seccomp, filter: add and use bpf_prog_create_from_user from seccomp

Seccomp has always been a special candidate when it comes to preparation
of its filters in seccomp_prepare_filter(). Due to the extra checks and
filter rewrite it partially duplicates code and has BPF internals exposed.

This patch adds a generic API inside the BPF code code that seccomp can use
and thus keep it's filter preparation code minimal and better maintainable.
The other side-effect is that now classic JITs can add seccomp support as
well by only providing a BPF_LDX | BPF_W | BPF_ABS translation.

Tested with seccomp and BPF test suites.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Nicolas Schichan <nschichan@freebox.fr>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Kees Cook <keescook@chromium.org>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 7 deletions

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 0dcb44bcfc5f..3c03a6085b82 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -374,19 +374,17 @@ static inline void bpf_prog_unlock_free(struct bpf_prog *fp)
 	__bpf_prog_free(fp);
 }
 
+typedef int (*bpf_aux_classic_check_t)(struct sock_filter *filter,
+				       unsigned int flen);
+
 int bpf_prog_create(struct bpf_prog **pfp, struct sock_fprog_kern *fprog);
+int bpf_prog_create_from_user(struct bpf_prog **pfp, struct sock_fprog *fprog,
+			      bpf_aux_classic_check_t trans);
 void bpf_prog_destroy(struct bpf_prog *fp);
 
 int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk);
 int sk_attach_bpf(u32 ufd, struct sock *sk);
 int sk_detach_filter(struct sock *sk);
-
-typedef int (*bpf_aux_classic_check_t)(struct sock_filter *filter,
-				       unsigned int flen);
-
-struct bpf_prog *bpf_prepare_filter(struct bpf_prog *fp,
-				    bpf_aux_classic_check_t trans);
-
 int sk_get_filter(struct sock *sk, struct sock_filter __user *filter,
 		  unsigned int len);