From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 EE1F28F63 for ; Thu, 19 Oct 2023 00:36:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="D8bdcP7+" Received: from out-201.mta1.migadu.com (out-201.mta1.migadu.com [95.215.58.201]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 468C0FE for ; Wed, 18 Oct 2023 17:36:16 -0700 (PDT) Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1697675774; 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=svfeXZnS4yc+/OvMqdJe5A9oe+3GQEVWS3h6543MKms=; b=D8bdcP7+m1hHdTEZj55585qB5SSm+dVWBAyncS5fff3A0SUlihTUIHg4id7+bC7nVhQS0k XVBL/Xse2A583G2G0iIzSMtWhSRXjBBZsQ1/eBYSxmv0Poa9h0g9JOSvtRX6kcad+cLLCi WIM9FXGGHRv2Gcg9IaZkibg4qd14THs= Date: Wed, 18 Oct 2023 17:36:10 -0700 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf-next v5 3/9] bpf: hold module for bpf_struct_ops_map. 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, drosen@google.com References: <20231017162306.176586-1-thinker.li@gmail.com> <20231017162306.176586-4-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: <20231017162306.176586-4-thinker.li@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 10/17/23 9:23 AM, thinker.li@gmail.com wrote: > From: Kui-Feng Lee > > To ensure that a module remains accessible whenever a struct_ops object of > a struct_ops type provided by the module is still in use. > > Signed-off-by: Kui-Feng Lee > --- > include/linux/bpf.h | 1 + > kernel/bpf/bpf_struct_ops.c | 21 ++++++++++++++++++--- > 2 files changed, 19 insertions(+), 3 deletions(-) > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > index e6a648af2daa..1e1647c8b0ce 100644 > --- a/include/linux/bpf.h > +++ b/include/linux/bpf.h > @@ -1627,6 +1627,7 @@ struct bpf_struct_ops { > int (*update)(void *kdata, void *old_kdata); > int (*validate)(void *kdata); > struct btf *btf; > + struct module *owner; > const struct btf_type *type; > const struct btf_type *value_type; > const char *name; > diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c > index 7758f66ad734..b561245fe235 100644 > --- a/kernel/bpf/bpf_struct_ops.c > +++ b/kernel/bpf/bpf_struct_ops.c > @@ -112,6 +112,7 @@ static const struct btf_type *module_type; > > static void bpf_struct_ops_init_one(struct bpf_struct_ops *st_ops, > struct btf *btf, > + struct module *owner, > struct bpf_verifier_log *log) > { > const struct btf_member *member; > @@ -186,6 +187,7 @@ static void bpf_struct_ops_init_one(struct bpf_struct_ops *st_ops, > st_ops->name); > } else { > st_ops->btf = btf; > + st_ops->owner = owner; I suspect it will turn out to be just "st_ops->owner = st_ops->owner;" in a latter patch. st_ops->owner should have already been initialized (with THIS_MODULE?). > st_ops->type_id = type_id; > st_ops->type = t; > st_ops->value_id = value_id; > @@ -193,6 +195,7 @@ static void bpf_struct_ops_init_one(struct bpf_struct_ops *st_ops, > value_id); > } > } > + nit. extra newline. > } > > void bpf_struct_ops_init(struct btf *btf, struct bpf_verifier_log *log) > @@ -215,7 +218,7 @@ void bpf_struct_ops_init(struct btf *btf, struct bpf_verifier_log *log) > > for (i = 0; i < ARRAY_SIZE(bpf_struct_ops); i++) { > st_ops = bpf_struct_ops[i]; > - bpf_struct_ops_init_one(st_ops, btf, log); > + bpf_struct_ops_init_one(st_ops, btf, NULL, log); > } > } > > @@ -630,6 +633,7 @@ static void __bpf_struct_ops_map_free(struct bpf_map *map) > bpf_jit_uncharge_modmem(PAGE_SIZE); > } > bpf_map_area_free(st_map->uvalue); > + module_put(st_map->st_ops->owner); > bpf_map_area_free(st_map); > } > > @@ -676,9 +680,18 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr) > if (!st_ops) > return ERR_PTR(-ENOTSUPP); > > + /* If st_ops->owner is NULL, it means the struct_ops is > + * statically defined in the kernel. We don't need to > + * take a refcount on it. > + */ > + if (st_ops->owner && !btf_try_get_module(st_ops->btf)) This just came to my mind. Is the module refcnt needed during map alloc/free or it could be done during the reg/unreg instead? > + return ERR_PTR(-EINVAL); > + > vt = st_ops->value_type; > - if (attr->value_size != vt->size) > + if (attr->value_size != vt->size) { > + module_put(st_ops->owner); > return ERR_PTR(-EINVAL); > + } > > t = st_ops->type; > > @@ -689,8 +702,10 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr) > (vt->size - sizeof(struct bpf_struct_ops_value)); > > st_map = bpf_map_area_alloc(st_map_size, NUMA_NO_NODE); > - if (!st_map) > + if (!st_map) { > + module_put(st_ops->owner); > return ERR_PTR(-ENOMEM); > + } > > st_map->st_ops = st_ops; > map = &st_map->map;