From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C6215E7AD52 for ; Tue, 3 Oct 2023 14:17:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238758AbjJCORi (ORCPT ); Tue, 3 Oct 2023 10:17:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45786 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234771AbjJCORh (ORCPT ); Tue, 3 Oct 2023 10:17:37 -0400 X-Greylist: delayed 487 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Tue, 03 Oct 2023 07:17:33 PDT Received: from smtp-1908.mail.infomaniak.ch (smtp-1908.mail.infomaniak.ch [IPv6:2001:1600:4:17::1908]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D49459E for ; Tue, 3 Oct 2023 07:17:33 -0700 (PDT) Received: from smtp-2-0000.mail.infomaniak.ch (unknown [10.5.36.107]) by smtp-3-3000.mail.infomaniak.ch (Postfix) with ESMTPS id 4S0KSj1xYdzMq9nw; Tue, 3 Oct 2023 14:09:25 +0000 (UTC) Received: from unknown by smtp-2-0000.mail.infomaniak.ch (Postfix) with ESMTPA id 4S0KSg4WSzzMppDP; Tue, 3 Oct 2023 16:09:23 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=digikod.net; s=20191114; t=1696342165; bh=m95QP7+DMGADAxzuHLGbl+2nWXxMVw5xU2PPZKu1Yok=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Pt6yGYXxtlS9ZH0Ws2AYs76zafsRTtrLLom5XSJ/4UhEfpw/dbrAIZ2H7cj5F3vEZ q5gAxcUI92vDrvJy+kQhViVaX9g9vJm5JmTUohGwtL2puiFnD2OBLI+wCJbV5d2NoN esIeOC9fbyKHinweVnCQSD0ZobBpxDshVIrXGhxI= Date: Tue, 3 Oct 2023 16:09:23 +0200 From: =?utf-8?Q?Micka=C3=ABl_Sala=C3=BCn?= To: Casey Schaufler Cc: paul@paul-moore.com, linux-security-module@vger.kernel.org, jmorris@namei.org, serge@hallyn.com, keescook@chromium.org, john.johansen@canonical.com, penguin-kernel@i-love.sakura.ne.jp, stephen.smalley.work@gmail.com, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org Subject: Re: [PATCH v15 04/11] LSM: syscalls for current process attributes Message-ID: <20231003.kooghohS2Aiz@digikod.net> References: <20230912205658.3432-1-casey@schaufler-ca.com> <20230912205658.3432-5-casey@schaufler-ca.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20230912205658.3432-5-casey@schaufler-ca.com> X-Infomaniak-Routing: alpha Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Tue, Sep 12, 2023 at 01:56:49PM -0700, Casey Schaufler wrote: > Create a system call lsm_get_self_attr() to provide the security > module maintained attributes of the current process. > Create a system call lsm_set_self_attr() to set a security > module maintained attribute of the current process. > Historically these attributes have been exposed to user space via > entries in procfs under /proc/self/attr. > > The attribute value is provided in a lsm_ctx structure. The structure > identifies the size of the attribute, and the attribute value. The format > of the attribute value is defined by the security module. A flags field > is included for LSM specific information. It is currently unused and must > be 0. The total size of the data, including the lsm_ctx structure and any > padding, is maintained as well. > > struct lsm_ctx { > __u64 id; > __u64 flags; > __u64 len; > __u64 ctx_len; > __u8 ctx[]; > }; > > Two new LSM hooks are used to interface with the LSMs. > security_getselfattr() collects the lsm_ctx values from the > LSMs that support the hook, accounting for space requirements. > security_setselfattr() identifies which LSM the attribute is > intended for and passes it along. > > Signed-off-by: Casey Schaufler > Reviewed-by: Kees Cook > Reviewed-by: Serge Hallyn > Reviewed-by: John Johansen > --- > Documentation/userspace-api/lsm.rst | 70 +++++++++++++ > include/linux/lsm_hook_defs.h | 4 + > include/linux/lsm_hooks.h | 1 + > include/linux/security.h | 19 ++++ > include/linux/syscalls.h | 5 + > include/uapi/linux/lsm.h | 36 +++++++ > kernel/sys_ni.c | 2 + > security/Makefile | 1 + > security/lsm_syscalls.c | 57 +++++++++++ > security/security.c | 152 ++++++++++++++++++++++++++++ > 10 files changed, 347 insertions(+) > create mode 100644 Documentation/userspace-api/lsm.rst > create mode 100644 security/lsm_syscalls.c > > diff --git a/security/security.c b/security/security.c > index a3489c04b783..0d179750d964 100644 > --- a/security/security.c > +++ b/security/security.c > @@ -3837,6 +3837,158 @@ void security_d_instantiate(struct dentry *dentry, struct inode *inode) > } > EXPORT_SYMBOL(security_d_instantiate); > > +/* > + * Please keep this in sync with it's counterpart in security/lsm_syscalls.c > + */ > + > +/** > + * security_getselfattr - Read an LSM attribute of the current process. > + * @attr: which attribute to return > + * @uctx: the user-space destination for the information, or NULL > + * @size: pointer to the size of space available to receive the data > + * @flags: special handling options. LSM_FLAG_SINGLE indicates that only > + * attributes associated with the LSM identified in the passed @ctx be > + * reported. > + * > + * A NULL value for @uctx can be used to get both the number of attributes > + * and the size of the data. > + * > + * Returns the number of attributes found on success, negative value > + * on error. @size is reset to the total size of the data. > + * If @size is insufficient to contain the data -E2BIG is returned. > + */ > +int security_getselfattr(unsigned int attr, struct lsm_ctx __user *uctx, > + size_t __user *size, u32 flags) > +{ > + struct security_hook_list *hp; > + struct lsm_ctx lctx = { .id = LSM_ID_UNDEF, }; > + u8 __user *base = (u8 __user *)uctx; > + size_t total = 0; > + size_t entrysize; > + size_t left; > + bool toobig = false; > + bool single = false; > + int count = 0; > + int rc; > + > + if (attr == LSM_ATTR_UNDEF) > + return -EINVAL; > + if (size == NULL) > + return -EINVAL; > + if (get_user(left, size)) > + return -EFAULT; > + > + if (flags) { > + /* > + * Only flag supported is LSM_FLAG_SINGLE > + */ > + if (flags != LSM_FLAG_SINGLE) > + return -EINVAL; > + if (uctx && copy_from_user(&lctx, uctx, sizeof(lctx))) I'm not sure if we should return -EINVAL or -EFAULT when uctx == NULL. Because uctx is optional (when LSM_FLAG_SINGLE is not set), I guess -EINVAL is OK. > + return -EFAULT; > + /* > + * If the LSM ID isn't specified it is an error. > + */ > + if (lctx.id == LSM_ID_UNDEF) > + return -EINVAL; > + single = true; > + } > + > + /* > + * In the usual case gather all the data from the LSMs. > + * In the single case only get the data from the LSM specified. > + */ > + hlist_for_each_entry(hp, &security_hook_heads.getselfattr, list) { > + if (single && lctx.id != hp->lsmid->id) > + continue; > + entrysize = left; > + if (base) > + uctx = (struct lsm_ctx __user *)(base + total); > + rc = hp->hook.getselfattr(attr, uctx, &entrysize, flags); > + if (rc == -EOPNOTSUPP) { > + rc = 0; > + continue; > + } > + if (rc == -E2BIG) { > + toobig = true; > + left = 0; > + } else if (rc < 0) > + return rc; > + else > + left -= entrysize; > + > + total += entrysize; > + count += rc; There is a bug if rc == -E2BIG > + if (single) > + break; > + } > + if (put_user(total, size)) > + return -EFAULT; > + if (toobig) > + return -E2BIG; > + if (count == 0) > + return LSM_RET_DEFAULT(getselfattr); > + return count; > +}