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Re: [PATCH 05/17] MIPS: bpf: Return error code if the offset is a negati

To: Markos Chandras <markos.chandras@imgtec.com>
Subject: Re: [PATCH 05/17] MIPS: bpf: Return error code if the offset is a negative number
From: Alexei Starovoitov <ast@plumgrid.com>
Date: Mon, 23 Jun 2014 15:09:01 -0700
Cc: Linux MIPS Mailing List <linux-mips@linux-mips.org>, "David S. Miller" <davem@davemloft.net>, Daniel Borkmann <dborkman@redhat.com>, Network Development <netdev@vger.kernel.org>
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On Mon, Jun 23, 2014 at 2:38 AM, Markos Chandras
<markos.chandras@imgtec.com> wrote:
> Previously, the negative offset was not checked leading to failures
> due to trying to load data beyond the skb struct boundaries. Until we
> have proper asm helpers in place, it's best if we return ENOSUPP if K
> is negative when trying to JIT the filter or 0 during runtime if we
> do an indirect load where the value of X is unknown during build time.
>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Daniel Borkmann <dborkman@redhat.com>
> Cc: Alexei Starovoitov <ast@plumgrid.com>
> Cc: netdev@vger.kernel.org
> Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>

Hi Markos,

thank you for addressing all of my earlier comments.
Looks like test_bpf was quite useful in finding all of these bugs :)
For the patches that reached netdev:

Acked-by: Alexei Starovoitov <ast@plumgrid.com>

One minor nit below:

> ---
>  arch/mips/net/bpf_jit.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
>
> diff --git a/arch/mips/net/bpf_jit.c b/arch/mips/net/bpf_jit.c
> index 5cc92c4590cb..95728ea6cb74 100644
> --- a/arch/mips/net/bpf_jit.c
> +++ b/arch/mips/net/bpf_jit.c
> @@ -331,6 +331,12 @@ static inline void emit_srl(unsigned int dst, unsigned 
> int src,
>         emit_instr(ctx, srl, dst, src, sa);
>  }
>
> +static inline void emit_slt(unsigned int dst, unsigned int src1,
> +                           unsigned int src2, struct jit_ctx *ctx)
> +{
> +       emit_instr(ctx, slt, dst, src1, src2);
> +}
> +
>  static inline void emit_sltu(unsigned int dst, unsigned int src1,
>                              unsigned int src2, struct jit_ctx *ctx)
>  {
> @@ -816,8 +822,21 @@ static int build_body(struct jit_ctx *ctx)
>                         /* A <- P[k:1] */
>                         load_order = 0;
>  load:
> +                       /* the interpreter will deal with the negative K */
> +                       if ((int)k < 0)

should be a space after cast.

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