mirror of
https://github.com/opencontainers/runc.git
synced 2026-04-23 07:21:09 +08:00
Brad Davidson
ccb589bd7d
This fixes k3s cross-compilation on Windows, broken by commit1912d5988b("*: actually support joining a userns with a new container"). [@kolyshkin: commit message] Fixes:1912d5988bSigned-off-by: Brad Davidson <brad.davidson@rancher.com> Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
82 lines
2.0 KiB
C
82 lines
2.0 KiB
C
//go:build linux
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#define _GNU_SOURCE
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#include <fcntl.h>
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#include <sched.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <stdarg.h>
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#include <stdlib.h>
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/*
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* All of the code here is run inside an aync-signal-safe context, so we need
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* to be careful to not call any functions that could cause issues. In theory,
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* since we are a Go program, there are fewer restrictions in practice, it's
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* better to be safe than sorry.
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*
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* The only exception is exit, which we need to call to make sure we don't
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* return into runc.
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*/
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void bail(int pipefd, const char *fmt, ...)
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{
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va_list args;
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va_start(args, fmt);
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vdprintf(pipefd, fmt, args);
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va_end(args);
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exit(1);
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}
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int spawn_userns_cat(char *userns_path, char *path, int outfd, int errfd)
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{
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char buffer[4096] = { 0 };
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pid_t child = fork();
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if (child != 0)
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return child;
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/* in child */
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/* Join the target userns. */
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int nsfd = open(userns_path, O_RDONLY);
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if (nsfd < 0)
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bail(errfd, "open userns path %s failed: %m", userns_path);
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int err = setns(nsfd, CLONE_NEWUSER);
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if (err < 0)
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bail(errfd, "setns %s failed: %m", userns_path);
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close(nsfd);
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/* Pipe the requested file contents. */
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int fd = open(path, O_RDONLY);
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if (fd < 0)
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bail(errfd, "open %s in userns %s failed: %m", path, userns_path);
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int nread, ntotal = 0;
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while ((nread = read(fd, buffer, sizeof(buffer))) != 0) {
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if (nread < 0)
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bail(errfd, "read bytes from %s failed (after %d total bytes read): %m", path, ntotal);
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ntotal += nread;
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int nwritten = 0;
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while (nwritten < nread) {
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int n = write(outfd, buffer, nread - nwritten);
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if (n < 0)
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bail(errfd, "write %d bytes from %s failed (after %d bytes written): %m",
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nread - nwritten, path, nwritten);
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nwritten += n;
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}
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if (nread != nwritten)
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bail(errfd, "mismatch for bytes read and written: %d read != %d written", nread, nwritten);
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}
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close(fd);
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close(outfd);
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close(errfd);
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/* We must exit here, otherwise we would return into a forked runc. */
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exit(0);
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}
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