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author | Andrey Ignatov <rdna@fb.com> | 2018-03-30 15:08:00 -0700 |
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committer | Daniel Borkmann <daniel@iogearbox.net> | 2018-03-31 02:14:44 +0200 |
commit | 5e43f899b03a3492ce5fc44e8900becb04dae9c0 (patch) | |
tree | 2811b77402c54e99a10a74f8a1b092b4bc2e24f6 /include | |
parent | 807ae7daf5fb9ba9ef688344ae7c0d8cbebd211c (diff) | |
download | linux-stable-5e43f899b03a3492ce5fc44e8900becb04dae9c0.tar.gz linux-stable-5e43f899b03a3492ce5fc44e8900becb04dae9c0.tar.bz2 linux-stable-5e43f899b03a3492ce5fc44e8900becb04dae9c0.zip |
bpf: Check attach type at prog load time
== The problem ==
There are use-cases when a program of some type can be attached to
multiple attach points and those attach points must have different
permissions to access context or to call helpers.
E.g. context structure may have fields for both IPv4 and IPv6 but it
doesn't make sense to read from / write to IPv6 field when attach point
is somewhere in IPv4 stack.
Same applies to BPF-helpers: it may make sense to call some helper from
some attach point, but not from other for same prog type.
== The solution ==
Introduce `expected_attach_type` field in in `struct bpf_attr` for
`BPF_PROG_LOAD` command. If scenario described in "The problem" section
is the case for some prog type, the field will be checked twice:
1) At load time prog type is checked to see if attach type for it must
be known to validate program permissions correctly. Prog will be
rejected with EINVAL if it's the case and `expected_attach_type` is
not specified or has invalid value.
2) At attach time `attach_type` is compared with `expected_attach_type`,
if prog type requires to have one, and, if they differ, attach will
be rejected with EINVAL.
The `expected_attach_type` is now available as part of `struct bpf_prog`
in both `bpf_verifier_ops->is_valid_access()` and
`bpf_verifier_ops->get_func_proto()` () and can be used to check context
accesses and calls to helpers correspondingly.
Initially the idea was discussed by Alexei Starovoitov <ast@fb.com> and
Daniel Borkmann <daniel@iogearbox.net> here:
https://marc.info/?l=linux-netdev&m=152107378717201&w=2
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'include')
-rw-r--r-- | include/linux/bpf.h | 5 | ||||
-rw-r--r-- | include/linux/filter.h | 1 | ||||
-rw-r--r-- | include/uapi/linux/bpf.h | 5 |
3 files changed, 10 insertions, 1 deletions
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 819229c80eca..95a7abd0ee92 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -208,12 +208,15 @@ struct bpf_prog_ops { struct bpf_verifier_ops { /* return eBPF function prototype for verification */ - const struct bpf_func_proto *(*get_func_proto)(enum bpf_func_id func_id); + const struct bpf_func_proto * + (*get_func_proto)(enum bpf_func_id func_id, + const struct bpf_prog *prog); /* return true if 'size' wide access at offset 'off' within bpf_context * with 'type' (read or write) is allowed */ bool (*is_valid_access)(int off, int size, enum bpf_access_type type, + const struct bpf_prog *prog, struct bpf_insn_access_aux *info); int (*gen_prologue)(struct bpf_insn *insn, bool direct_write, const struct bpf_prog *prog); diff --git a/include/linux/filter.h b/include/linux/filter.h index 897ff3d95968..13c044e4832d 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -469,6 +469,7 @@ struct bpf_prog { is_func:1, /* program is a bpf function */ kprobe_override:1; /* Do we override a kprobe? */ enum bpf_prog_type type; /* Type of BPF program */ + enum bpf_attach_type expected_attach_type; /* For some prog types */ u32 len; /* Number of filter blocks */ u32 jited_len; /* Size of jited insns in bytes */ u8 tag[BPF_TAG_SIZE]; diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 1878201c2d77..102718624d1e 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -296,6 +296,11 @@ union bpf_attr { __u32 prog_flags; char prog_name[BPF_OBJ_NAME_LEN]; __u32 prog_ifindex; /* ifindex of netdev to prep for */ + /* For some prog types expected attach type must be known at + * load time to verify attach type specific parts of prog + * (context accesses, allowed helpers, etc). + */ + __u32 expected_attach_type; }; struct { /* anonymous struct used by BPF_OBJ_* commands */ |