| From foo@baz Tue Jan 26 21:35:03 PST 2016 |
| From: Rabin Vincent <rabin@rab.in> |
| Date: Tue, 12 Jan 2016 20:17:08 +0100 |
| Subject: net: bpf: reject invalid shifts |
| |
| From: Rabin Vincent <rabin@rab.in> |
| |
| [ Upstream commit 229394e8e62a4191d592842cf67e80c62a492937 ] |
| |
| On ARM64, a BUG() is triggered in the eBPF JIT if a filter with a |
| constant shift that can't be encoded in the immediate field of the |
| UBFM/SBFM instructions is passed to the JIT. Since these shifts |
| amounts, which are negative or >= regsize, are invalid, reject them in |
| the eBPF verifier and the classic BPF filter checker, for all |
| architectures. |
| |
| Signed-off-by: Rabin Vincent <rabin@rab.in> |
| Acked-by: Alexei Starovoitov <ast@kernel.org> |
| Acked-by: Daniel Borkmann <daniel@iogearbox.net> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| kernel/bpf/verifier.c | 10 ++++++++++ |
| net/core/filter.c | 5 +++++ |
| 2 files changed, 15 insertions(+) |
| |
| --- a/kernel/bpf/verifier.c |
| +++ b/kernel/bpf/verifier.c |
| @@ -1058,6 +1058,16 @@ static int check_alu_op(struct reg_state |
| return -EINVAL; |
| } |
| |
| + if ((opcode == BPF_LSH || opcode == BPF_RSH || |
| + opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) { |
| + int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32; |
| + |
| + if (insn->imm < 0 || insn->imm >= size) { |
| + verbose("invalid shift %d\n", insn->imm); |
| + return -EINVAL; |
| + } |
| + } |
| + |
| /* pattern match 'bpf_add Rx, imm' instruction */ |
| if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 && |
| regs[insn->dst_reg].type == FRAME_PTR && |
| --- a/net/core/filter.c |
| +++ b/net/core/filter.c |
| @@ -781,6 +781,11 @@ static int bpf_check_classic(const struc |
| if (ftest->k == 0) |
| return -EINVAL; |
| break; |
| + case BPF_ALU | BPF_LSH | BPF_K: |
| + case BPF_ALU | BPF_RSH | BPF_K: |
| + if (ftest->k >= 32) |
| + return -EINVAL; |
| + break; |
| case BPF_LD | BPF_MEM: |
| case BPF_LDX | BPF_MEM: |
| case BPF_ST: |