Helpers and kfuncs independently tracked referenced object metadata using standalone id fields in 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 id and parent_id 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(). Add validate_ref_obj() to check for ambiguous ref_obj before using it. 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. Acked-by: Eduard Zingerman Signed-off-by: Amery Hung --- include/linux/bpf_verifier.h | 14 +- kernel/bpf/verifier.c | 122 +++++++++--------- .../bpf/progs/test_ringbuf_map_key.c | 11 +- tools/testing/selftests/bpf/verifier/calls.c | 24 ---- 4 files changed, 78 insertions(+), 93 deletions(-) diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 75b287d8d92f..b0521ba7787a 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -1424,6 +1424,18 @@ 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 parent_id; + u8 cnt; +}; + struct bpf_kfunc_call_arg_meta { /* In parameters */ struct btf *btf; @@ -1432,7 +1444,6 @@ struct bpf_kfunc_call_arg_meta { const struct btf_type *func_proto; const char *func_name; /* Out parameters */ - u32 id; u8 release_regno; bool r0_rdonly; u32 ret_btf_id; @@ -1470,6 +1481,7 @@ 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 3db0f1db475a..1a49e5194bb4 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -231,9 +231,28 @@ static void bpf_map_key_store(struct bpf_insn_aux_data *aux, u64 state) (poisoned ? BPF_MAP_KEY_POISON : 0ULL); } +static void update_ref_obj(struct ref_obj_desc *ref_obj, struct bpf_reg_state *reg) +{ + ref_obj->id = reg->id; + ref_obj->parent_id = reg->parent_id; + ref_obj->cnt++; +} + +static int validate_ref_obj(struct bpf_verifier_env *env, struct ref_obj_desc *ref_obj) +{ + if (ref_obj->cnt > 1) { + verifier_bug(env, "function expects only one referenced object but got %d\n", + ref_obj->cnt); + return -EFAULT; + } + + return 0; +} + 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; @@ -241,7 +260,6 @@ struct bpf_call_arg_meta { int access_size; int mem_size; u64 msize_max_value; - u32 id; int func_id; struct btf *btf; u32 btf_id; @@ -528,20 +546,6 @@ 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; @@ -670,11 +674,11 @@ 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; + int spi, i, err, parent_id = 0; enum bpf_dynptr_type type; spi = dynptr_get_spi(env, reg); @@ -707,6 +711,13 @@ static int mark_stack_slots_dynptr(struct bpf_verifier_env *env, struct bpf_reg_ return -EINVAL; if (dynptr->type == BPF_DYNPTR_TYPE_INVALID) { /* dynptr constructors */ + err = validate_ref_obj(env, ref_obj); + if (err) + return err; + + /* Track parent's id if the parent is a referenced object */ + parent_id = ref_obj->id; + if (dynptr_type_referenced(type)) { int id; @@ -7182,7 +7193,7 @@ 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; @@ -7223,7 +7234,7 @@ 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)) { @@ -7271,13 +7282,6 @@ static int process_dynptr_func(struct bpf_verifier_env *env, struct bpf_reg_stat return err; } -static u32 iter_ref_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.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); @@ -7310,6 +7314,7 @@ static bool is_kfunc_arg_iter(struct bpf_kfunc_call_arg_meta *meta, int arg_idx, 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_idx_from_argno(argno); int spi, err, i, nr_slots, btf_id; @@ -7381,7 +7386,7 @@ 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->id = iter_ref_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); @@ -8160,6 +8165,7 @@ 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; @@ -8226,15 +8232,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, meta->release_regno = regno; } - if (reg_is_referenced(env, reg) && base_type(arg_type) != ARG_KPTR_XCHG_DEST) { - if (meta->id) { - verbose(env, "more than one arg with referenced id R%d %u %u", - regno, reg->id, - meta->id); - return -EACCES; - } - meta->id = reg->id; - } + if (reg_is_referenced(env, reg)) + update_ref_obj(&meta->ref_obj, reg); switch (base_type(arg_type)) { case ARG_CONST_MAP_PTR: @@ -8373,7 +8372,7 @@ 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, &meta->ref_obj, &meta->dynptr); if (err) return err; @@ -9036,6 +9035,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog, struct bpf_subprog_info *sub = subprog_info(env, subprog); struct bpf_func_state *caller = cur_func(env); struct bpf_verifier_log *log = &env->log; + struct ref_obj_desc ref_obj = {}; u32 i; int ret, err; @@ -9113,7 +9113,7 @@ 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, &ref_obj, NULL); if (ret) return ret; } else if (base_type(arg->arg_type) == ARG_PTR_TO_BTF_ID) { @@ -10119,8 +10119,8 @@ 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.id) { - u32 id = meta.id; + } else if (func_id == BPF_FUNC_kptr_xchg && meta.ref_obj.id) { + u32 id = meta.ref_obj.id; bool in_rcu = in_rcu_cs(env); struct bpf_func_state *state; struct bpf_reg_state *reg; @@ -10139,10 +10139,10 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn } })); } - } else if (meta.id) { - err = release_reference(env, meta.id); + } else if (meta.ref_obj.id) { + err = release_reference(env, meta.ref_obj.id); } else if (bpf_register_is_null(®s[meta.release_regno])) { - /* meta.id can only be 0 if register that is meant to be + /* meta.ref_obj.id can only be 0 if register that is meant to be * released is NULL, which must be > R0. */ err = 0; @@ -10407,17 +10407,15 @@ 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) && - find_reference_state(env->cur_state, meta.id)) { + find_reference_state(env->cur_state, meta.ref_obj.id)) { struct bpf_verifier_state *branch; struct bpf_reg_state *r0; + err = validate_ref_obj(env, &meta.ref_obj); + if (err) + return err; + /* * In order for a release of any of the original or cast pointers * to invalidate all other pointers, reuse the same reference id for @@ -10435,7 +10433,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn r0->type = SCALAR_VALUE; regs[BPF_REG_0].type &= ~PTR_MAYBE_NULL; - regs[BPF_REG_0].id = meta.id; + regs[BPF_REG_0].id = meta.ref_obj.id; } else if (is_acquire_function(func_id, meta.map.ptr)) { int id = acquire_reference(env, insn_idx, 0); @@ -11909,13 +11907,13 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ } if (reg_is_referenced(env, reg)) { - if (is_kfunc_release(meta) && meta->id) { - verifier_bug(env, "more than one arg with referenced id %s %u %u", - reg_arg_name(env, argno), reg->id, - meta->id); + if (is_kfunc_release(meta) && meta->ref_obj.cnt) { + verbose(env, "more than one arg with referenced id %s %u %u", + reg_arg_name(env, argno), reg->id, + meta->ref_obj.id); return -EFAULT; } - meta->id = reg->id; + update_ref_obj(&meta->ref_obj, reg); if (is_kfunc_release(meta)) { if (regno < 0) { verbose(env, "%s release arg cannot be a stack argument\n", @@ -12098,7 +12096,7 @@ 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->id, &meta->dynptr); + &meta->ref_obj, &meta->dynptr); if (ret < 0) return ret; break; @@ -13042,8 +13040,12 @@ 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.id) - regs[BPF_REG_0].parent_id = meta.id; + if (meta.ref_obj.id) { + err = validate_ref_obj(env, &meta.ref_obj); + if (err) + return err; + regs[BPF_REG_0].parent_id = meta.ref_obj.id; + } if (is_kfunc_rcu_protected(&meta)) regs[BPF_REG_0].type |= MEM_RCU; diff --git a/tools/testing/selftests/bpf/progs/test_ringbuf_map_key.c b/tools/testing/selftests/bpf/progs/test_ringbuf_map_key.c index 21bb7da90ea5..0efafa927a3d 100644 --- a/tools/testing/selftests/bpf/progs/test_ringbuf_map_key.c +++ b/tools/testing/selftests/bpf/progs/test_ringbuf_map_key.c @@ -35,7 +35,7 @@ SEC("fentry/" SYS_PREFIX "sys_getpgid") int test_ringbuf_mem_map_key(void *ctx) { int cur_pid = bpf_get_current_pid_tgid() >> 32; - struct sample *sample, sample_copy; + struct sample *sample; int *lookup_val; if (cur_pid != pid) @@ -55,16 +55,11 @@ int test_ringbuf_mem_map_key(void *ctx) lookup_val = (int *)bpf_map_lookup_elem(&hash_map, sample); __sink(lookup_val); - /* workaround - memcpy is necessary so that verifier doesn't - * complain with: - * verifier internal error: more than one arg with ref_obj_id R3 - * when trying to do bpf_map_update_elem(&hash_map, sample, &sample->seq, BPF_ANY); - * + /* * Since bpf_map_lookup_elem above uses 'sample' as key, test using * sample field as value below */ - __builtin_memcpy(&sample_copy, sample, sizeof(struct sample)); - bpf_map_update_elem(&hash_map, &sample_copy, &sample->seq, BPF_ANY); + bpf_map_update_elem(&hash_map, sample, &sample->seq, BPF_ANY); bpf_ringbuf_submit(sample, 0); return 0; 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, -}, -- 2.53.0-Meta