linux-kernel - Re: [PATCH v2] bpf, arm32: Correct check

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Date:   Fri, 25 May 2018 15:47:59 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Wang YanQing <udknight@...il.com>, linux@...linux.org.uk,
        ast@...com, illusionist.neo@...il.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] bpf, arm32: Correct check_imm24

On 05/11/2018 05:06 AM, Wang YanQing wrote:
> imm24 is signed, so the right range is:
> [-(1<<(24 - 1)), (1<<(24 - 1)) - 1]
> 
> Note:this patch also fix a typo.
> 
> Signed-off-by: Wang YanQing <udknight@...il.com>

Through which tree will this fix be routed? (And the cleanup in "[PATCH v2]
bpf, arm32: Fix inconsistent naming about emit_a32_lsr_r64|emit_a32_lsr_i64"?)
Wasn't fully clear from the subject in the patch whether target are bpf trees.

If this one here should go as a fix via bpf tree, would be great to get an
ACK from Russell.

Just asking since I haven't seen it in Linus' tree and it's been two weeks
by now, so making sure it's not getting lost in the archives. ;-)

> ---
>  Changes
>  v1-v2:
>  1:Rewrite the patch, I make a mistake, the v1 is wrong totally,
>    reported by Russell King.
> 
>    I use the fix suggested by Russell King instead of myself which
>    use the exact number range [-8388608, 8388607].
>  2:Fix the error in changelog.
> 
>  Thanks!
> 
>  arch/arm/net/bpf_jit_32.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
> index caccc78..316bc08 100644
> --- a/arch/arm/net/bpf_jit_32.c
> +++ b/arch/arm/net/bpf_jit_32.c
> @@ -84,7 +84,7 @@
>   *
>   * 1. First argument is passed using the arm 32bit registers and rest of the
>   * arguments are passed on stack scratch space.
> - * 2. First callee-saved arugument is mapped to arm 32 bit registers and rest
> + * 2. First callee-saved argument is mapped to arm 32 bit registers and rest
>   * arguments are mapped to scratch space on stack.
>   * 3. We need two 64 bit temp registers to do complex operations on eBPF
>   * registers.
> @@ -1199,8 +1199,8 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx)
>  	s32 jmp_offset;
>  
>  #define check_imm(bits, imm) do {				\
> -	if ((((imm) > 0) && ((imm) >> (bits))) ||		\
> -	    (((imm) < 0) && (~(imm) >> (bits)))) {		\
> +	if ((imm) >= (1 << ((bits) - 1)) ||			\
> +	    (imm) < -(1 << ((bits) - 1))) {			\
>  		pr_info("[%2d] imm=%d(0x%x) out of range\n",	\
>  			i, imm, imm);				\
>  		return -EINVAL;					\
>