From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-176.mta1.migadu.com (out-176.mta1.migadu.com [95.215.58.176]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BC91950257 for ; Thu, 8 Feb 2024 23:01:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.176 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707433309; cv=none; b=Ctv6geeAWdF+GXGo7OZT8PEMwojuF4IIFXeP8fZ4X83Wu5SqioyqetGXDN5uWzF73YYYuteu4WxqDPc28q2oBqIUvIueLndEEct6gcSK2I1Ii7ACK80qWgB9jO926M5B0mcufUELaRyv+UeaZ9jk+R89SO0UzPUbffERjOqf46w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707433309; c=relaxed/simple; bh=JY73RQYGLHFfADFaNHRGwO5l42hBhjzfxAd6Ifzb7JE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=cGmYmK+u7qgWj7rT9BiyvwxCEHcf9h5rrQErabWniwRbUOqNM9sc1VJQmPSYM5JktEY980rbAXVxGhqa7C357/8b56m7gxRlw8264eeOVMRkXqRhR2Ycxp8p2LZLOyhby1vhBbSObWuOQ2ze+RiYnatNl6VkGSCchWRj6e+WMnU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=nyh1ZMIb; arc=none smtp.client-ip=95.215.58.176 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="nyh1ZMIb" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1707433304; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=OQ4075DJBtI5zjjQrGVC8aJPKhnn6A816766ml/kCOs=; b=nyh1ZMIbaafZf/LCldh4uGPTbePnZ0IGgw/ZhWyY3CRBiRngTMf/FYlsuvkSUs2E4HOEKa AtSmfTo8s2lfQzW1kH4RP+eFJ9M2TR5HNmJm4JxbeX04QHDy7FLjgRVTD74aq/9H0GmfPG hejaYJc3ssQyOmlAdfNhAVdjG61Ipe4= Date: Thu, 8 Feb 2024 15:01:34 -0800 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf-next v6 3/4] bpf: Create argument information for nullable arguments. Content-Language: en-US To: thinker.li@gmail.com Cc: sinquersw@gmail.com, kuifeng@meta.com, bpf@vger.kernel.org, ast@kernel.org, song@kernel.org, kernel-team@meta.com, andrii@kernel.org, davemarchevsky@meta.com, dvernet@meta.com References: <20240208065103.2154768-1-thinker.li@gmail.com> <20240208065103.2154768-4-thinker.li@gmail.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Martin KaFai Lau In-Reply-To: <20240208065103.2154768-4-thinker.li@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 2/7/24 10:51 PM, thinker.li@gmail.com wrote: > From: Kui-Feng Lee > > Collect argument information from the type information of stub functions to > mark arguments of BPF struct_ops programs with PTR_MAYBE_NULL if they are > nullable. A nullable argument is annotated by suffixing "__nullable" at > the argument name of stub function. > > For nullable arguments, this patch sets an arg_info to label their reg_type > with PTR_TO_BTF_ID | PTR_TRUSTED | PTR_MAYBE_NULL. This makes the verifier > to check programs and ensure that they properly check the pointer. The > programs should check if the pointer is null before accessing the pointed > memory. > > The implementer of a struct_ops type should annotate the arguments that can > be null. The implementer should define a stub function (empty) as a > placeholder for each defined operator. The name of a stub function should > be in the pattern "__". For example, for > test_maybe_null of struct bpf_testmod_ops, it's stub function name should > be "bpf_testmod_ops__test_maybe_null". You mark an argument nullable by > suffixing the argument name with "__nullable" at the stub function. > > Since we already has stub functions for kCFI, we just reuse these stub > functions with the naming convention mentioned earlier. These stub > functions with the naming convention is only required if there are nullable > arguments to annotate. For functions having not nullable arguments, stub > functions are not necessary for the purpose of this patch. > > This patch will prepare a list of struct bpf_ctx_arg_aux, aka arg_info, for > each member field of a struct_ops type. "arg_info" will be assigned to > "prog->aux->ctx_arg_info" of BPF struct_ops programs in > check_struct_ops_btf_id() so that it can be used by btf_ctx_access() later > to set reg_type properly for the verifier. One more nit on the naming. It is my overlook in v5. There are also things that need to address in btf_ctx_arg_offset(). Comment inlined below. Other patches of the set lgtm. > > Signed-off-by: Kui-Feng Lee > --- > include/linux/bpf.h | 22 ++++ > include/linux/btf.h | 2 + > kernel/bpf/bpf_struct_ops.c | 197 ++++++++++++++++++++++++++++++++++-- > kernel/bpf/btf.c | 33 ++++++ > kernel/bpf/verifier.c | 6 ++ > 5 files changed, 253 insertions(+), 7 deletions(-) > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > index 9a2ee9456989..6908bd2360ea 100644 > --- a/include/linux/bpf.h > +++ b/include/linux/bpf.h > @@ -1709,6 +1709,19 @@ struct bpf_struct_ops { > struct btf_func_model func_models[BPF_STRUCT_OPS_MAX_NR_MEMBERS]; > }; > > +/* Every member of a struct_ops type has an instance even a member is not > + * an operator (function pointer). The "arg_info" field will be assigned to > + * prog->aux->ctx_arg_info of BPF struct_ops programs to provide the > + * argument information required by the verifier to verify the program. > + * > + * btf_ctx_access() will lookup prog->aux->ctx_arg_info to find the > + * corresponding entry for an given argument. > + */ > +struct bpf_struct_ops_arg_info { > + struct bpf_ctx_arg_aux *arg_info; One more nit on naming, It is my overlook in v5. After looking at how "arg_info" means both "bpf_struct_ops_arg_info" and "bpf_ctx_arg_aux" in this patch, could you do one more rename here and shorten the "*arg_info" here to "*info". > + u32 arg_info_cnt; and "info_cnt" or just "cnt" here. > +}; > + > struct bpf_struct_ops_desc { > struct bpf_struct_ops *st_ops; > > @@ -1716,6 +1729,9 @@ struct bpf_struct_ops_desc { > const struct btf_type *value_type; > u32 type_id; > u32 value_id; > + > + /* Collection of argument information for each member */ > + struct bpf_struct_ops_arg_info *arg_info; > }; > > enum bpf_struct_ops_state { > @@ -1790,6 +1806,8 @@ int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc, > struct btf *btf, > struct bpf_verifier_log *log); > void bpf_map_struct_ops_info_fill(struct bpf_map_info *info, struct bpf_map *map); > +void bpf_struct_ops_desc_release(struct bpf_struct_ops_desc *st_ops_desc, > + int len); > #else > #define register_bpf_struct_ops(st_ops, type) ({ (void *)(st_ops); 0; }) > static inline bool bpf_try_module_get(const void *data, struct module *owner) > @@ -1814,6 +1832,10 @@ static inline void bpf_map_struct_ops_info_fill(struct bpf_map_info *info, struc > { > } > > +static inline void bpf_struct_ops_desc_release(struct bpf_struct_ops_desc *st_ops_desc, int len) > +{ > +} > + > #endif > > #if defined(CONFIG_CGROUP_BPF) && defined(CONFIG_BPF_LSM) > diff --git a/include/linux/btf.h b/include/linux/btf.h > index df76a14c64f6..15ee845e6b38 100644 > --- a/include/linux/btf.h > +++ b/include/linux/btf.h > @@ -498,6 +498,8 @@ static inline void *btf_id_set8_contains(const struct btf_id_set8 *set, u32 id) > bool btf_param_match_suffix(const struct btf *btf, > const struct btf_param *arg, > const char *suffix); > +int btf_ctx_arg_offset(struct btf *btf, const struct btf_type *func_proto, > + u32 arg_no); > > struct bpf_verifier_log; > > diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c > index f98f580de77a..e9cc8c847736 100644 > --- a/kernel/bpf/bpf_struct_ops.c > +++ b/kernel/bpf/bpf_struct_ops.c > @@ -116,17 +116,177 @@ static bool is_valid_value_type(struct btf *btf, s32 value_id, > return true; > } > > +#define MAYBE_NULL_SUFFIX "__nullable" > +#define MAX_STUB_NAME 128 > + > +/* Return the type info of a stub function, if it exists. > + * > + * The name of a stub function is made up of the name of the struct_ops and > + * the name of the function pointer member, separated by "__". For example, > + * if the struct_ops type is named "foo_ops" and the function pointer > + * member is named "bar", the stub function name would be "foo_ops__bar". > + */ > +static const struct btf_type * > +find_stub_func_proto(struct btf *btf, const char *st_op_name, > + const char *member_name) > +{ > + char stub_func_name[MAX_STUB_NAME]; > + const struct btf_type *func_type; > + s32 btf_id; > + int cp; > + > + cp = snprintf(stub_func_name, MAX_STUB_NAME, "%s__%s", > + st_op_name, member_name); > + if (cp >= MAX_STUB_NAME) { > + pr_warn("Stub function name too long\n"); > + return NULL; > + } > + btf_id = btf_find_by_name_kind(btf, stub_func_name, BTF_KIND_FUNC); > + if (btf_id < 0) > + return NULL; > + func_type = btf_type_by_id(btf, btf_id); > + if (!func_type) > + return NULL; > + > + return btf_type_by_id(btf, func_type->type); /* FUNC_PROTO */ > +} > + > +/* Prepare argument info for every nullable argument of a member of a > + * struct_ops type. > + * > + * Initialize a struct bpf_struct_ops_arg_info according to type info of > + * the arguments of a stub function. (Check kCFI for more information about > + * stub functions.) > + * > + * Each member in the struct_ops type has a struct bpf_struct_ops_arg_info > + * to provide an array of struct bpf_ctx_arg_aux, which in turn provides > + * the information that used by the verifier to check the arguments of the > + * BPF struct_ops program assigned to the member. Here, we only care about > + * the arguments that are marked as __nullable. > + * > + * The array of struct bpf_ctx_arg_aux is eventually assigned to > + * prog->aux->ctx_arg_info of BPF struct_ops programs and passed to the > + * verifier. (See check_struct_ops_btf_id()) > + * > + * all_arg_info->arg_info will be the list of struct bpf_ctx_arg_aux if > + * success. If fails, it will be kept untouched. > + */ > +static int prepare_arg_info(struct btf *btf, > + const char *st_ops_name, > + const char *member_name, > + const struct btf_type *func_proto, > + struct bpf_struct_ops_arg_info *all_arg_info) s/all_arg_info/arg_info/ > +{ > + const struct btf_type *stub_func_proto, *pointed_type; > + struct bpf_ctx_arg_aux *arg_info, *arg_info_buf; s/arg_info/info/ s/arg_info_buf/info_buf/ > + const struct btf_param *stub_args, *args; > + u32 nargs, arg_no, arg_info_cnt = 0; > + s32 arg_btf_id; > + int offset; > + > + stub_func_proto = find_stub_func_proto(btf, st_ops_name, member_name); > + if (!stub_func_proto) > + return 0; > + > + /* Check if the number of arguments of the stub function is the same > + * as the number of arguments of the function pointer. > + */ > + nargs = btf_type_vlen(func_proto); > + if (nargs != btf_type_vlen(stub_func_proto)) { > + pr_warn("the number of arguments of the stub function %s__%s does not match the number of arguments of the member %s of struct %s\n", > + st_ops_name, member_name, member_name, st_ops_name); > + return -EINVAL; > + } > + > + args = btf_params(func_proto); > + stub_args = btf_params(stub_func_proto); > + > + arg_info_buf = kcalloc(nargs, sizeof(*arg_info_buf), GFP_KERNEL); > + if (!arg_info_buf) > + return -ENOMEM; > + > + /* Prepare arg_info for every nullable argument */ > + arg_info = arg_info_buf; > + for (arg_no = 0; arg_no < nargs; arg_no++) { > + /* Skip arguments that is not suffixed with > + * "__nullable". > + */ > + if (!btf_param_match_suffix(btf, &stub_args[arg_no], > + MAYBE_NULL_SUFFIX)) > + continue; > + > + /* Should be a pointer to struct */ > + pointed_type = btf_type_resolve_ptr(btf, > + args[arg_no].type, > + &arg_btf_id); > + if (!pointed_type || > + !btf_type_is_struct(pointed_type)) pr_warn("stub function %s__%s has %s tagging to an unsupported type\n", st_ops_name, member_name, MAYBE_NULL_SUFFIX); > + goto err_out; > + > + offset = btf_ctx_arg_offset(btf, func_proto, arg_no); > + if (offset < 0) pr_warn("stub function %s__%s has invalid trampoline ctx offset for arg#%u\n", st_ops_name, member_name, arg_no); > + goto err_out; > + > + /* Fill the information of the new argument */ > + arg_info->reg_type = > + PTR_TRUSTED | PTR_TO_BTF_ID | PTR_MAYBE_NULL; > + arg_info->btf_id = arg_btf_id; > + arg_info->btf = btf; > + arg_info->offset = offset; > + > + arg_info++; > + arg_info_cnt++; > + } > + > + if (arg_info_cnt) { > + all_arg_info->arg_info = arg_info_buf; > + all_arg_info->arg_info_cnt = arg_info_cnt; > + } else { > + kfree(arg_info_buf); > + } > + > + return 0; > + > +err_out: > + kfree(arg_info_buf); > + > + return -EINVAL; > +} > + > +/* Clean up the arg_info in a struct bpf_struct_ops_desc. > + * > + * The callers should pass the length of st_ops_desc->arg_info. The length > + * can not be derived from std_ops_desc->type since the list may be > + * incomplete. > + */ > +void bpf_struct_ops_desc_release(struct bpf_struct_ops_desc *st_ops_desc, > + int len) The "len" argument is not needed. It is the btf_type_vlen(st_ops_desc->type). Initialize the st_ops_desc->type/value_type/type_id/value_id earlier if necessary. > +{ > + struct bpf_struct_ops_arg_info *arg_info; > + int i; > + > + arg_info = st_ops_desc->arg_info; > + if (!arg_info) > + return; > + > + for (i = 0; i < len; i++) > + kfree(arg_info[i].arg_info); > + > + kfree(arg_info); > +} > + > int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc, > struct btf *btf, > struct bpf_verifier_log *log) > { > struct bpf_struct_ops *st_ops = st_ops_desc->st_ops; > + struct bpf_struct_ops_arg_info *arg_info; > const struct btf_member *member; > const struct btf_type *t; > s32 type_id, value_id; > char value_name[128]; > const char *mname; > - int i; > + int i, err; > > if (strlen(st_ops->name) + VALUE_PREFIX_LEN >= > sizeof(value_name)) { > @@ -160,6 +320,12 @@ int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc, > if (!is_valid_value_type(btf, value_id, t, value_name)) > return -EINVAL; > > + arg_info = kcalloc(btf_type_vlen(t), sizeof(*arg_info), > + GFP_KERNEL); > + if (!arg_info) > + return -ENOMEM; > + > + st_ops_desc->arg_info = arg_info; > for_each_member(i, t, member) { > const struct btf_type *func_proto; > > @@ -167,32 +333,44 @@ int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc, > if (!*mname) { > pr_warn("anon member in struct %s is not supported\n", > st_ops->name); > - return -EOPNOTSUPP; > + err = -EOPNOTSUPP; > + goto errout; > } > > if (__btf_member_bitfield_size(t, member)) { > pr_warn("bit field member %s in struct %s is not supported\n", > mname, st_ops->name); > - return -EOPNOTSUPP; > + err = -EOPNOTSUPP; > + goto errout; > } > > func_proto = btf_type_resolve_func_ptr(btf, > member->type, > NULL); > - if (func_proto && > - btf_distill_func_proto(log, btf, > + if (!func_proto) > + continue; > + > + if (btf_distill_func_proto(log, btf, > func_proto, mname, > &st_ops->func_models[i])) { > pr_warn("Error in parsing func ptr %s in struct %s\n", > mname, st_ops->name); > - return -EINVAL; > + err = -EINVAL; > + goto errout; > } > + > + err = prepare_arg_info(btf, st_ops->name, mname, > + func_proto, > + arg_info + i); > + if (err) > + goto errout; > } > > if (st_ops->init(btf)) { > pr_warn("Error in init bpf_struct_ops %s\n", > st_ops->name); > - return -EINVAL; > + err = -EINVAL; > + goto errout; > } > > st_ops_desc->type_id = type_id; > @@ -201,6 +379,11 @@ int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc, > st_ops_desc->value_type = btf_type_by_id(btf, value_id); > > return 0; > + > +errout: > + bpf_struct_ops_desc_release(st_ops_desc, i); > + > + return err; > } > > static int bpf_struct_ops_map_get_next_key(struct bpf_map *map, void *key, > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c > index e3508b8008a2..554a57a0eaa5 100644 > --- a/kernel/bpf/btf.c > +++ b/kernel/bpf/btf.c > @@ -1699,6 +1699,14 @@ static void btf_free_struct_meta_tab(struct btf *btf) > static void btf_free_struct_ops_tab(struct btf *btf) > { > struct btf_struct_ops_tab *tab = btf->struct_ops_tab; > + int i; > + > + if (!tab) > + return; > + > + for (i = 0; i < tab->cnt; i++) > + bpf_struct_ops_desc_release(&tab->ops[i], > + btf_type_vlen(tab->ops[i].type)); > > kfree(tab); > btf->struct_ops_tab = NULL; > @@ -6130,6 +6138,31 @@ static bool prog_args_trusted(const struct bpf_prog *prog) > } > } > > +int btf_ctx_arg_offset(struct btf *btf, const struct btf_type *func_proto, > + u32 arg_no) > +{ > + const struct btf_param *args; > + const struct btf_type *t; > + int off = 0, i; > + u32 sz, nargs; > + > + nargs = btf_type_vlen(func_proto); > + /* It is the return value if arg_no == nargs */ I forgot to mention this in v5. This comment is not accurate. This function is trying to figure out the trampoline ctx offset for a particular arg_no. arg_no cannot be the return value and arg_no cannot be >= nargs. > + if (arg_no > nargs) so remove this check all together. > + return -EINVAL; > + > + args = btf_params(func_proto); > + for (i = 0; i < arg_no; i++) { > + t = btf_type_by_id(btf, args[i].type); > + t = btf_resolve_size(btf, t, &sz); > + if (IS_ERR(t)) > + return -EINVAL; return PTR_ERR(t); > + off += roundup(sz, 8); > + } > + > + return off; > +} > + > bool btf_ctx_access(int off, int size, enum bpf_access_type type, > const struct bpf_prog *prog, > struct bpf_insn_access_aux *info) > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index 7edd70eec7dd..7826d6e6a09b 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -20415,6 +20415,12 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env) > } > } > > + /* btf_ctx_access() used this to provide argument type info */ > + prog->aux->ctx_arg_info = > + st_ops_desc->arg_info[member_idx].arg_info; > + prog->aux->ctx_arg_info_size = > + st_ops_desc->arg_info[member_idx].arg_info_cnt; > + > prog->aux->attach_func_proto = func_proto; > prog->aux->attach_func_name = mname; > env->ops = st_ops->verifier_ops;