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[PATCH v2 3/5] ebpf: add a way to dump an eBPF program

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  [PATCH v2 3/5] ebpf: add a way to dump an eBPF program Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-11 02:30 +0200
    Re: [PATCH v2 3/5] ebpf: add a way to dump an eBPF program Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2015-09-11 04:30 +0200
      Re: [PATCH v2 3/5] ebpf: add a way to dump an eBPF program Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-11 17:00 +0200
    Re: [PATCH v2 3/5] ebpf: add a way to dump an eBPF program "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2015-09-11 14:20 +0200
    Re: [PATCH v2 3/5] ebpf: add a way to dump an eBPF program Daniel Borkmann <daniel@iogearbox.net> - 2015-09-11 15:40 +0200
      Re: [PATCH v2 3/5] ebpf: add a way to dump an eBPF program Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-11 16:50 +0200

#1222451 — [PATCH v2 3/5] ebpf: add a way to dump an eBPF program

This commit adds a way to dump eBPF programs. The initial implementation
doesn't support maps, and therefore only allows dumping seccomp ebpf
programs which themselves don't currently support maps.

v2: don't export a prog_id for the filter

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>
---
 include/uapi/linux/bpf.h | 14 ++++++++++++++
 kernel/bpf/syscall.c     | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 631cdee..e037a76 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -107,6 +107,13 @@ enum bpf_cmd {
 	 * returns fd or negative error
 	 */
 	BPF_PROG_LOAD,
+
+	/* dump an existing bpf
+	 * err = bpf(BPF_PROG_DUMP, union bpf_attr *attr, u32 size)
+	 * Using attr->prog_fd, attr->dump_insn_cnt, attr->dump_insns
+	 * returns zero or negative error
+	 */
+	BPF_PROG_DUMP,
 };
 
 enum bpf_map_type {
@@ -161,6 +168,13 @@ union bpf_attr {
 		__aligned_u64	log_buf;	/* user supplied buffer */
 		__u32		kern_version;	/* checked when prog_type=kprobe */
 	};
+
+	struct { /* anonymous struct used by BPF_PROG_DUMP command */
+		__u32		prog_fd;
+		__u32		dump_insn_cnt;
+		__aligned_u64	dump_insns;	/* user supplied buffer */
+		__u8		gpl_compatible;
+	};
 } __attribute__((aligned(8)));
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index dc9b464..58ae9f4 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -586,6 +586,44 @@ free_prog:
 	return err;
 }
 
+static int bpf_prog_dump(union bpf_attr *attr, union bpf_attr __user *uattr)
+{
+	int ufd = attr->prog_fd;
+	struct fd f = fdget(ufd);
+	struct bpf_prog *prog;
+	int ret = -EINVAL;
+
+	prog = get_prog(f);
+	if (IS_ERR(prog))
+		return PTR_ERR(prog);
+
+	/* For now, let's refuse to dump anything that isn't a seccomp program.
+	 * Other program types have support for maps, which our current dump
+	 * code doesn't support.
+	 */
+	if (prog->type != BPF_PROG_TYPE_SECCOMP)
+		goto out;
+
+	ret = -EFAULT;
+	if (put_user(prog->len, &uattr->dump_insn_cnt))
+		goto out;
+
+	if (put_user((u8) prog->gpl_compatible, &uattr->gpl_compatible))
+		goto out;
+
+	if (attr->dump_insns) {
+		u32 len = prog->len * sizeof(struct bpf_insn);
+
+		if (copy_to_user(u64_to_ptr(attr->dump_insns),
+				 prog->insns, len) != 0)
+			goto out;
+	}
+
+	ret = 0;
+out:
+	return ret;
+}
+
 SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)
 {
 	union bpf_attr attr = {};
@@ -650,6 +688,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
 	case BPF_PROG_LOAD:
 		err = bpf_prog_load(&attr);
 		break;
+	case BPF_PROG_DUMP:
+		err = bpf_prog_dump(&attr, uattr);
+		break;
 	default:
 		err = -EINVAL;
 		break;
-- 
2.1.4

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#1222495

On Thu, Sep 10, 2015 at 06:21:00PM -0600, Tycho Andersen wrote:
> +static int bpf_prog_dump(union bpf_attr *attr, union bpf_attr __user *uattr)
> +{
> +	int ufd = attr->prog_fd;
> +	struct fd f = fdget(ufd);
> +	struct bpf_prog *prog;
> +	int ret = -EINVAL;
> +
> +	prog = get_prog(f);
> +	if (IS_ERR(prog))
> +		return PTR_ERR(prog);
> +
> +	/* For now, let's refuse to dump anything that isn't a seccomp program.
> +	 * Other program types have support for maps, which our current dump
> +	 * code doesn't support.
> +	 */
> +	if (prog->type != BPF_PROG_TYPE_SECCOMP)
> +		goto out;
> +
> +	ret = -EFAULT;
> +	if (put_user(prog->len, &uattr->dump_insn_cnt))
> +		goto out;
> +
> +	if (put_user((u8) prog->gpl_compatible, &uattr->gpl_compatible))
> +		goto out;
> +
> +	if (attr->dump_insns) {
> +		u32 len = prog->len * sizeof(struct bpf_insn);
> +
> +		if (copy_to_user(u64_to_ptr(attr->dump_insns),
> +				 prog->insns, len) != 0)
> +			goto out;
> +	}
> +
> +	ret = 0;
> +out:
> +	return ret;

fdput() is missing in all error paths.

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#1222901

On Thu, Sep 10, 2015 at 07:29:42PM -0700, Alexei Starovoitov wrote:
> On Thu, Sep 10, 2015 at 06:21:00PM -0600, Tycho Andersen wrote:
> > +static int bpf_prog_dump(union bpf_attr *attr, union bpf_attr __user *uattr)
> > +{
> > +	int ufd = attr->prog_fd;
> > +	struct fd f = fdget(ufd);
> > +	struct bpf_prog *prog;
> > +	int ret = -EINVAL;
> > +
> > +	prog = get_prog(f);
> > +	if (IS_ERR(prog))
> > +		return PTR_ERR(prog);
> > +
> > +	/* For now, let's refuse to dump anything that isn't a seccomp program.
> > +	 * Other program types have support for maps, which our current dump
> > +	 * code doesn't support.
> > +	 */
> > +	if (prog->type != BPF_PROG_TYPE_SECCOMP)
> > +		goto out;
> > +
> > +	ret = -EFAULT;
> > +	if (put_user(prog->len, &uattr->dump_insn_cnt))
> > +		goto out;
> > +
> > +	if (put_user((u8) prog->gpl_compatible, &uattr->gpl_compatible))
> > +		goto out;
> > +
> > +	if (attr->dump_insns) {
> > +		u32 len = prog->len * sizeof(struct bpf_insn);
> > +
> > +		if (copy_to_user(u64_to_ptr(attr->dump_insns),
> > +				 prog->insns, len) != 0)
> > +			goto out;
> > +	}
> > +
> > +	ret = 0;
> > +out:
> > +	return ret;
> 
> fdput() is missing in all error paths.

So it is, thanks!

Tycho
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#1222769

Hi Tycho,

On 11 September 2015 at 02:21, Tycho Andersen
<tycho.andersen@canonical.com> wrote:
> This commit adds a way to dump eBPF programs. The initial implementation
> doesn't support maps, and therefore only allows dumping seccomp ebpf
> programs which themselves don't currently support maps.

Same broken record :-).

Cheers,

Michael


> v2: don't export a prog_id for the filter
>
> 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>
> ---
>  include/uapi/linux/bpf.h | 14 ++++++++++++++
>  kernel/bpf/syscall.c     | 41 +++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 55 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 631cdee..e037a76 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -107,6 +107,13 @@ enum bpf_cmd {
>          * returns fd or negative error
>          */
>         BPF_PROG_LOAD,
> +
> +       /* dump an existing bpf
> +        * err = bpf(BPF_PROG_DUMP, union bpf_attr *attr, u32 size)
> +        * Using attr->prog_fd, attr->dump_insn_cnt, attr->dump_insns
> +        * returns zero or negative error
> +        */
> +       BPF_PROG_DUMP,
>  };
>
>  enum bpf_map_type {
> @@ -161,6 +168,13 @@ union bpf_attr {
>                 __aligned_u64   log_buf;        /* user supplied buffer */
>                 __u32           kern_version;   /* checked when prog_type=kprobe */
>         };
> +
> +       struct { /* anonymous struct used by BPF_PROG_DUMP command */
> +               __u32           prog_fd;
> +               __u32           dump_insn_cnt;
> +               __aligned_u64   dump_insns;     /* user supplied buffer */
> +               __u8            gpl_compatible;
> +       };
>  } __attribute__((aligned(8)));
>
>  /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index dc9b464..58ae9f4 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -586,6 +586,44 @@ free_prog:
>         return err;
>  }
>
> +static int bpf_prog_dump(union bpf_attr *attr, union bpf_attr __user *uattr)
> +{
> +       int ufd = attr->prog_fd;
> +       struct fd f = fdget(ufd);
> +       struct bpf_prog *prog;
> +       int ret = -EINVAL;
> +
> +       prog = get_prog(f);
> +       if (IS_ERR(prog))
> +               return PTR_ERR(prog);
> +
> +       /* For now, let's refuse to dump anything that isn't a seccomp program.
> +        * Other program types have support for maps, which our current dump
> +        * code doesn't support.
> +        */
> +       if (prog->type != BPF_PROG_TYPE_SECCOMP)
> +               goto out;
> +
> +       ret = -EFAULT;
> +       if (put_user(prog->len, &uattr->dump_insn_cnt))
> +               goto out;
> +
> +       if (put_user((u8) prog->gpl_compatible, &uattr->gpl_compatible))
> +               goto out;
> +
> +       if (attr->dump_insns) {
> +               u32 len = prog->len * sizeof(struct bpf_insn);
> +
> +               if (copy_to_user(u64_to_ptr(attr->dump_insns),
> +                                prog->insns, len) != 0)
> +                       goto out;
> +       }
> +
> +       ret = 0;
> +out:
> +       return ret;
> +}
> +
>  SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)
>  {
>         union bpf_attr attr = {};
> @@ -650,6 +688,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
>         case BPF_PROG_LOAD:
>                 err = bpf_prog_load(&attr);
>                 break;
> +       case BPF_PROG_DUMP:
> +               err = bpf_prog_dump(&attr, uattr);
> +               break;
>         default:
>                 err = -EINVAL;
>                 break;
> --
> 2.1.4
>
> --
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-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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#1222850

On 09/11/2015 02:21 AM, Tycho Andersen wrote:
> This commit adds a way to dump eBPF programs. The initial implementation
> doesn't support maps, and therefore only allows dumping seccomp ebpf
> programs which themselves don't currently support maps.
>
> v2: don't export a prog_id for the filter
>
> 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>
[...]
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index dc9b464..58ae9f4 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -586,6 +586,44 @@ free_prog:
>   	return err;
>   }
>
> +static int bpf_prog_dump(union bpf_attr *attr, union bpf_attr __user *uattr)
> +{
> +	int ufd = attr->prog_fd;
> +	struct fd f = fdget(ufd);
> +	struct bpf_prog *prog;
> +	int ret = -EINVAL;
> +
> +	prog = get_prog(f);
> +	if (IS_ERR(prog))
> +		return PTR_ERR(prog);
> +
> +	/* For now, let's refuse to dump anything that isn't a seccomp program.
> +	 * Other program types have support for maps, which our current dump
> +	 * code doesn't support.
> +	 */
> +	if (prog->type != BPF_PROG_TYPE_SECCOMP)
> +		goto out;

Yep, also when you start adding helper calls (next to map objects) you'd
need to undo kernel pointers that the verifier sets here.
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#1222890

On Fri, Sep 11, 2015 at 03:39:14PM +0200, Daniel Borkmann wrote:
> On 09/11/2015 02:21 AM, Tycho Andersen wrote:
> >This commit adds a way to dump eBPF programs. The initial implementation
> >doesn't support maps, and therefore only allows dumping seccomp ebpf
> >programs which themselves don't currently support maps.
> >
> >v2: don't export a prog_id for the filter
> >
> >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>
> [...]
> >diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> >index dc9b464..58ae9f4 100644
> >--- a/kernel/bpf/syscall.c
> >+++ b/kernel/bpf/syscall.c
> >@@ -586,6 +586,44 @@ free_prog:
> >  	return err;
> >  }
> >
> >+static int bpf_prog_dump(union bpf_attr *attr, union bpf_attr __user *uattr)
> >+{
> >+	int ufd = attr->prog_fd;
> >+	struct fd f = fdget(ufd);
> >+	struct bpf_prog *prog;
> >+	int ret = -EINVAL;
> >+
> >+	prog = get_prog(f);
> >+	if (IS_ERR(prog))
> >+		return PTR_ERR(prog);
> >+
> >+	/* For now, let's refuse to dump anything that isn't a seccomp program.
> >+	 * Other program types have support for maps, which our current dump
> >+	 * code doesn't support.
> >+	 */
> >+	if (prog->type != BPF_PROG_TYPE_SECCOMP)
> >+		goto out;
> 
> Yep, also when you start adding helper calls (next to map objects) you'd
> need to undo kernel pointers that the verifier sets here.

Good point, I'll add that to the comment as well.

Tycho
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