[PATCH] arm64: bpf: fix out-of-bounds read in bpf2a64_offset()

[Alexei Starovoitov]

On 6/25/15 5:47 AM, Xi Wang wrote:
> Problems occur when bpf_to or bpf_from has value prog->len - 1 (e.g.,
> "Very long jump backwards" in test_bpf where the last instruction is a
> jump): since ctx->offset has length prog->len, ctx->offset[bpf_to + 1]
> or ctx->offset[bpf_from + 1] will cause an out-of-bounds read, leading
> to a bogus jump offset and kernel panic.
>
> This patch moves updating ctx->offset to after calling build_insn(),
> and changes indexing to use bpf_to and bpf_from without + 1.
>
> Cc: Zi Shen Lim<zlim.lnx at gmail.com>
> Cc: Alexei Starovoitov<ast at plumgrid.com>
> Cc: Will Deacon<will.deacon at arm.com>
> Fixes: e54bcde3d69d ("arm64: eBPF JIT compiler")
> Signed-off-by: Xi Wang<xi.wang at gmail.com>

Nice catch! Looks good to me.
Acked-by: Alexei Starovoitov <ast at plumgrid.com>