| Message ID | 20240206063833.2520479-3-thinker.li@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | Support PTR_MAYBE_NULL for struct_ops arguments. | expand |
On 2/5/24 10:38 PM, thinker.li@gmail.com wrote: > From: Kui-Feng Lee <thinker.li@gmail.com> > > 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 "<st_op_type>__<operator name>". 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. > > Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com> > --- > include/linux/bpf.h | 18 ++++ > kernel/bpf/bpf_struct_ops.c | 185 ++++++++++++++++++++++++++++++++++-- > kernel/bpf/btf.c | 40 ++++++++ > kernel/bpf/verifier.c | 6 ++ > 4 files changed, 242 insertions(+), 7 deletions(-) > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > index 9a2ee9456989..29d9ec1c4fd9 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 the member is not > + * an operator (function pointer). The "arg_info" field will be assigned to > + * prog->aux->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->arg_info to find the > + * corresponding entry for an given argument. > + */ > +struct bpf_struct_ops_member_arg_info { nit. Shorten it to bpf_struct_ops_arg_info. > + struct bpf_ctx_arg_aux *arg_info; > + u32 arg_info_cnt; > +}; > + > 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_member_arg_info *member_arg_info; nit. Same here on the struct's field name. s/member_arg_info/arg_info(s)/. > }; > > enum bpf_struct_ops_state { > @@ -2500,6 +2516,8 @@ int bpf_prog_test_run_sk_lookup(struct bpf_prog *prog, > int bpf_prog_test_run_nf(struct bpf_prog *prog, > const union bpf_attr *kattr, > union bpf_attr __user *uattr); > +int btf_ctx_arg_offset(struct btf *btf, const struct btf_type *func_proto, > + u32 arg_no); This should be in btf.h. Its implementation is also in btf.c in this patch. > 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/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c > index f98f580de77a..0db7e12a9244 100644 > --- a/kernel/bpf/bpf_struct_ops.c > +++ b/kernel/bpf/bpf_struct_ops.c > @@ -116,17 +116,162 @@ static bool is_valid_value_type(struct btf *btf, s32 value_id, > return true; > } > > +#define MAYBE_NULL_SUFFIX "__nullable" > +#define MAX_STUB_NAME 128 > + > +static bool match_nullable_suffix(const char *name) > +{ > + int suffix_len, len; > + > + if (!name) > + return false; > + > + suffix_len = sizeof(MAYBE_NULL_SUFFIX) - 1; > + len = strlen(name); > + if (len <= suffix_len) This function looks almost the same as __kfunc_param_match_suffix. How about refactor __kfunc_param_match_suffix (to btf.c?) and resue here to avoid duplicating code? The only difference is between the "<=" here and the "<" there. I think the "<=" here may be a little better. > + return false; > + > + return !strcmp(name + len - suffix_len, MAYBE_NULL_SUFFIX); > +} > + > +/* Return the type info of a stub function, if it exists. > + * > + * The name of the 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 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 * I think there is double spaces. > +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 *t, *func_proto; > + s32 btf_id; > + > + snprintf(stub_func_name, MAX_STUB_NAME, "%s__%s", > + st_op_name, member_name); check truncated case. > + btf_id = btf_find_by_name_kind(btf, stub_func_name, BTF_KIND_FUNC); > + if (btf_id < 0) > + return NULL; > + t = btf_type_by_id(btf, btf_id); > + if (!t) > + return NULL; > + func_proto = btf_type_by_id(btf, t->type); nit. directly "return btf_type_by_id(btf, t->type);" > + > + return func_proto; > +} > + > +/* Prepare argument info for every nullable argument of a member of a > + * struct_ops type. > + * > + * Initialize a struct bpf_struct_ops_member_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_member_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()) > + * > + * member_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_member_arg_info *member_arg_info) > +{ > + const struct btf_type *stub_func_proto, *pointed_type; > + const struct btf_param *args, *member_args; > + struct bpf_ctx_arg_aux *arg_info, *ai_buf; > + u32 nargs, arg_no, arg_info_cnt = 0; > + const char *arg_name; > + 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; > + > + args = btf_params(stub_func_proto); > + nargs = btf_type_vlen(stub_func_proto); > + if (nargs != btf_type_vlen(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; > + } > + > + member_args = btf_params(func_proto); hmm... the "member_args" naming makes me come back here a few times to figure out "member_args" is the original func_proto or the stub func_proto. How about using a similar convention like you did for func_proto: "func_proto" means the original func_proto and "stub_func_proto" means the stub func_proto, so something like: "args" means the args of original func_proto and "stub_args" means the args of the stub_func_proto ? > + > + ai_buf = kcalloc(nargs, sizeof(*ai_buf), GFP_KERNEL); hmm... instead of ai, lets use a fuller name here like arg_info_buf. > + if (!ai_buf) > + return -ENOMEM; > + > + for (arg_no = 0; arg_no < nargs; arg_no++) { > + /* Skip arguments that is not suffixed with > + * "__nullable". > + */ > + arg_name = btf_name_by_offset(btf, > + args[arg_no].name_off); > + if (!match_nullable_suffix(arg_name)) > + continue; > + > + /* Should be a pointer to struct, array, scalar, or enum */ > + pointed_type = btf_type_resolve_ptr(btf, > + member_args[arg_no].type, > + &arg_btf_id); > + if (!pointed_type || > + !btf_type_is_struct(pointed_type)) > + goto err_out; > + > + offset = btf_ctx_arg_offset(btf, stub_func_proto, arg_no); The original "func_proto" should be used here. > + if (offset < 0) > + goto err_out; > + > + /* Fill the information of the new argument */ > + arg_info = ai_buf + arg_info_cnt++; nit. just init arg_info = arg_info_buf and advance the arg_info++ and arg_info_cnt++ after the offset assignment below. > + 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; > + } > + > + if (arg_info_cnt) { > + member_arg_info->arg_info = ai_buf; > + member_arg_info->arg_info_cnt = arg_info_cnt; > + } else { > + kfree(ai_buf); > + } > + > + return 0; > + > +err_out: > + kfree(ai_buf); > + > + return -EINVAL; > +} > + > 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_member_arg_info *member_arg_info; > struct bpf_struct_ops *st_ops = st_ops_desc->st_ops; > 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 +305,11 @@ 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; > > + member_arg_info = kcalloc(btf_type_vlen(t), sizeof(*member_arg_info), > + GFP_KERNEL); > + if (!member_arg_info) > + return -ENOMEM; > + > for_each_member(i, t, member) { > const struct btf_type *func_proto; > > @@ -167,32 +317,44 @@ 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, > + member_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; > @@ -200,7 +362,16 @@ int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc, > st_ops_desc->value_id = value_id; > st_ops_desc->value_type = btf_type_by_id(btf, value_id); > > + st_ops_desc->member_arg_info = member_arg_info; > + > return 0; > + > +errout: > + while (i > 0) > + kfree(member_arg_info[--i].arg_info); > + kfree(member_arg_info); > + > + 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 aa72674114af..6df390ade2c0 100644 > --- a/kernel/bpf/btf.c > +++ b/kernel/bpf/btf.c > @@ -1699,6 +1699,21 @@ 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; > + struct bpf_struct_ops_member_arg_info *ma_info; Please try to stay consistent with the variable naming in the same patch. The other of this patch is using the "member_arg_info" name. May be just use "arg_infos" everywhere. > + int i, j; > + > + if (!tab) > + return; > + > + for (i = 0; i < tab->cnt; i++) { > + ma_info = tab->ops[i].member_arg_info; > + if (!ma_info) > + continue; > + > + for (j = 0; j < btf_type_vlen(tab->ops[i].type); j++) > + kfree(ma_info[j].arg_info); > + kfree(ma_info); Lets refactor this part out to "bpf_struct_ops_desc_release(struct bpf_struct_ops_desc *)" such that it can be reused with the "errout" path of the "bpf_struct_ops_desc_init()" above. > + } > > kfree(tab); > btf->struct_ops_tab = NULL; > @@ -6130,6 +6145,31 @@ 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 */ > + if (arg_no > nargs) > + 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; > + 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 64fa188d00ad..8d7e761cda0d 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -20433,6 +20433,12 @@ 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->member_arg_info[member_idx].arg_info; > + prog->aux->ctx_arg_info_size = > + st_ops_desc->member_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;
On 2/7/24 12:45, Martin KaFai Lau wrote: > On 2/5/24 10:38 PM, thinker.li@gmail.com wrote: >> From: Kui-Feng Lee <thinker.li@gmail.com> >> >> 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 "<st_op_type>__<operator name>". 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. >> >> Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com> >> --- >> include/linux/bpf.h | 18 ++++ >> kernel/bpf/bpf_struct_ops.c | 185 ++++++++++++++++++++++++++++++++++-- >> kernel/bpf/btf.c | 40 ++++++++ >> kernel/bpf/verifier.c | 6 ++ >> 4 files changed, 242 insertions(+), 7 deletions(-) >> >> diff --git a/include/linux/bpf.h b/include/linux/bpf.h >> index 9a2ee9456989..29d9ec1c4fd9 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 the member >> is not >> + * an operator (function pointer). The "arg_info" field will be >> assigned to >> + * prog->aux->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->arg_info to find the >> + * corresponding entry for an given argument. >> + */ >> +struct bpf_struct_ops_member_arg_info { > > nit. Shorten it to bpf_struct_ops_arg_info. Sure! > >> + struct bpf_ctx_arg_aux *arg_info; >> + u32 arg_info_cnt; >> +}; >> + >> 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_member_arg_info *member_arg_info; > > nit. Same here on the struct's field name. s/member_arg_info/arg_info(s)/. > Sure! >> }; >> enum bpf_struct_ops_state { >> @@ -2500,6 +2516,8 @@ int bpf_prog_test_run_sk_lookup(struct bpf_prog >> *prog, >> int bpf_prog_test_run_nf(struct bpf_prog *prog, >> const union bpf_attr *kattr, >> union bpf_attr __user *uattr); >> +int btf_ctx_arg_offset(struct btf *btf, const struct btf_type >> *func_proto, >> + u32 arg_no); > > This should be in btf.h. Its implementation is also in btf.c in this patch. Got it! I just followed btf_ctx_access(). But, moving to btf.h make sense. > >> 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/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c >> index f98f580de77a..0db7e12a9244 100644 >> --- a/kernel/bpf/bpf_struct_ops.c >> +++ b/kernel/bpf/bpf_struct_ops.c >> @@ -116,17 +116,162 @@ static bool is_valid_value_type(struct btf >> *btf, s32 value_id, >> return true; >> } >> +#define MAYBE_NULL_SUFFIX "__nullable" >> +#define MAX_STUB_NAME 128 >> + >> +static bool match_nullable_suffix(const char *name) >> +{ >> + int suffix_len, len; >> + >> + if (!name) >> + return false; >> + >> + suffix_len = sizeof(MAYBE_NULL_SUFFIX) - 1; >> + len = strlen(name); >> + if (len <= suffix_len) > > This function looks almost the same as __kfunc_param_match_suffix. How > about refactor __kfunc_param_match_suffix (to btf.c?) and resue here to > avoid duplicating code? Sure! > > The only difference is between the "<=" here and the "<" there. I think > the "<=" here may be a little better. > >> + return false; >> + >> + return !strcmp(name + len - suffix_len, MAYBE_NULL_SUFFIX); >> +} >> + >> +/* Return the type info of a stub function, if it exists. >> + * >> + * The name of the 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 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 * > > I think there is double spaces. > >> +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 *t, *func_proto; >> + s32 btf_id; >> + >> + snprintf(stub_func_name, MAX_STUB_NAME, "%s__%s", >> + st_op_name, member_name); > > check truncated case. Sure! > >> + btf_id = btf_find_by_name_kind(btf, stub_func_name, BTF_KIND_FUNC); >> + if (btf_id < 0) >> + return NULL; >> + t = btf_type_by_id(btf, btf_id); >> + if (!t) >> + return NULL; >> + func_proto = btf_type_by_id(btf, t->type); > > nit. directly "return btf_type_by_id(btf, t->type);" > >> + >> + return func_proto; >> +} >> + >> +/* Prepare argument info for every nullable argument of a member of a >> + * struct_ops type. >> + * >> + * Initialize a struct bpf_struct_ops_member_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_member_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()) >> + * >> + * member_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_member_arg_info *member_arg_info) >> +{ >> + const struct btf_type *stub_func_proto, *pointed_type; >> + const struct btf_param *args, *member_args; >> + struct bpf_ctx_arg_aux *arg_info, *ai_buf; >> + u32 nargs, arg_no, arg_info_cnt = 0; >> + const char *arg_name; >> + 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; >> + >> + args = btf_params(stub_func_proto); >> + nargs = btf_type_vlen(stub_func_proto); >> + if (nargs != btf_type_vlen(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; >> + } >> + >> + member_args = btf_params(func_proto); > > hmm... the "member_args" naming makes me come back here a few times to > figure out "member_args" is the original func_proto or the stub func_proto. > > How about using a similar convention like you did for func_proto: > "func_proto" means the original func_proto and "stub_func_proto" means > the stub func_proto, > > so something like: > > "args" means the args of original func_proto and > "stub_args" means the args of the stub_func_proto ? ok! I will rename all member_*. > >> + >> + ai_buf = kcalloc(nargs, sizeof(*ai_buf), GFP_KERNEL); > > hmm... instead of ai, lets use a fuller name here like arg_info_buf. > >> + if (!ai_buf) >> + return -ENOMEM; >> + >> + for (arg_no = 0; arg_no < nargs; arg_no++) { >> + /* Skip arguments that is not suffixed with >> + * "__nullable". >> + */ >> + arg_name = btf_name_by_offset(btf, >> + args[arg_no].name_off); >> + if (!match_nullable_suffix(arg_name)) >> + continue; >> + >> + /* Should be a pointer to struct, array, scalar, or enum */ >> + pointed_type = btf_type_resolve_ptr(btf, >> + member_args[arg_no].type, >> + &arg_btf_id); >> + if (!pointed_type || >> + !btf_type_is_struct(pointed_type)) >> + goto err_out; >> + >> + offset = btf_ctx_arg_offset(btf, stub_func_proto, arg_no); > > The original "func_proto" should be used here. Right! > >> + if (offset < 0) >> + goto err_out; >> + >> + /* Fill the information of the new argument */ >> + arg_info = ai_buf + arg_info_cnt++; > > nit. just init arg_info = arg_info_buf and advance the arg_info++ and > arg_info_cnt++ after the offset assignment below. > >> + 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; >> + } >> + >> + if (arg_info_cnt) { >> + member_arg_info->arg_info = ai_buf; >> + member_arg_info->arg_info_cnt = arg_info_cnt; >> + } else { >> + kfree(ai_buf); >> + } >> + >> + return 0; >> + >> +err_out: >> + kfree(ai_buf); >> + >> + return -EINVAL; >> +} >> + >> 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_member_arg_info *member_arg_info; >> struct bpf_struct_ops *st_ops = st_ops_desc->st_ops; >> 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 +305,11 @@ 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; >> + member_arg_info = kcalloc(btf_type_vlen(t), >> sizeof(*member_arg_info), >> + GFP_KERNEL); >> + if (!member_arg_info) >> + return -ENOMEM; >> + >> for_each_member(i, t, member) { >> const struct btf_type *func_proto; >> @@ -167,32 +317,44 @@ 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, >> + member_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; >> @@ -200,7 +362,16 @@ int bpf_struct_ops_desc_init(struct >> bpf_struct_ops_desc *st_ops_desc, >> st_ops_desc->value_id = value_id; >> st_ops_desc->value_type = btf_type_by_id(btf, value_id); >> + st_ops_desc->member_arg_info = member_arg_info; >> + >> return 0; >> + >> +errout: >> + while (i > 0) >> + kfree(member_arg_info[--i].arg_info); >> + kfree(member_arg_info); >> + >> + 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 aa72674114af..6df390ade2c0 100644 >> --- a/kernel/bpf/btf.c >> +++ b/kernel/bpf/btf.c >> @@ -1699,6 +1699,21 @@ 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; >> + struct bpf_struct_ops_member_arg_info *ma_info; > > Please try to stay consistent with the variable naming in the same > patch. The other of this patch is using the "member_arg_info" name. > > May be just use "arg_infos" everywhere. I will rename all member_*. > >> + int i, j; >> + >> + if (!tab) >> + return; >> + >> + for (i = 0; i < tab->cnt; i++) { >> + ma_info = tab->ops[i].member_arg_info; >> + if (!ma_info) >> + continue; >> + >> + for (j = 0; j < btf_type_vlen(tab->ops[i].type); j++) >> + kfree(ma_info[j].arg_info); >> + kfree(ma_info); > > > Lets refactor this part out to "bpf_struct_ops_desc_release(struct > bpf_struct_ops_desc *)" such that it can be reused with the "errout" > path of the "bpf_struct_ops_desc_init()" above. Sure! > > >> + } >> kfree(tab); >> btf->struct_ops_tab = NULL; >> @@ -6130,6 +6145,31 @@ 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 */ >> + if (arg_no > nargs) >> + 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; >> + 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 64fa188d00ad..8d7e761cda0d 100644 >> --- a/kernel/bpf/verifier.c >> +++ b/kernel/bpf/verifier.c >> @@ -20433,6 +20433,12 @@ 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->member_arg_info[member_idx].arg_info; >> + prog->aux->ctx_arg_info_size = >> + st_ops_desc->member_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; >
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 9a2ee9456989..29d9ec1c4fd9 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 the member is not + * an operator (function pointer). The "arg_info" field will be assigned to + * prog->aux->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->arg_info to find the + * corresponding entry for an given argument. + */ +struct bpf_struct_ops_member_arg_info { + struct bpf_ctx_arg_aux *arg_info; + u32 arg_info_cnt; +}; + 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_member_arg_info *member_arg_info; }; enum bpf_struct_ops_state { @@ -2500,6 +2516,8 @@ int bpf_prog_test_run_sk_lookup(struct bpf_prog *prog, int bpf_prog_test_run_nf(struct bpf_prog *prog, const union bpf_attr *kattr, union bpf_attr __user *uattr); +int btf_ctx_arg_offset(struct btf *btf, const struct btf_type *func_proto, + u32 arg_no); 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/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c index f98f580de77a..0db7e12a9244 100644 --- a/kernel/bpf/bpf_struct_ops.c +++ b/kernel/bpf/bpf_struct_ops.c @@ -116,17 +116,162 @@ static bool is_valid_value_type(struct btf *btf, s32 value_id, return true; } +#define MAYBE_NULL_SUFFIX "__nullable" +#define MAX_STUB_NAME 128 + +static bool match_nullable_suffix(const char *name) +{ + int suffix_len, len; + + if (!name) + return false; + + suffix_len = sizeof(MAYBE_NULL_SUFFIX) - 1; + len = strlen(name); + if (len <= suffix_len) + return false; + + return !strcmp(name + len - suffix_len, MAYBE_NULL_SUFFIX); +} + +/* Return the type info of a stub function, if it exists. + * + * The name of the 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 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 *t, *func_proto; + s32 btf_id; + + snprintf(stub_func_name, MAX_STUB_NAME, "%s__%s", + st_op_name, member_name); + btf_id = btf_find_by_name_kind(btf, stub_func_name, BTF_KIND_FUNC); + if (btf_id < 0) + return NULL; + t = btf_type_by_id(btf, btf_id); + if (!t) + return NULL; + func_proto = btf_type_by_id(btf, t->type); + + return func_proto; +} + +/* Prepare argument info for every nullable argument of a member of a + * struct_ops type. + * + * Initialize a struct bpf_struct_ops_member_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_member_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()) + * + * member_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_member_arg_info *member_arg_info) +{ + const struct btf_type *stub_func_proto, *pointed_type; + const struct btf_param *args, *member_args; + struct bpf_ctx_arg_aux *arg_info, *ai_buf; + u32 nargs, arg_no, arg_info_cnt = 0; + const char *arg_name; + 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; + + args = btf_params(stub_func_proto); + nargs = btf_type_vlen(stub_func_proto); + if (nargs != btf_type_vlen(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; + } + + member_args = btf_params(func_proto); + + ai_buf = kcalloc(nargs, sizeof(*ai_buf), GFP_KERNEL); + if (!ai_buf) + return -ENOMEM; + + for (arg_no = 0; arg_no < nargs; arg_no++) { + /* Skip arguments that is not suffixed with + * "__nullable". + */ + arg_name = btf_name_by_offset(btf, + args[arg_no].name_off); + if (!match_nullable_suffix(arg_name)) + continue; + + /* Should be a pointer to struct, array, scalar, or enum */ + pointed_type = btf_type_resolve_ptr(btf, + member_args[arg_no].type, + &arg_btf_id); + if (!pointed_type || + !btf_type_is_struct(pointed_type)) + goto err_out; + + offset = btf_ctx_arg_offset(btf, stub_func_proto, arg_no); + if (offset < 0) + goto err_out; + + /* Fill the information of the new argument */ + arg_info = ai_buf + arg_info_cnt++; + 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; + } + + if (arg_info_cnt) { + member_arg_info->arg_info = ai_buf; + member_arg_info->arg_info_cnt = arg_info_cnt; + } else { + kfree(ai_buf); + } + + return 0; + +err_out: + kfree(ai_buf); + + return -EINVAL; +} + 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_member_arg_info *member_arg_info; struct bpf_struct_ops *st_ops = st_ops_desc->st_ops; 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 +305,11 @@ 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; + member_arg_info = kcalloc(btf_type_vlen(t), sizeof(*member_arg_info), + GFP_KERNEL); + if (!member_arg_info) + return -ENOMEM; + for_each_member(i, t, member) { const struct btf_type *func_proto; @@ -167,32 +317,44 @@ 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, + member_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; @@ -200,7 +362,16 @@ int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc, st_ops_desc->value_id = value_id; st_ops_desc->value_type = btf_type_by_id(btf, value_id); + st_ops_desc->member_arg_info = member_arg_info; + return 0; + +errout: + while (i > 0) + kfree(member_arg_info[--i].arg_info); + kfree(member_arg_info); + + 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 aa72674114af..6df390ade2c0 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -1699,6 +1699,21 @@ 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; + struct bpf_struct_ops_member_arg_info *ma_info; + int i, j; + + if (!tab) + return; + + for (i = 0; i < tab->cnt; i++) { + ma_info = tab->ops[i].member_arg_info; + if (!ma_info) + continue; + + for (j = 0; j < btf_type_vlen(tab->ops[i].type); j++) + kfree(ma_info[j].arg_info); + kfree(ma_info); + } kfree(tab); btf->struct_ops_tab = NULL; @@ -6130,6 +6145,31 @@ 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 */ + if (arg_no > nargs) + 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; + 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 64fa188d00ad..8d7e761cda0d 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -20433,6 +20433,12 @@ 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->member_arg_info[member_idx].arg_info; + prog->aux->ctx_arg_info_size = + st_ops_desc->member_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;