chrootenv: small improvements
* Remove unused argument from pivot_root; * Factor out tmpdir creation into a separate function; * Remove unused fstype from bind mount; * Use unlink instead of a treewalk to remove empty temporary directory.
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e0d3bc292c
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@ -7,22 +7,16 @@
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#include <sched.h>
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#include <unistd.h>
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#define fail(s, err) g_error("%s: %s: %s", __func__, s, g_strerror(err))
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#define fail_if(expr) \
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if (expr) \
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fail(#expr, errno);
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#include <ftw.h>
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#include <sys/mount.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <sys/syscall.h>
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int min(int a, int b) {
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return a > b ? b : a;
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}
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#define fail(s, err) g_error("%s: %s: %s", __func__, s, g_strerror(err))
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#define fail_if(expr) \
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if (expr) \
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fail(#expr, errno);
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const gchar *bind_blacklist[] = {"bin", "etc", "host", "usr", "lib", "lib64", "lib32", "sbin", NULL};
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@ -36,10 +30,17 @@ void mount_tmpfs(const gchar *target) {
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void bind_mount(const gchar *source, const gchar *target) {
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fail_if(g_mkdir(target, 0755));
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fail_if(mount(source, target, "bind", MS_BIND | MS_REC, NULL));
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fail_if(mount(source, target, NULL, MS_BIND | MS_REC, NULL));
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}
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void pivot_host(const gchar *host, const gchar *guest) {
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const gchar *create_tmpdir() {
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gchar *prefix =
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g_build_filename(g_get_tmp_dir(), "chrootenvXXXXXX", NULL);
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fail_if(!g_mkdtemp_full(prefix, 0755));
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return prefix;
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}
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void pivot_host(const gchar *guest) {
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g_autofree gchar *point = g_build_filename(guest, "host", NULL);
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fail_if(g_mkdir(point, 0755));
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fail_if(pivot_root(guest, point));
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@ -68,7 +69,7 @@ void bind(const gchar *host, const gchar *guest) {
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if (!g_strv_contains(bind_blacklist, item))
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bind_mount_item(host, guest, item);
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pivot_host(host, guest);
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pivot_host(guest);
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}
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void spit(const char *path, char *fmt, ...) {
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@ -84,11 +85,6 @@ void spit(const char *path, char *fmt, ...) {
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fclose(f);
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}
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int nftw_remove(const char *path, const struct stat *sb, int type,
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struct FTW *ftw) {
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return remove(path);
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}
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int main(gint argc, gchar **argv) {
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const gchar *self = *argv++;
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@ -97,10 +93,7 @@ int main(gint argc, gchar **argv) {
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return 1;
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}
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g_autofree gchar *prefix =
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g_build_filename(g_get_tmp_dir(), "chrootenvXXXXXX", NULL);
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fail_if(!g_mkdtemp_full(prefix, 0755));
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g_autofree const gchar *prefix = create_tmpdir();
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pid_t cpid = fork();
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@ -136,10 +129,7 @@ int main(gint argc, gchar **argv) {
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int status;
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fail_if(waitpid(cpid, &status, 0) != cpid);
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// glibc 2.27 (and possibly other versions) can't handle
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// an nopenfd value larger than 2^19
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fail_if(nftw(prefix, nftw_remove, min(getdtablesize(), 1<<19),
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FTW_DEPTH | FTW_MOUNT | FTW_PHYS));
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fail_if(rmdir(prefix));
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if (WIFEXITED(status))
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return WEXITSTATUS(status);
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