From patchwork Wed Oct 16 07:09:54 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Song Liu X-Patchwork-Id: 13837818 X-Patchwork-Delegate: bpf@iogearbox.net Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 1FF5D433CE; Wed, 16 Oct 2024 07:10:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729062612; cv=none; b=pgYRiR+C8g7rqvpMLJCxKziXrxpi8a9hXmQwCjDlpleEkC/w5Ae67zn6j/O8QLFffYdnalHR4bzgVTTDyDEWejOqDhW8RMOv5Mgro66NzTsD+/VNIPGsoWl09RUzbiGREyaIQMsWlUi5+6SqeKJuJ7PzV6BZSXnX3mmmlIprr1M= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729062612; c=relaxed/simple; bh=qjkUQnj7X1HSIZmhhRqEIfNPxQwTNUIMw0n/JwW80xA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=GxXJ+1JeMpOaNvlxtyaJ+r6/Fmb67FSoOPpD7tZw1zCL6VXMsDAoiCSyP/j25/K4/fasgEGyEr81OXSe1hwAJv3uOXvYqAlJgVdz9fJtIe9v3BEfbnX1Ra2KZiVvvp7qm0ppu/SXLgB9Bfwhy5MWNVMv720b79AWNPxRo+9zyHk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cs1JD7F3; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="cs1JD7F3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 41F7FC4CEC5; Wed, 16 Oct 2024 07:10:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1729062611; bh=qjkUQnj7X1HSIZmhhRqEIfNPxQwTNUIMw0n/JwW80xA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cs1JD7F3Ya0WX27sQO00tIeWSoSSVq2+1upGoN9hEAxGW+57HboIXbHAs0l/u8jSV xS4+Lv42AXmH3SK13nRJSLOeQPUJSyGIctZ6uYYgR6yu8w8y2Xf440NehS4AQyH+XR 0dCWS9Prgf3IGUOagl1rwO/Jag5/EvevvaD4IlM6oIZUE0SpK/Zo/AWujxPfbckeup phn9+0yxNdhpmfwFtWTroAM9TfVz63BB10c8fzEfEBhw5hUz5aonFdWBx1ZM4cb2v8 omGqXZY2XtHiQP0U/vJ/A4gcSq2aaEPEE51e92nymdPLZi4Qo2XjtmAvd0n3lrYgz6 IPxDa5QzCypOw== From: Song Liu To: bpf@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: kernel-team@meta.com, andrii@kernel.org, eddyz87@gmail.com, ast@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, kpsingh@kernel.org, mattbobrowski@google.com, Song Liu Subject: [PATCH v2 bpf-next 1/2] fs/xattr: bpf: Introduce security.bpf xattr name prefix Date: Wed, 16 Oct 2024 00:09:54 -0700 Message-ID: <20241016070955.375923-2-song@kernel.org> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20241016070955.375923-1-song@kernel.org> References: <20241016070955.375923-1-song@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net Introduct new xattr name prefix security.bpf, and enable reading these xattrs from bpf kfuncs bpf_get_[file|dentry]_xattr(). Note that "security.bpf" could be the name of the xattr or the prefix of the name. For example, both "security.bpf" and "security.bpf.xxx" are valid xattr name; while "security.bpfxxx" is not valid. As we are on it, correct the comments for return value of bpf_get_[file|dentry]_xattr(), i.e. return length the xattr value on successl. Signed-off-by: Song Liu Acked-by: Christian Brauner --- fs/bpf_fs_kfuncs.c | 29 ++++++++++++++++++++++++----- include/uapi/linux/xattr.h | 4 ++++ 2 files changed, 28 insertions(+), 5 deletions(-) diff --git a/fs/bpf_fs_kfuncs.c b/fs/bpf_fs_kfuncs.c index 3fe9f59ef867..be78a13f1d82 100644 --- a/fs/bpf_fs_kfuncs.c +++ b/fs/bpf_fs_kfuncs.c @@ -93,6 +93,23 @@ __bpf_kfunc int bpf_path_d_path(struct path *path, char *buf, size_t buf__sz) return len; } +static bool bpf_xattr_name_allowed(const char *name__str) +{ + /* Allow xattr names with user. prefix */ + if (!strncmp(name__str, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) + return true; + + /* Allow security.bpf. prefix or just security.bpf */ + if (!strncmp(name__str, XATTR_NAME_BPF_LSM, XATTR_NAME_BPF_LSM_LEN) && + (name__str[XATTR_NAME_BPF_LSM_LEN] == '\0' || + name__str[XATTR_NAME_BPF_LSM_LEN] == '.')) { + return true; + } + + /* Disallow anything else */ + return false; +} + /** * bpf_get_dentry_xattr - get xattr of a dentry * @dentry: dentry to get xattr from @@ -101,9 +118,10 @@ __bpf_kfunc int bpf_path_d_path(struct path *path, char *buf, size_t buf__sz) * * Get xattr *name__str* of *dentry* and store the output in *value_ptr*. * - * For security reasons, only *name__str* with prefix "user." is allowed. + * For security reasons, only *name__str* with prefix "user." or + * "security.bpf" is allowed. * - * Return: 0 on success, a negative value on error. + * Return: length of the xattr value on success, a negative value on error. */ __bpf_kfunc int bpf_get_dentry_xattr(struct dentry *dentry, const char *name__str, struct bpf_dynptr *value_p) @@ -117,7 +135,7 @@ __bpf_kfunc int bpf_get_dentry_xattr(struct dentry *dentry, const char *name__st if (WARN_ON(!inode)) return -EINVAL; - if (strncmp(name__str, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) + if (!bpf_xattr_name_allowed(name__str)) return -EPERM; value_len = __bpf_dynptr_size(value_ptr); @@ -139,9 +157,10 @@ __bpf_kfunc int bpf_get_dentry_xattr(struct dentry *dentry, const char *name__st * * Get xattr *name__str* of *file* and store the output in *value_ptr*. * - * For security reasons, only *name__str* with prefix "user." is allowed. + * For security reasons, only *name__str* with prefix "user." or + * "security.bpf" is allowed. * - * Return: 0 on success, a negative value on error. + * Return: length of the xattr value on success, a negative value on error. */ __bpf_kfunc int bpf_get_file_xattr(struct file *file, const char *name__str, struct bpf_dynptr *value_p) diff --git a/include/uapi/linux/xattr.h b/include/uapi/linux/xattr.h index 9463db2dfa9d..166ef2f1f1b3 100644 --- a/include/uapi/linux/xattr.h +++ b/include/uapi/linux/xattr.h @@ -76,6 +76,10 @@ #define XATTR_CAPS_SUFFIX "capability" #define XATTR_NAME_CAPS XATTR_SECURITY_PREFIX XATTR_CAPS_SUFFIX +#define XATTR_BPF_LSM_SUFFIX "bpf" +#define XATTR_NAME_BPF_LSM (XATTR_SECURITY_PREFIX XATTR_BPF_LSM_SUFFIX) +#define XATTR_NAME_BPF_LSM_LEN (sizeof(XATTR_NAME_BPF_LSM) - 1) + #define XATTR_POSIX_ACL_ACCESS "posix_acl_access" #define XATTR_NAME_POSIX_ACL_ACCESS XATTR_SYSTEM_PREFIX XATTR_POSIX_ACL_ACCESS #define XATTR_POSIX_ACL_DEFAULT "posix_acl_default"