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SubjectRe: [PATCH 2/2] ARM: net: bpf_jit_32: fix sp-relative load/stores offsets.
Am 06.12.2012 15:38, schrieb Nicolas Schichan:
> The offset must be multiplied by 4 to be sure to access the correct
> 32bit word in the stack scratch space.
>
> For instance, a store at scratch memory cell #1 was generating the
> following:
>
> st r4, [sp, #1]
>
> While the correct code for this is:
>
> st r4, [sp, #4]
>
> To reproduce the bug (assuming your system has a NIC with the mac
> address 52:54:00:12:34:56):
>
> echo 0 > /proc/sys/net/core/bpf_jit_enable
> tcpdump -ni eth0 "ether[1] + ether[2] - ether[3] * ether[4] - ether[5] \
> == -0x3AA" # this will capture packets as expected
>
> echo 1 > /proc/sys/net/core/bpf_jit_enable
> tcpdump -ni eth0 "ether[1] + ether[2] - ether[3] * ether[4] - ether[5] \
> == -0x3AA" # this will not.
>
> This bug was present since the original inclusion of bpf_jit for ARM
> (ddecdfce: ARM: 7259/3: net: JIT compiler for packet filters).
>
> Signed-off-by: Nicolas Schichan <nschichan@freebox.fr>
> ---
> arch/arm/net/bpf_jit_32.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
> index a64d349..b6f305e 100644
> --- a/arch/arm/net/bpf_jit_32.c
> +++ b/arch/arm/net/bpf_jit_32.c
> @@ -42,7 +42,7 @@
> #define r_skb_hl ARM_R8
>
> #define SCRATCH_SP_OFFSET 0
> -#define SCRATCH_OFF(k) (SCRATCH_SP_OFFSET + (k))
> +#define SCRATCH_OFF(k) (SCRATCH_SP_OFFSET + 4 * (k))
>
> #define SEEN_MEM ((1 << BPF_MEMWORDS) - 1)
> #define SEEN_MEM_WORD(k) (1 << (k))

Acked-by: Mircea Gherzan <mgherzan@gmail.com>


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