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Groups > linux.kernel > #1219146

[PATCH 6/6] ebpf: allow BPF_REG_X in src_reg conditional jumps

From Tycho Andersen <tycho.andersen@canonical.com>
Newsgroups linux.kernel
Subject [PATCH 6/6] ebpf: allow BPF_REG_X in src_reg conditional jumps
Date 2015-09-04 18:10 +0200
Message-ID <q51IT-70a-35@gated-at.bofh.it> (permalink)
References <q51IS-70a-7@gated-at.bofh.it>
Organization linux.* mail to news gateway

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The classic converter generates conditional jumps with:

if (BPF_SRC(fp->code) == BPF_K && (int) fp->k < 0) {
        ...
} else {
        insn->dst_reg = BPF_REG_A;
        insn->src_reg = BPF_REG_X;
        insn->imm = fp->k;
        bpf_src = BPF_SRC(fp->code);
}

but here, we enforce that the src_reg == BPF_REG_0. We should also allow
BPF_REG_X since that's what the converter generates; this enables us to
load eBPF programs that were generated by the converter.

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
CC: Kees Cook <keescook@chromium.org>
CC: Will Drewry <wad@chromium.org>
CC: Oleg Nesterov <oleg@redhat.com>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Pavel Emelyanov <xemul@parallels.com>
CC: Serge E. Hallyn <serge.hallyn@ubuntu.com>
CC: Alexei Starovoitov <ast@kernel.org>
CC: Daniel Borkmann <daniel@iogearbox.net>
---
 kernel/bpf/verifier.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 039d866..2fff8cd 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1080,7 +1080,12 @@ static int check_cond_jmp_op(struct verifier_env *env,
 		if (err)
 			return err;
 	} else {
-		if (insn->src_reg != BPF_REG_0) {
+		switch (insn->src_reg) {
+		case BPF_REG_0:
+		/* the classic converter generates BPF_JMP with src_reg of X */
+		case BPF_REG_X:
+			break;
+		default:
 			verbose("BPF_JMP uses reserved fields\n");
 			return -EINVAL;
 		}
-- 
2.1.4

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Thread

c/r of seccomp filters via underlying eBPF Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 18:10 +0200
  [PATCH 5/6] seccomp: add a way to attach a filter via eBPF fd Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 18:10 +0200
    Re: [PATCH 5/6] seccomp: add a way to attach a filter via eBPF fd Kees Cook <keescook@chromium.org> - 2015-09-04 22:50 +0200
      Re: [PATCH 5/6] seccomp: add a way to attach a filter via eBPF fd "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2015-09-05 09:20 +0200
    Re: [PATCH 5/6] seccomp: add a way to attach a filter via eBPF fd Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2015-09-04 22:50 +0200
  [PATCH 4/6] seccomp: add a way to access filters via bpf fds Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 18:10 +0200
    Re: [PATCH 4/6] seccomp: add a way to access filters via bpf fds Kees Cook <keescook@chromium.org> - 2015-09-04 22:30 +0200
      Re: [PATCH 4/6] seccomp: add a way to access filters via bpf fds Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2015-09-04 22:40 +0200
        Re: [PATCH 4/6] seccomp: add a way to access filters via bpf fds Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 23:00 +0200
  [PATCH 6/6] ebpf: allow BPF_REG_X in src_reg conditional jumps Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 18:10 +0200
    Re: [PATCH 6/6] ebpf: allow BPF_REG_X in src_reg conditional jumps Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2015-09-04 23:10 +0200
      Re: [PATCH 6/6] ebpf: allow BPF_REG_X in src_reg conditional jumps Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-05 00:50 +0200
        Re: [PATCH 6/6] ebpf: allow BPF_REG_X in src_reg conditional jumps Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2015-09-05 06:20 +0200
  [PATCH 1/6] ebpf: add a seccomp program type Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 18:10 +0200
    Re: [PATCH 1/6] ebpf: add a seccomp program type Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2015-09-04 22:20 +0200
      Re: [PATCH 1/6] ebpf: add a seccomp program type Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 23:10 +0200
    Re: [PATCH 1/6] ebpf: add a seccomp program type Kees Cook <keescook@chromium.org> - 2015-09-04 22:40 +0200
      Re: [PATCH 1/6] ebpf: add a seccomp program type Kees Cook <keescook@chromium.org> - 2015-09-04 23:10 +0200
      Re: [PATCH 1/6] ebpf: add a seccomp program type Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 23:10 +0200
    Re: [PATCH 1/6] ebpf: add a seccomp program type Andy Lutomirski <luto@amacapital.net> - 2015-09-05 00:00 +0200
  [PATCH 3/6] ebpf: add a way to dump an eBPF program Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 18:10 +0200
    Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Kees Cook <keescook@chromium.org> - 2015-09-04 22:20 +0200
      Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 22:50 +0200
        Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2015-09-04 23:00 +0200
          Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 23:10 +0200
        Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Kees Cook <keescook@chromium.org> - 2015-09-04 23:00 +0200
        Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Andy Lutomirski <luto@amacapital.net> - 2015-09-04 23:50 +0200
          Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-05 00:30 +0200
            Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Andy Lutomirski <luto@amacapital.net> - 2015-09-05 01:10 +0200
              Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-05 02:30 +0200
            Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Kees Cook <keescook@chromium.org> - 2015-09-05 01:30 +0200
              Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Andy Lutomirski <luto@amacapital.net> - 2015-09-05 02:10 +0200
    Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2015-09-04 22:30 +0200
      Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 22:50 +0200

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