linux-kernel - Re: [PATCH] net: bpf_jit: fix BPF_S_ALU_AND

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Date:	Sat, 31 Mar 2012 12:23:04 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Indan Zupancic <indan@....nu>
Cc:	netdev@...r.kernel.org, stable@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: bpf_jit: fix BPF_S_ALU_AND_K compilation

On Sat, 2012-03-31 at 20:52 +1100, Indan Zupancic wrote:
> Hello,
> 
> Finally, after much searching I found one little bug.
> 
> [PATCH] net: bpf_jit: fix BPF_S_ALU_AND_K compilation
> 
> Small typo resulted in bad code generation for certain
> values of K for the BPF_S_ALU_AND_K instruction.
> 
> Signed-off-by: Indan Zupancic <indan@....nu>
> ---
> 
> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
> index 7c1b765..28bc807 100644
> --- a/arch/x86/net/bpf_jit_comp.c
> +++ b/arch/x86/net/bpf_jit_comp.c
> @@ -289,7 +289,7 @@ void bpf_jit_compile(struct sk_filter *fp)
>  					EMIT2(0x24, K & 0xFF); /* and imm8,%al */
>  				} else if (K >= 0xFFFF0000) {
>  					EMIT2(0x66, 0x25);	/* and imm16,%ax */
> -					EMIT2(K, 2);
> +					EMIT(K, 2);
>  				} else {
>  					EMIT1_off32(0x25, K);	/* and imm32,%eax */
>  				}
> 
> 

Thanks but it was already fixed.

commit 1d24fb3684f347226747c6b11ea426b7b992694e
Author: zhuangfeiran@....ac.cn <zhuangfeiran@....ac.cn>
Date:   Wed Mar 28 23:27:00 2012 +0000

    x86 bpf_jit: fix a bug in emitting the 16-bit immediate operand of AND
    
    When K >= 0xFFFF0000, AND needs the two least significant bytes of K as
    its operand, but EMIT2() gives it the least significant byte of K and
    0x2. EMIT() should be used here to replace EMIT2().
    
    Signed-off-by: Feiran Zhuang  <zhuangfeiran@....ac.cn>
    Acked-by: Eric Dumazet <eric.dumazet@...il.com>
    Signed-off-by: David S. Miller <davem@...emloft.net>



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