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bpf: verifier: randomize high 32-bit when BPF_F_TEST_RND_HI32 is set 

This patch randomizes high 32-bit of a definition when BPF_F_TEST_RND_HI32
is set.

Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Jiong Wang 2019-05-24 23:25:18 +01:00 committed by Alexei Starovoitov
parent 9ce33e337f
commit d6c2308c74
1 changed files with 57 additions and 11 deletions
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68
kernel/bpf/verifier.c
View File

@ -7640,33 +7640,79 @@ static int opt_remove_nops(struct bpf_verifier_env *env)
return 0;
}
static int opt_subreg_zext_lo32(struct bpf_verifier_env *env)
static int opt_subreg_zext_lo32_rnd_hi32(struct bpf_verifier_env *env,
const union bpf_attr *attr)
{
struct bpf_insn *patch, zext_patch[2], rnd_hi32_patch[4];
struct bpf_insn_aux_data *aux = env->insn_aux_data;
int i, patch_len, delta = 0, len = env->prog->len;
struct bpf_insn *insns = env->prog->insnsi;
int i, delta = 0, len = env->prog->len;
struct bpf_insn zext_patch[2];
struct bpf_prog *new_prog;
bool rnd_hi32;
rnd_hi32 = attr->prog_flags & BPF_F_TEST_RND_HI32;
zext_patch[1] = BPF_ZEXT_REG(0);
rnd_hi32_patch[1] = BPF_ALU64_IMM(BPF_MOV, BPF_REG_AX, 0);
rnd_hi32_patch[2] = BPF_ALU64_IMM(BPF_LSH, BPF_REG_AX, 32);
rnd_hi32_patch[3] = BPF_ALU64_REG(BPF_OR, 0, BPF_REG_AX);
for (i = 0; i < len; i++) {
int adj_idx = i + delta;
struct bpf_insn insn;
if (!aux[adj_idx].zext_dst)
insn = insns[adj_idx];
if (!aux[adj_idx].zext_dst) {
u8 code, class;
u32 imm_rnd;
if (!rnd_hi32)
continue;
code = insn.code;
class = BPF_CLASS(code);
if (insn_no_def(&insn))
continue;
/* NOTE: arg "reg" (the fourth one) is only used for
* BPF_STX which has been ruled out in above
* check, it is safe to pass NULL here.
*/
if (is_reg64(env, &insn, insn.dst_reg, NULL, DST_OP)) {
if (class == BPF_LD &&
BPF_MODE(code) == BPF_IMM)
i++;
continue;
}
/* ctx load could be transformed into wider load. */
if (class == BPF_LDX &&
aux[adj_idx].ptr_type == PTR_TO_CTX)
continue;
imm_rnd = get_random_int();
rnd_hi32_patch[0] = insn;
rnd_hi32_patch[1].imm = imm_rnd;
rnd_hi32_patch[3].dst_reg = insn.dst_reg;
patch = rnd_hi32_patch;
patch_len = 4;
goto apply_patch_buffer;
}
if (!bpf_jit_needs_zext())
continue;
insn = insns[adj_idx];
zext_patch[0] = insn;
zext_patch[1].dst_reg = insn.dst_reg;
zext_patch[1].src_reg = insn.dst_reg;
new_prog = bpf_patch_insn_data(env, adj_idx, zext_patch, 2);
patch = zext_patch;
patch_len = 2;
apply_patch_buffer:
new_prog = bpf_patch_insn_data(env, adj_idx, patch, patch_len);
if (!new_prog)
return -ENOMEM;
env->prog = new_prog;
insns = new_prog->insnsi;
aux = env->insn_aux_data;
delta += 2;
delta += patch_len - 1;
}
return 0;
@ -8525,10 +8571,10 @@ skip_full_check:
/* do 32-bit optimization after insn patching has done so those patched
* insns could be handled correctly.
*/
if (ret == 0 && bpf_jit_needs_zext() &&
!bpf_prog_is_dev_bound(env->prog->aux)) {
ret = opt_subreg_zext_lo32(env);
env->prog->aux->verifier_zext = !ret;
if (ret == 0 && !bpf_prog_is_dev_bound(env->prog->aux)) {
ret = opt_subreg_zext_lo32_rnd_hi32(env, attr);
env->prog->aux->verifier_zext = bpf_jit_needs_zext() ? !ret
: false;
}
if (ret == 0)