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Merge pull request #2374 from brauner/2018-06-04/fix_remount_all_slave

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conf: copy mountinfo for remount_all_slave()
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Serge Hallyn 2018-06-04 09:36:43 -05:00 committed by GitHub
commit 2095b6d83a
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1 changed files with 56 additions and 3 deletions
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59
src/lxc/conf.c
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@ -43,6 +43,7 @@
#include <sys/mount.h>
#include <sys/param.h>
#include <sys/prctl.h>
#include <sys/sendfile.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/syscall.h>
@ -3178,14 +3179,63 @@ void tmp_proc_unmount(struct lxc_conf *lxc_conf)
/* Walk /proc/mounts and change any shared entries to slave. */
void remount_all_slave(void)
{
int memfd, mntinfo_fd, ret;
ssize_t copied;
FILE *f;
size_t len = 0;
char *line = NULL;
f = fopen("/proc/self/mountinfo", "r");
mntinfo_fd = open("/proc/self/mountinfo", O_RDONLY | O_CLOEXEC);
if (mntinfo_fd < 0)
return;
memfd = memfd_create(".lxc_mountinfo", MFD_CLOEXEC);
if (memfd < 0) {
char template[] = P_tmpdir "/.lxc_mountinfo_XXXXXX";
if (errno != ENOSYS) {
close(mntinfo_fd);
WARN("Failed to create temporary in-memory file");
return;
}
memfd = lxc_make_tmpfile(template, true);
}
if (memfd < 0) {
close(mntinfo_fd);
WARN("Failed to create temporary file");
return;
}
#define __LXC_SENDFILE_MAX 0x7ffff000 /* maximum number of bytes sendfile can handle */
again:
copied = sendfile(memfd, mntinfo_fd, NULL, __LXC_SENDFILE_MAX);
if (copied < 0) {
if (errno == EINTR)
goto again;
close(mntinfo_fd);
close(memfd);
WARN("Failed to copy \"/proc/self/mountinfo\"");
return;
}
close(mntinfo_fd);
/* After a successful fdopen() memfd will be closed when calling
* fclose(f). Calling close(memfd) afterwards is undefined.
*/
ret = lseek(memfd, 0, SEEK_SET);
if (ret < 0) {
close(memfd);
WARN("%s - Failed to reset file descriptor offset", strerror(errno));
return;
}
f = fdopen(memfd, "r");
if (!f) {
SYSERROR("Failed to open \"/proc/self/mountinfo\" to mark all shared");
ERROR("Continuing container startup...");
WARN("Failed to open copy of \"/proc/self/mountinfo\" to mark "
"all shared. Continuing");
close(memfd);
return;
}
@ -3210,10 +3260,13 @@ void remount_all_slave(void)
if (ret < 0) {
SYSERROR("Failed to make \"%s\" MS_SLAVE", target);
ERROR("Continuing...");
continue;
}
TRACE("Remounted \"%s\" as MS_SLAVE", target);
}
fclose(f);
free(line);
TRACE("Remounted all mount table entries as MS_SLAVE");
}
static int lxc_execute_bind_init(struct lxc_handler *handler)