[PATCH v12 bpf-next 05/10] bpf: Refactor verifier dynptr into get_dynptr_arg_reg

Joanne Koong
2023-02-26T08:52:14Z

This commit refactors the logic for determining which register in a
function is the dynptr into "get_dynptr_arg_reg". This will be used
in the future when the dynptr reg for BPF_FUNC_dynptr_write will need
to be obtained in order to support writes for skb dynptrs.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
kernel/bpf/verifier.c | 80 +++++++++++++++++++++++++++----------------
1 file changed, 50 insertions(+), 30 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index a4cca21aefc3..cedd38292a62 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -6689,6 +6689,28 @@ int check_func_arg_reg_off(struct bpf_verifier_env *env,
}
}

+static struct bpf_reg_state *get_dynptr_arg_reg(struct bpf_verifier_env *env,
+ const struct bpf_func_proto *fn,
+ struct bpf_reg_state *regs)
+{
+ struct bpf_reg_state *state = NULL;
+ int i;
+
+ for (i = 0; i < MAX_BPF_FUNC_REG_ARGS; i++)
+ if (arg_type_is_dynptr(fn->arg_type[i])) {
+ if (state) {
+ verbose(env, "verifier internal error: multiple dynptr args\n");
+ return NULL;
+ }
+ state = &regs[BPF_REG_1 + i];
+ }
+
+ if (!state)
+ verbose(env, "verifier internal error: no dynptr arg found\n");
+
+ return state;
+}
+
static int dynptr_id(struct bpf_verifier_env *env, struct bpf_reg_state *reg)
{
struct bpf_func_state *state = func(env, reg);
@@ -8326,43 +8348,41 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
}
break;
case BPF_FUNC_dynptr_data:
- for (i = 0; i < MAX_BPF_FUNC_REG_ARGS; i++) {
- if (arg_type_is_dynptr(fn->arg_type[i])) {
- struct bpf_reg_state *reg = &regs[BPF_REG_1 + i];
- int id, ref_obj_id;
-
- if (meta.dynptr_id) {
- verbose(env, "verifier internal error: meta.dynptr_id already set\n");
- return -EFAULT;
- }
-
- if (meta.ref_obj_id) {
- verbose(env, "verifier internal error: meta.ref_obj_id already set\n");
- return -EFAULT;
- }
+ {
+ struct bpf_reg_state *reg;
+ int id, ref_obj_id;

- id = dynptr_id(env, reg);
- if (id < 0) {
- verbose(env, "verifier internal error: failed to obtain dynptr id\n");
- return id;
- }
+ reg = get_dynptr_arg_reg(env, fn, regs);
+ if (!reg)
+ return -EFAULT;

- ref_obj_id = dynptr_ref_obj_id(env, reg);
- if (ref_obj_id < 0) {
- verbose(env, "verifier internal error: failed to obtain dynptr ref_obj_id\n");
- return ref_obj_id;
- }

- meta.dynptr_id = id;
- meta.ref_obj_id = ref_obj_id;
- break;
- }
+ if (meta.dynptr_id) {
+ verbose(env, "verifier internal error: meta.dynptr_id already set\n");
+ return -EFAULT;
}
- if (i == MAX_BPF_FUNC_REG_ARGS) {
- verbose(env, "verifier internal error: no dynptr in bpf_dynptr_data()\n");
+ if (meta.ref_obj_id) {
+ verbose(env, "verifier internal error: meta.ref_obj_id already set\n");
return -EFAULT;
}
+
+ id = dynptr_id(env, reg);
+ if (id < 0) {
+ verbose(env, "verifier internal error: failed to obtain dynptr id\n");
+ return id;
+ }
+
+ ref_obj_id = dynptr_ref_obj_id(env, reg);
+ if (ref_obj_id < 0) {
+ verbose(env, "verifier internal error: failed to obtain dynptr ref_obj_id\n");
+ return ref_obj_id;
+ }
+
+ meta.dynptr_id = id;
+ meta.ref_obj_id = ref_obj_id;
+
break;
+ }
case BPF_FUNC_user_ringbuf_drain:
err = __check_func_call(env, insn, insn_idx_p, meta.subprogno,
set_user_ringbuf_callback_state);
--
2.34.1