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Fix idmapped mount layer on intercepted mounts #12484

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merged 3 commits into from
Oct 31, 2023
Merged

Fix idmapped mount layer on intercepted mounts #12484

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af10cb5
lxd/seccomp: Switch to path/filepath
stgraber Oct 27, 2023
67b8a1a
lxd/seccomp: Pass correct path and fstype to IdmappedStorage
stgraber Oct 27, 2023
0e54f20
lxd/forksyscall: Fix idmapped mount code path
stgraber Oct 27, 2023
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24 changes: 23 additions & 1 deletion lxd/main_forksyscall.go
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Original file line number Diff line number Diff line change
Expand Up @@ -441,9 +441,31 @@ static void mount_emulate(void)
_exit(EXIT_FAILURE);
} else if (strcmp(shiftfs, "idmapped") == 0) {
int fd_tree;
int fs_fd = -EBADF;

fd_tree = mount_detach_idmap(source, fd_userns);
struct lxc_mount_attr attr = {
.attr_set = MOUNT_ATTR_IDMAP,
};

fs_fd = lxd_fsopen(fstype, FSOPEN_CLOEXEC);
if (fs_fd < 0)
die("error: failed to create detached idmapped mount: fsopen");

ret = lxd_fsconfig(fs_fd, FSCONFIG_SET_STRING, "source", source, 0);
if (ret < 0)
die("error: failed to create detached idmapped mount: fsconfig");

ret = lxd_fsconfig(fs_fd, FSCONFIG_CMD_CREATE, NULL, NULL, 0);
if (ret < 0)
die("error: failed to create detached idmapped mount: fsconfig");

fd_tree = lxd_fsmount(fs_fd, FSMOUNT_CLOEXEC, flags);
if (fd_tree < 0)
die("error: failed to create detached idmapped mount: fsmount");

attr.userns_fd = fd_userns;
ret = lxd_mount_setattr(fd_tree, "", AT_EMPTY_PATH, &attr, sizeof(attr));
if (ret < 0)
die("error: failed to create detached idmapped mount");

ret = setns(fd_mntns, CLONE_NEWNS);
Expand Down
17 changes: 12 additions & 5 deletions lxd/seccomp/seccomp.go
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Original file line number Diff line number Diff line change
Expand Up @@ -449,7 +449,7 @@ import (
"io"
"net"
"os"
"path"
"path/filepath"
"regexp"
"runtime"
"strconv"
Expand Down Expand Up @@ -624,7 +624,7 @@ var seccompPath = shared.VarPath("security", "seccomp")

// ProfilePath returns the seccomp path for the instance.
func ProfilePath(c Instance) string {
return path.Join(seccompPath, project.Instance(c.Project().Name, c.Name()))
return filepath.Join(seccompPath, project.Instance(c.Project().Name, c.Name()))
}

// InstanceNeedsPolicy returns whether the instance needs a policy or not.
Expand Down Expand Up @@ -2070,7 +2070,6 @@ func (s *Server) HandleMountSyscall(c Instance, siov *Iovec) int {
}
args.source = C.GoString(&mntSource[0])
ctx["source"] = args.source
args.idmapType = s.MountSyscallShift(c, args.source)

// const char *target
if siov.req.data.args[1] != 0 {
Expand Down Expand Up @@ -2098,6 +2097,14 @@ func (s *Server) HandleMountSyscall(c Instance, siov *Iovec) int {
args.fstype = C.GoString(&mntFs[0])
ctx["fstype"] = args.fstype

// idmap shift
fullSrcPath := filepath.Join(fmt.Sprintf("/proc/%d/root/", args.pid), args.source)
if shared.PathExists(fullSrcPath) {
args.idmapType = s.MountSyscallShift(c, fullSrcPath, args.fstype)
} else {
args.idmapType = s.MountSyscallShift(c, args.source, args.fstype)
}

// unsigned long mountflags
args.flags = int(siov.req.data.args[3])

Expand Down Expand Up @@ -2469,15 +2476,15 @@ func (s *Server) MountSyscallValid(c Instance, args *MountArgs) (bool, string) {
}

// MountSyscallShift checks whether this mount syscall needs shiftfs.
func (s *Server) MountSyscallShift(c Instance, path string) idmap.IdmapStorageType {
func (s *Server) MountSyscallShift(c Instance, path string, fsType string) idmap.IdmapStorageType {
if shared.IsTrue(c.ExpandedConfig()["security.syscalls.intercept.mount.shift"]) {
diskIdmap, err := c.DiskIdmap()
if err != nil {
return idmap.IdmapStorageNone
}

if diskIdmap == nil {
return c.IdmappedStorage(path, "none")
return c.IdmappedStorage(path, fsType)
}
}

Expand Down
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