Re: [RFC v3 22/22] samples/landlock: Add sandbox example

[Alexei Starovoitov]

On Wed, Sep 14, 2016 at 09:24:15AM +0200, Mickaël Salaün wrote:
> Add a basic sandbox tool to create a process isolated from some part of
> the system. This can depend of the current cgroup.
> 
> Example with the current process hierarchy (seccomp):
> 
>   $ ls /home
>   user1
>   $ LANDLOCK_ALLOWED='/bin:/lib:/usr:/tmp:/proc/self/fd/0' \
>       ./samples/landlock/sandbox /bin/sh -i
>   Launching a new sandboxed process.
>   $ ls /home
>   ls: cannot open directory '/home': Permission denied
> 
> Example with a cgroup:
> 
>   $ mkdir /sys/fs/cgroup/sandboxed
>   $ ls /home
>   user1
>   $ LANDLOCK_CGROUPS='/sys/fs/cgroup/sandboxed' \
>       LANDLOCK_ALLOWED='/bin:/lib:/usr:/tmp:/proc/self/fd/0' \
>       ./samples/landlock/sandbox
>   Ready to sandbox with cgroups.
>   $ ls /home
>   user1
>   $ echo $$ > /sys/fs/cgroup/sandboxed/cgroup.procs
>   $ ls /home
>   ls: cannot open directory '/home': Permission denied
> 
> Changes since v2:
> * use BPF_PROG_ATTACH for cgroup handling
> 
> Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx>
...
> +	struct bpf_insn hook_path[] = {
> +		/* specify an option, if any */
> +		BPF_MOV32_IMM(BPF_REG_1, 0),
> +		/* handles to compare with */
> +		BPF_LD_MAP_FD(BPF_REG_2, map_fs),
> +		BPF_MOV64_IMM(BPF_REG_3, BPF_MAP_ARRAY_OP_OR),
> +		/* hook argument (struct file) */
> +		BPF_LDX_MEM(BPF_DW, BPF_REG_4, BPF_REG_6, offsetof(struct
> +					landlock_data, args[0])),
> +		/* checker function */
> +		BPF_EMIT_CALL(BPF_FUNC_landlock_cmp_fs_beneath_with_struct_file),

the example is sweet!
Since only that helper is used, could you skip the other one
from the patches (for now) ?