Helpers and kfuncs independently tracked referenced object metadata (id, ref_obj_id) using separate fields on their respective arg_meta structs. This led to duplicated logic and inconsistent error handling between the two paths. Introduce struct ref_obj_desc to consolidate these fields along with a count of how many arguments carry a reference. Add update_ref_obj() to populate it from a bpf_reg_state, replacing open-coded assignments in check_func_arg(), check_kfunc_args(), and process_iter_arg(). Both helper and kfunc now use ref_obj.cnt to detect ambiguous ref_obj args. For ref_obj releasing helpers and kfuncs, keep checking it before calling update_ref_obj() for now. A later patch will make these functions not depending on ref_obj. For other users of ref_obj, move the checks to the use locations. For helper, this means moving the checks inside helper_multiple_ref_obj_use() to use locations. is_acquire_function() is dropped as ref_obj is never used. Pass ref_obj_desc into process_dynptr_func()/mark_stack_slots_dynptr() instead of a bare parent_id to make it less confusing. Drop the selftest introduced in 7ec899ac90a2 (“selftests/bpf: Negative test case for ref_obj_id in args”) since the verifier no longer complains about ambiguous ref_obj if it is not used. Signed-off-by: Amery Hung --- include/linux/bpf_verifier.h | 15 ++- kernel/bpf/verifier.c | 111 +++++++++---------- tools/testing/selftests/bpf/verifier/calls.c | 24 ---- 3 files changed, 68 insertions(+), 82 deletions(-) diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 51d5f5dd6e5b..a531be98fedf 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -1397,6 +1397,18 @@ struct bpf_dynptr_desc { u32 parent_id; }; +/* + * The last seen rereferenced object; Updated by update_ref_obj() when a register refers to a + * referenced object. Used when the helper or kfunc is releasing a referenced object, casting + * a referenced object, returning allocated memory derived from referenced object or creating + * a dynptr with a referenced object as parent. + */ +struct ref_obj_desc { + u32 id; + u32 ref_obj_id; + u8 cnt; +}; + struct bpf_kfunc_call_arg_meta { /* In parameters */ struct btf *btf; @@ -1405,8 +1417,6 @@ struct bpf_kfunc_call_arg_meta { const struct btf_type *func_proto; const char *func_name; /* Out parameters */ - u32 ref_obj_id; - u32 id; u8 release_regno; bool r0_rdonly; u32 ret_btf_id; @@ -1444,6 +1454,7 @@ struct bpf_kfunc_call_arg_meta { } iter; struct bpf_map_desc map; struct bpf_dynptr_desc dynptr; + struct ref_obj_desc ref_obj; u64 mem_size; }; diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 792e61e07b06..542912c7983f 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -234,6 +234,7 @@ static void bpf_map_key_store(struct bpf_insn_aux_data *aux, u64 state) struct bpf_call_arg_meta { struct bpf_map_desc map; struct bpf_dynptr_desc dynptr; + struct ref_obj_desc ref_obj; bool raw_mode; bool pkt_access; u8 release_regno; @@ -525,20 +526,6 @@ bool bpf_is_may_goto_insn(struct bpf_insn *insn) return insn->code == (BPF_JMP | BPF_JCOND) && insn->src_reg == BPF_MAY_GOTO; } -static bool helper_multiple_ref_obj_use(enum bpf_func_id func_id, - const struct bpf_map *map) -{ - int ref_obj_uses = 0; - - if (is_ptr_cast_function(func_id)) - ref_obj_uses++; - if (is_acquire_function(func_id, map)) - ref_obj_uses++; - - return ref_obj_uses > 1; -} - - static bool is_spi_bounds_valid(struct bpf_func_state *state, int spi, int nr_slots) { int allocated_slots = state->allocated_stack / BPF_REG_SIZE; @@ -667,11 +654,11 @@ static int destroy_if_dynptr_stack_slot(struct bpf_verifier_env *env, struct bpf_func_state *state, int spi); static int mark_stack_slots_dynptr(struct bpf_verifier_env *env, struct bpf_reg_state *reg, - enum bpf_arg_type arg_type, int insn_idx, int parent_id, - struct bpf_dynptr_desc *dynptr) + enum bpf_arg_type arg_type, int insn_idx, + struct ref_obj_desc *ref_obj, struct bpf_dynptr_desc *dynptr) { struct bpf_func_state *state = bpf_func(env, reg); - int spi, i, err, ref_obj_id = 0; + int spi, i, err, ref_obj_id = 0, parent_id = 0; enum bpf_dynptr_type type; spi = dynptr_get_spi(env, reg); @@ -713,6 +700,13 @@ static int mark_stack_slots_dynptr(struct bpf_verifier_env *env, struct bpf_reg_ return ref_obj_id; } /* Track parent's id if the parent is a referenced object */ + if (ref_obj && ref_obj->ref_obj_id) { + if (ref_obj->cnt > 1) { + verifier_bug(env, "function expects only one referenced object but got %d\n", ref_obj->cnt); + return -EFAULT; + } + parent_id = ref_obj->id; + } } else { /* bpf_dynptr_clone() */ ref_obj_id = dynptr->ref_obj_id; parent_id = dynptr->parent_id; @@ -6982,7 +6976,7 @@ static int process_kptr_func(struct bpf_verifier_env *env, int regno, */ static int process_dynptr_func(struct bpf_verifier_env *env, struct bpf_reg_state *reg, argno_t argno, int insn_idx, enum bpf_arg_type arg_type, - int parent_id, struct bpf_dynptr_desc *dynptr) + struct ref_obj_desc *ref_obj, struct bpf_dynptr_desc *dynptr) { int spi, err = 0; @@ -7023,7 +7017,7 @@ static int process_dynptr_func(struct bpf_verifier_env *env, struct bpf_reg_stat return err; } - err = mark_stack_slots_dynptr(env, reg, arg_type, insn_idx, parent_id, dynptr); + err = mark_stack_slots_dynptr(env, reg, arg_type, insn_idx, ref_obj, dynptr); } else /* OBJ_RELEASE and None case from above */ { /* For the reg->type == PTR_TO_STACK case, bpf_dynptr is never const */ if (reg->type == CONST_PTR_TO_DYNPTR && (arg_type & OBJ_RELEASE)) { @@ -7072,13 +7066,6 @@ static int process_dynptr_func(struct bpf_verifier_env *env, struct bpf_reg_stat return err; } -static u32 iter_ref_obj_id(struct bpf_verifier_env *env, struct bpf_reg_state *reg, int spi) -{ - struct bpf_func_state *state = bpf_func(env, reg); - - return state->stack[spi].spilled_ptr.ref_obj_id; -} - static bool is_iter_kfunc(struct bpf_kfunc_call_arg_meta *meta) { return meta->kfunc_flags & (KF_ITER_NEW | KF_ITER_NEXT | KF_ITER_DESTROY); @@ -7108,9 +7095,17 @@ static bool is_kfunc_arg_iter(struct bpf_kfunc_call_arg_meta *meta, int arg_idx, return btf_param_match_suffix(meta->btf, arg, "__iter"); } +static void update_ref_obj(struct ref_obj_desc *ref_obj, struct bpf_reg_state *reg) +{ + ref_obj->id = reg->id; + ref_obj->ref_obj_id = reg->ref_obj_id; + ref_obj->cnt++; +} + static int process_iter_arg(struct bpf_verifier_env *env, struct bpf_reg_state *reg, argno_t argno, int insn_idx, struct bpf_kfunc_call_arg_meta *meta) { + struct bpf_func_state *state = bpf_func(env, reg); const struct btf_type *t; u32 arg_idx = arg_from_argno(argno) - 1; int spi, err, i, nr_slots, btf_id; @@ -7182,7 +7177,7 @@ static int process_iter_arg(struct bpf_verifier_env *env, struct bpf_reg_state * /* remember meta->iter info for process_iter_next_call() */ meta->iter.spi = spi; meta->iter.frameno = reg->frameno; - meta->ref_obj_id = iter_ref_obj_id(env, reg, spi); + update_ref_obj(&meta->ref_obj, &state->stack[spi].spilled_ptr); if (is_iter_destroy_kfunc(meta)) { err = unmark_stack_slots_iter(env, reg, nr_slots); @@ -7961,6 +7956,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, u32 regno = BPF_REG_1 + arg; struct bpf_reg_state *reg = reg_state(env, regno); enum bpf_arg_type arg_type = fn->arg_type[arg]; + argno_t argno = argno_from_arg(arg + 1); enum bpf_reg_type type = reg->type; u32 *arg_btf_id = NULL; u32 key_size; @@ -8028,14 +8024,13 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, } if (reg->ref_obj_id && base_type(arg_type) != ARG_KPTR_XCHG_DEST) { - if (meta->ref_obj_id) { - verbose(env, "more than one arg with ref_obj_id R%d %u %u", - regno, reg->ref_obj_id, - meta->ref_obj_id); + if (meta->release_regno && meta->ref_obj.cnt) { + verbose(env, "more than one arg with ref_obj_id %s %u %u", + reg_arg_name(env, argno), reg->ref_obj_id, + meta->ref_obj.ref_obj_id); return -EACCES; } - meta->ref_obj_id = reg->ref_obj_id; - meta->id = reg->id; + update_ref_obj(&meta->ref_obj, reg); } switch (base_type(arg_type)) { @@ -8175,7 +8170,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, true, meta); break; case ARG_PTR_TO_DYNPTR: - err = process_dynptr_func(env, reg, argno_from_reg(regno), insn_idx, arg_type, 0, + err = process_dynptr_func(env, reg, argno_from_reg(regno), insn_idx, arg_type, NULL, &meta->dynptr); if (err) return err; @@ -8900,7 +8895,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog, if (ret) return ret; - ret = process_dynptr_func(env, reg, argno, -1, arg->arg_type, 0, NULL); + ret = process_dynptr_func(env, reg, argno, -1, arg->arg_type, NULL, NULL); if (ret) return ret; } else if (base_type(arg->arg_type) == ARG_PTR_TO_BTF_ID) { @@ -9878,8 +9873,8 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn err = -EINVAL; if (arg_type_is_dynptr(fn->arg_type[meta.release_regno - BPF_REG_1])) { err = unmark_stack_slots_dynptr(env, ®s[meta.release_regno]); - } else if (func_id == BPF_FUNC_kptr_xchg && meta.ref_obj_id) { - u32 ref_obj_id = meta.ref_obj_id; + } else if (func_id == BPF_FUNC_kptr_xchg && meta.ref_obj.ref_obj_id) { + u32 ref_obj_id = meta.ref_obj.ref_obj_id; bool in_rcu = in_rcu_cs(env); struct bpf_func_state *state; struct bpf_reg_state *reg; @@ -9898,10 +9893,10 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn } })); } - } else if (meta.ref_obj_id) { - err = release_reference(env, meta.ref_obj_id); + } else if (meta.ref_obj.ref_obj_id) { + err = release_reference(env, meta.ref_obj.ref_obj_id); } else if (bpf_register_is_null(®s[meta.release_regno])) { - /* meta.ref_obj_id can only be 0 if register that is meant to be + /* meta.ref_obj.ref_obj_id can only be 0 if register that is meant to be * released is NULL, which must be > R0. */ err = 0; @@ -10165,15 +10160,14 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn if (type_may_be_null(regs[BPF_REG_0].type)) regs[BPF_REG_0].id = ++env->id_gen; - if (helper_multiple_ref_obj_use(func_id, meta.map.ptr)) { - verifier_bug(env, "func %s#%d sets ref_obj_id more than once", - func_id_name(func_id), func_id); - return -EFAULT; - } - if (is_ptr_cast_function(func_id)) { /* For release_reference() */ - regs[BPF_REG_0].ref_obj_id = meta.ref_obj_id; + if (meta.ref_obj.cnt > 1) { + verifier_bug(env, "function expects only one referenced object but got %d\n", + meta.ref_obj.cnt); + return -EFAULT; + } + regs[BPF_REG_0].ref_obj_id = meta.ref_obj.ref_obj_id; } else if (is_acquire_function(func_id, meta.map.ptr)) { int id = acquire_reference(env, insn_idx); @@ -11616,14 +11610,13 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ } if (reg->ref_obj_id) { - if (is_kfunc_release(meta) && meta->ref_obj_id) { - verifier_bug(env, "more than one arg with ref_obj_id %s %u %u", - reg_arg_name(env, argno), reg->ref_obj_id, - meta->ref_obj_id); + if (is_kfunc_release(meta) && meta->ref_obj.cnt) { + verbose(env, "more than one arg with ref_obj_id %s %u %u", + reg_arg_name(env, argno), reg->ref_obj_id, + meta->ref_obj.ref_obj_id); return -EFAULT; } - meta->ref_obj_id = reg->ref_obj_id; - meta->id = reg->id; + update_ref_obj(&meta->ref_obj, reg); if (is_kfunc_release(meta)) meta->release_regno = regno; } @@ -11794,7 +11787,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ } ret = process_dynptr_func(env, reg, argno, insn_idx, dynptr_arg_type, - meta->ref_obj_id ? meta->id : 0, &meta->dynptr); + &meta->ref_obj, &meta->dynptr); if (ret < 0) return ret; break; @@ -12740,8 +12733,14 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, regs[BPF_REG_0].type |= MEM_RDONLY; /* Ensures we don't access the memory after a release_reference() */ - if (meta.ref_obj_id) - regs[BPF_REG_0].parent_id = meta.ref_obj_id; + if (meta.ref_obj.ref_obj_id) { + if (meta.ref_obj.cnt > 1) { + verifier_bug(env, "function expects only one referenced object but got %d\n", + meta.ref_obj.cnt); + return -EFAULT; + } + regs[BPF_REG_0].parent_id = meta.ref_obj.ref_obj_id; + } if (is_kfunc_rcu_protected(&meta)) regs[BPF_REG_0].type |= MEM_RCU; diff --git a/tools/testing/selftests/bpf/verifier/calls.c b/tools/testing/selftests/bpf/verifier/calls.c index 0bb4337552c8..42d523a21a43 100644 --- a/tools/testing/selftests/bpf/verifier/calls.c +++ b/tools/testing/selftests/bpf/verifier/calls.c @@ -2410,27 +2410,3 @@ .errstr_unpriv = "", .prog_type = BPF_PROG_TYPE_CGROUP_SKB, }, -{ - "calls: several args with ref_obj_id", - .insns = { - /* Reserve at least sizeof(struct iphdr) bytes in the ring buffer. - * With a smaller size, the verifier would reject the call to - * bpf_tcp_raw_gen_syncookie_ipv4 before we can reach the - * ref_obj_id error. - */ - BPF_MOV64_IMM(BPF_REG_2, 20), - BPF_MOV64_IMM(BPF_REG_3, 0), - BPF_LD_MAP_FD(BPF_REG_1, 0), - BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_reserve), - /* if r0 == 0 goto */ - BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 3), - BPF_MOV64_REG(BPF_REG_1, BPF_REG_0), - BPF_MOV64_REG(BPF_REG_2, BPF_REG_0), - BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_tcp_raw_gen_syncookie_ipv4), - BPF_EXIT_INSN(), - }, - .fixup_map_ringbuf = { 2 }, - .result = REJECT, - .errstr = "more than one arg with ref_obj_id", - .prog_type = BPF_PROG_TYPE_SCHED_CLS, -}, -- 2.52.0