diff options
author | Alexei Starovoitov <ast@plumgrid.com> | 2014-12-01 15:06:34 -0800 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2014-12-05 21:47:32 -0800 |
commit | ddd872bc3098f9d9abe1680a6b2013e59e3337f7 (patch) | |
tree | be98ca10e99f38fc5f84e94bacee95db64183b15 | |
parent | f51a5e82ea9aaf05106c00d976e772ca384a9199 (diff) | |
download | op-kernel-dev-ddd872bc3098f9d9abe1680a6b2013e59e3337f7.zip op-kernel-dev-ddd872bc3098f9d9abe1680a6b2013e59e3337f7.tar.gz |
bpf: verifier: add checks for BPF_ABS | BPF_IND instructions
introduce program type BPF_PROG_TYPE_SOCKET_FILTER that is used
for attaching programs to sockets where ctx == skb.
add verifier checks for ABS/IND instructions which can only be seen
in socket filters, therefore the check:
if (env->prog->aux->prog_type != BPF_PROG_TYPE_SOCKET_FILTER)
verbose("BPF_LD_ABS|IND instructions are only allowed in socket filters\n");
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r-- | include/uapi/linux/bpf.h | 1 | ||||
-rw-r--r-- | kernel/bpf/verifier.c | 70 |
2 files changed, 69 insertions, 2 deletions
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 4a3d0f8..45da7ec 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -117,6 +117,7 @@ enum bpf_map_type { enum bpf_prog_type { BPF_PROG_TYPE_UNSPEC, + BPF_PROG_TYPE_SOCKET_FILTER, }; /* flags for BPF_MAP_UPDATE_ELEM command */ diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index b6a1f7c..a28e09c 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1172,6 +1172,70 @@ static int check_ld_imm(struct verifier_env *env, struct bpf_insn *insn) return 0; } +/* verify safety of LD_ABS|LD_IND instructions: + * - they can only appear in the programs where ctx == skb + * - since they are wrappers of function calls, they scratch R1-R5 registers, + * preserve R6-R9, and store return value into R0 + * + * Implicit input: + * ctx == skb == R6 == CTX + * + * Explicit input: + * SRC == any register + * IMM == 32-bit immediate + * + * Output: + * R0 - 8/16/32-bit skb data converted to cpu endianness + */ +static int check_ld_abs(struct verifier_env *env, struct bpf_insn *insn) +{ + struct reg_state *regs = env->cur_state.regs; + u8 mode = BPF_MODE(insn->code); + struct reg_state *reg; + int i, err; + + if (env->prog->aux->prog_type != BPF_PROG_TYPE_SOCKET_FILTER) { + verbose("BPF_LD_ABS|IND instructions are only allowed in socket filters\n"); + return -EINVAL; + } + + if (insn->dst_reg != BPF_REG_0 || insn->off != 0 || + (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) { + verbose("BPF_LD_ABS uses reserved fields\n"); + return -EINVAL; + } + + /* check whether implicit source operand (register R6) is readable */ + err = check_reg_arg(regs, BPF_REG_6, SRC_OP); + if (err) + return err; + + if (regs[BPF_REG_6].type != PTR_TO_CTX) { + verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n"); + return -EINVAL; + } + + if (mode == BPF_IND) { + /* check explicit source operand */ + err = check_reg_arg(regs, insn->src_reg, SRC_OP); + if (err) + return err; + } + + /* reset caller saved regs to unreadable */ + for (i = 0; i < CALLER_SAVED_REGS; i++) { + reg = regs + caller_saved[i]; + reg->type = NOT_INIT; + reg->imm = 0; + } + + /* mark destination R0 register as readable, since it contains + * the value fetched from the packet + */ + regs[BPF_REG_0].type = UNKNOWN_VALUE; + return 0; +} + /* non-recursive DFS pseudo code * 1 procedure DFS-iterative(G,v): * 2 label v as discovered @@ -1677,8 +1741,10 @@ process_bpf_exit: u8 mode = BPF_MODE(insn->code); if (mode == BPF_ABS || mode == BPF_IND) { - verbose("LD_ABS is not supported yet\n"); - return -EINVAL; + err = check_ld_abs(env, insn); + if (err) + return err; + } else if (mode == BPF_IMM) { err = check_ld_imm(env, insn); if (err) |