On Fri, 2014-10-10 at 19:44 -0700, Alexei Starovoitov wrote:
> 2.
> while staring at the code realized that 64-byte buffer may not be enough
> when 1st insn is large, so increase it to 128 to avoid buffer overflow
> (theoretical maximum size of prologue+div is 109) and add runtime check.
>
> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
> index d56cd1f..8266896 100644
> --- a/arch/x86/net/bpf_jit_comp.c
> +++ b/arch/x86/net/bpf_jit_comp.c
> @@ -187,7 +187,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs,
> u8 *image,
> {
> struct bpf_insn *insn = bpf_prog->insnsi;
> int insn_cnt = bpf_prog->len;
> - u8 temp[64];
> + bool seen_ld_abs = ctx->seen_ld_abs | (oldproglen == 0);
> + u8 temp[128];
Hmmm. I would use some guard like :
#define BPF_MAX_INSN_SIZE 128
#define BPF_INSN_SAFETY 64
u8 temp[MAX_INSN_SIZE + BPF_INSN_SAFETY];
> + if (ilen >= sizeof(temp)) {
if (ilen > BPF_MAX_INSN_SIZE) {
...
> + pr_err("bpf_jit_compile fatal insn size error\n");
> + return -EFAULT;
> + }
> +
Otherwise, we might have corrupted stack and panic anyway.
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