Messages in this thread |  | | Subject | Re: [PATCH net] x86: bpf_jit: fix two bugs in eBPF JIT compiler | From | Eric Dumazet <> | Date | Fri, 10 Oct 2014 20:12:41 -0700 |
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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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