lkml.org 
[lkml]   [2016]   [Sep]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC v3 03/22] bpf,landlock: Add a new arraymap type to deal with (Landlock) handles
On Wed, Sep 14, 2016 at 09:23:56AM +0200, Mickaël Salaün wrote:
> This new arraymap looks like a set and brings new properties:
> * strong typing of entries: the eBPF functions get the array type of
> elements instead of CONST_PTR_TO_MAP (e.g.
> CONST_PTR_TO_LANDLOCK_HANDLE_FS);
> * force sequential filling (i.e. replace or append-only update), which
> allow quick browsing of all entries.
>
> This strong typing is useful to statically check if the content of a map
> can be passed to an eBPF function. For example, Landlock use it to store
> and manage kernel objects (e.g. struct file) instead of dealing with
> userland raw data. This improve efficiency and ensure that an eBPF
> program can only call functions with the right high-level arguments.
>
> The enum bpf_map_handle_type list low-level types (e.g.
> BPF_MAP_HANDLE_TYPE_LANDLOCK_FS_FD) which are identified when
> updating a map entry (handle). This handle types are used to infer a
> high-level arraymap type which are listed in enum bpf_map_array_type
> (e.g. BPF_MAP_ARRAY_TYPE_LANDLOCK_FS).
>
> For now, this new arraymap is only used by Landlock LSM (cf. next
> commits) but it could be useful for other needs.
>
> Changes since v2:
> * add a RLIMIT_NOFILE-based limit to the maximum number of arraymap
> handle entries (suggested by Andy Lutomirski)
> * remove useless checks
>
> Changes since v1:
> * arraymap of handles replace custom checker groups
> * simpler userland API
>
> Signed-off-by: Mickaël Salaün <mic@digikod.net>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Andy Lutomirski <luto@amacapital.net>
> Cc: Daniel Borkmann <daniel@iogearbox.net>
> Cc: David S. Miller <davem@davemloft.net>
> Cc: Kees Cook <keescook@chromium.org>
> Link: https://lkml.kernel.org/r/CALCETrWwTiz3kZTkEgOW24-DvhQq6LftwEXh77FD2G5o71yD7g@mail.gmail.com
> ---
> include/linux/bpf.h | 14 ++++
> include/uapi/linux/bpf.h | 18 +++++
> kernel/bpf/arraymap.c | 203 +++++++++++++++++++++++++++++++++++++++++++++++
> kernel/bpf/verifier.c | 12 ++-
> 4 files changed, 246 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index fa9a988400d9..eae4ce4542c1 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -13,6 +13,10 @@
> #include <linux/percpu.h>
> #include <linux/err.h>
>
> +#ifdef CONFIG_SECURITY_LANDLOCK
> +#include <linux/fs.h> /* struct file */
> +#endif /* CONFIG_SECURITY_LANDLOCK */
> +
> struct perf_event;
> struct bpf_map;
>
> @@ -38,6 +42,7 @@ struct bpf_map_ops {
> struct bpf_map {
> atomic_t refcnt;
> enum bpf_map_type map_type;
> + enum bpf_map_array_type map_array_type;
> u32 key_size;
> u32 value_size;
> u32 max_entries;
> @@ -187,6 +192,9 @@ struct bpf_array {
> */
> enum bpf_prog_type owner_prog_type;
> bool owner_jited;
> +#ifdef CONFIG_SECURITY_LANDLOCK
> + u32 n_entries; /* number of entries in a handle array */
> +#endif /* CONFIG_SECURITY_LANDLOCK */
> union {
> char value[0] __aligned(8);
> void *ptrs[0] __aligned(8);
> @@ -194,6 +202,12 @@ struct bpf_array {
> };
> };
>
> +#ifdef CONFIG_SECURITY_LANDLOCK
> +struct map_landlock_handle {
> + u32 type; /* enum bpf_map_handle_type */
> +};
> +#endif /* CONFIG_SECURITY_LANDLOCK */
> +
> #define MAX_TAIL_CALL_CNT 32
>
> struct bpf_event_entry {
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 7cd36166f9b7..b68de57f7ab8 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -87,6 +87,15 @@ enum bpf_map_type {
> BPF_MAP_TYPE_PERCPU_ARRAY,
> BPF_MAP_TYPE_STACK_TRACE,P_TYPE_CGROUP_ARRAY
> BPF_MAP_TYPE_CGROUP_ARRAY,
> + BPF_MAP_TYPE_LANDLOCK_ARRAY,
> +};
> +
> +enum bpf_map_array_type {
> + BPF_MAP_ARRAY_TYPE_UNSPEC,
> +};
> +
> +enum bpf_map_handle_type {
> + BPF_MAP_HANDLE_TYPE_UNSPEC,
> };

missing something. why it has to be special to have it's own
fd array implementation?
Please take a look how BPF_MAP_TYPE_PERF_EVENT_ARRAY,
BPF_MAP_TYPE_CGROUP_ARRAY and BPF_MAP_TYPE_PROG_ARRAY are done.
The all store objects into array map that user space passes via FD.
I think the same model should apply here.

\
 
 \ /
  Last update: 2016-09-17 09:59    [W:0.316 / U:0.408 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site