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mount: apply superblock flags from the userns daemon

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Superblock flags can be changed only an owner of the global CAP_SYS_ADMIN.

But it is posible to mount tmpfs with any flags.

travis-ci: success for Fix a few issues to dump/restore Docker containers with userns
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
This commit is contained in:
Andrei Vagin 2016-10-26 23:55:23 +03:00 committed by Pavel Emelyanov
parent 5cb1ce94fe
commit c64ebbcc44
1 changed files with 38 additions and 3 deletions
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41
criu/mount.c
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@ -1686,6 +1686,27 @@ static char *mnt_fsname(struct mount_info *mi)
return mi->fstype->name;
}
static int apply_sb_flags(void *args, int fd, pid_t pid)
{
int rst = -1, err = -1;
long flags = *(int *) args;
char path[PSFDS];
snprintf(path, sizeof(path), "/proc/self/fd/%d", fd);
if (pid != getpid() && switch_ns(pid, &mnt_ns_desc, &rst))
return -1;
err = mount(NULL, path, NULL, MS_REMOUNT | flags, NULL);
if (err)
pr_perror("Unable to remount %s", path);
if (rst >= 0 && restore_ns(rst, &mnt_ns_desc))
return -1;
return err;
}
static int do_new_mount(struct mount_info *mi)
{
unsigned long sflags = mi->sb_flags;
@ -1726,9 +1747,23 @@ static int do_new_mount(struct mount_info *mi)
}
if (!mi->is_ns_root && !mi->external && remount_ro) {
MS_REMOUNT | MS_RDONLY, NULL)) {
pr_perror("Unable to apply mount options");
return -1;
int fd;
fd = open(mi->mountpoint, O_PATH);
if (fd < 0) {
pr_perror("Unable to open %s\n", mi->mountpoint);
return -1;
}
sflags |= MS_RDONLY;
if (userns_call(apply_sb_flags, 0,
&sflags, sizeof(int), fd)) {
pr_perror("Unable to apply mount falgs %d for %s",
mi->sb_flags, mi->mountpoint);
close(fd);
return -1;
}
close(fd);
}
if (mflags && mount(NULL, mi->mountpoint, NULL,