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-rw-r--r--kernel/bpf/verifier.c36
1 files changed, 36 insertions, 0 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 04b2487..b414d6b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1729,6 +1729,13 @@ static int check_call(struct bpf_verifier_env *env, int func_id, int insn_idx)
err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta);
if (err)
return err;
+ if (func_id == BPF_FUNC_tail_call) {
+ if (meta.map_ptr == NULL) {
+ verbose(env, "verifier bug\n");
+ return -EINVAL;
+ }
+ env->insn_aux_data[insn_idx].map_ptr = meta.map_ptr;
+ }
err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta);
if (err)
return err;
@@ -4456,6 +4463,35 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
*/
insn->imm = 0;
insn->code = BPF_JMP | BPF_TAIL_CALL;
+
+ /* instead of changing every JIT dealing with tail_call
+ * emit two extra insns:
+ * if (index >= max_entries) goto out;
+ * index &= array->index_mask;
+ * to avoid out-of-bounds cpu speculation
+ */
+ map_ptr = env->insn_aux_data[i + delta].map_ptr;
+ if (map_ptr == BPF_MAP_PTR_POISON) {
+ verbose(env, "tail_call obusing map_ptr\n");
+ return -EINVAL;
+ }
+ if (!map_ptr->unpriv_array)
+ continue;
+ insn_buf[0] = BPF_JMP_IMM(BPF_JGE, BPF_REG_3,
+ map_ptr->max_entries, 2);
+ insn_buf[1] = BPF_ALU32_IMM(BPF_AND, BPF_REG_3,
+ container_of(map_ptr,
+ struct bpf_array,
+ map)->index_mask);
+ insn_buf[2] = *insn;
+ cnt = 3;
+ new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
+ if (!new_prog)
+ return -ENOMEM;
+
+ delta += cnt - 1;
+ env->prog = prog = new_prog;
+ insn = new_prog->insnsi + i + delta;
continue;
}
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