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chrootenv: small improvements

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* 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.
This commit is contained in:
Nikolay Amiantov 2019-05-11 11:32:47 +03:00
parent e0d3bc292c
commit 7664ffbbaf
1 changed files with 16 additions and 26 deletions
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42
pkgs/build-support/build-fhs-userenv/chrootenv/chrootenv.c
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@ -7,22 +7,16 @@
#include <sched.h>
#include <unistd.h>
#define fail(s, err) g_error("%s: %s: %s", __func__, s, g_strerror(err))
#define fail_if(expr) \
if (expr) \
fail(#expr, errno);
#include <ftw.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/syscall.h>
int min(int a, int b) {
return a > b ? b : a;
}
#define fail(s, err) g_error("%s: %s: %s", __func__, s, g_strerror(err))
#define fail_if(expr) \
if (expr) \
fail(#expr, errno);
const gchar *bind_blacklist[] = {"bin", "etc", "host", "usr", "lib", "lib64", "lib32", "sbin", NULL};
@ -36,10 +30,17 @@ void mount_tmpfs(const gchar *target) {
void bind_mount(const gchar *source, const gchar *target) {
fail_if(g_mkdir(target, 0755));
fail_if(mount(source, target, "bind", MS_BIND | MS_REC, NULL));
fail_if(mount(source, target, NULL, MS_BIND | MS_REC, NULL));
}
void pivot_host(const gchar *host, const gchar *guest) {
const gchar *create_tmpdir() {
gchar *prefix =
g_build_filename(g_get_tmp_dir(), "chrootenvXXXXXX", NULL);
fail_if(!g_mkdtemp_full(prefix, 0755));
return prefix;
}
void pivot_host(const gchar *guest) {
g_autofree gchar *point = g_build_filename(guest, "host", NULL);
fail_if(g_mkdir(point, 0755));
fail_if(pivot_root(guest, point));
@ -68,7 +69,7 @@ void bind(const gchar *host, const gchar *guest) {
if (!g_strv_contains(bind_blacklist, item))
bind_mount_item(host, guest, item);
pivot_host(host, guest);
pivot_host(guest);
}
void spit(const char *path, char *fmt, ...) {
@ -84,11 +85,6 @@ void spit(const char *path, char *fmt, ...) {
fclose(f);
}
int nftw_remove(const char *path, const struct stat *sb, int type,
struct FTW *ftw) {
return remove(path);
}
int main(gint argc, gchar **argv) {
const gchar *self = *argv++;
@ -97,10 +93,7 @@ int main(gint argc, gchar **argv) {
return 1;
}
g_autofree gchar *prefix =
g_build_filename(g_get_tmp_dir(), "chrootenvXXXXXX", NULL);
fail_if(!g_mkdtemp_full(prefix, 0755));
g_autofree const gchar *prefix = create_tmpdir();
pid_t cpid = fork();
@ -136,10 +129,7 @@ int main(gint argc, gchar **argv) {
int status;
fail_if(waitpid(cpid, &status, 0) != cpid);
// glibc 2.27 (and possibly other versions) can't handle
// an nopenfd value larger than 2^19
fail_if(nftw(prefix, nftw_remove, min(getdtablesize(), 1<<19),
FTW_DEPTH | FTW_MOUNT | FTW_PHYS));
fail_if(rmdir(prefix));
if (WIFEXITED(status))
return WEXITSTATUS(status);