                        err(EXIT_FAILURE, "mkdir");

                return 0;
        }

        #define STACK_SIZE (1024 * 1024)

        int
	main(void)
        {
                char   *stack; /* Start of stack buffer */
                char   *stackTop; /* End of stack buffer */
                pid_t  pid;

                stack = mmap(NULL, STACK_SIZE, PROT_READ | PROT_WRITE,
                             MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK,
                             -1, 0);
                if (stack == MAP_FAILED)
                        err(EXIT_FAILURE, "mmap");

                stackTop = stack + STACK_SIZE;

                pid = clone(childFunc, stackTop, CLONE_NEWUSER |
                            CLONE_NEWNS | SIGCHLD, NULL);
                if (munmap(stack, STACK_SIZE) == -1)
                        err(EXIT_FAILURE, "munmap");
                if (pid == -1)
                        err(EXIT_FAILURE, "clone");

                if (waitpid(pid, NULL, 0) == -1)
                        err(EXIT_FAILURE, "waitpid");

                exit(EXIT_SUCCESS);
        }

Link: <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=036d523641c66bef713042894a17f4335f199e49>
Signed-off-by: Chen Linxuan <chenlinxuan@uniontech.com>
Message-ID: <F22A2B1500170B63+20250202135733.11800-1-chenlinxuan@uniontech.com>
[alx: wfix]
Signed-off-by: Alejandro Colomar <alx@kernel.org>

diff --git a/man/man2/mkdir.2 b/man/man2/mkdir.2
index d84dbc27ebc41f48bd0ed9796f0eb298507fd0c8..3c3fad6eeff99427f90e516fa7e8eca46ad6bcfd 100644 (file)
--- a/man/man2/mkdir.2
+++ b/man/man2/mkdir.2
@@ -203,6 +203,10 @@ does not support the creation of directories.
 .B EROFS
 .I pathname
 refers to a file on a read-only filesystem.
+.B EOVERFLOW
+UID or GID mappings (see
+.BR user_namespaces (7))
+have not been configured.
 .SH VERSIONS
 Under Linux, apart from the permission bits, the
 .B S_ISVTX