From patchwork Thu Nov 7 14:03:04 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Laurent Vivier X-Patchwork-Id: 11232985 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A9B2F1747 for ; Thu, 7 Nov 2019 14:15:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7BE6021D7F for ; Thu, 7 Nov 2019 14:15:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731058AbfKGOO7 (ORCPT ); Thu, 7 Nov 2019 09:14:59 -0500 Received: from mout.kundenserver.de ([212.227.126.135]:41921 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389510AbfKGOOz (ORCPT ); Thu, 7 Nov 2019 09:14:55 -0500 Received: from localhost.localdomain ([78.238.229.36]) by mrelayeu.kundenserver.de (mreue012 [212.227.15.167]) with ESMTPSA (Nemesis) id 1M28O9-1iVCPk2Lyz-002ZYk; Thu, 07 Nov 2019 15:03:10 +0100 From: Laurent Vivier To: linux-kernel@vger.kernel.org Cc: Dmitry Safonov , Henning Schild , linux-fsdevel@vger.kernel.org, James Bottomley , Eric Biederman , linux-api@vger.kernel.org, Andrei Vagin , =?utf-8?q?C=C3=A9dric_Le_Goater?= , Greg Kurz , Jann Horn , containers@lists.linux-foundation.org, Alexander Viro , Jan Kiszka , Laurent Vivier Subject: [PATCH v7 1/1] ns: add binfmt_misc to the user namespace Date: Thu, 7 Nov 2019 15:03:04 +0100 Message-Id: <20191107140304.8426-2-laurent@vivier.eu> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20191107140304.8426-1-laurent@vivier.eu> References: <20191107140304.8426-1-laurent@vivier.eu> MIME-Version: 1.0 X-Provags-ID: V03:K1:4iHpdG1rXpay6u5XOIjiSlQbsHmLFPUeXLo66HYY0tRMmj2W3qP TaPaEMZwVb9DryHf1jwLWA6gHC8Kr0BNIhhM2muxlVrSEfbRn6k2SSGwasZgQ6KMGXJY3wb l4p9ndsmeXzeA19qD0/FVskIuuKbX2+v6QUIQLJYeRqVdR5eYqZ6fA4L8SDOKufy5g3yVcY tUAaRrqDrJcV2ZBPsE6zw== X-Spam-Flag: NO X-UI-Out-Filterresults: notjunk:1;V03:K0:7NnKeG6QPg4=:3/v8s3dqLoZkazhTNhPeSN 32IlaviKqasO02dQrrkH3FnrvMxtHomjdzm9XvAAvHGGrnSN9mb92FS8PrqRyxuUZ0l2hSYRL utwq9RX9CLl7nsusGULi9wnYXEZFionk45zQ32X/pXLAgAARyn/swtPQ4hoqkEWAR7MykJrSq s1ZkBvm0JRYxWCRPPEseEMIjhWmbq0if5STFumJT4WXiSVhOQRkq2nCRJPe2sXCM7Bo70+Uak VT/RYSB3IUVL+CQVMD8eaMnDtlRIom6VIlBq9hWoJeBBa4bUif58Hx6e9mxNxbqQbb8mUmLHU //DPX/wW7O3CWv+pwJmpUNzDyhe5JXjb/n0Qf59tccB/Ew1AZx0Y/NK0VcYysKiS6TtABH+Gn yYcdwpaF/OO+0YE2D8FcMl/JrYFima7IIdUo20/jOM1qeFl3dVAayjEV02nlGYQ8VnZ5oyg7Z 3FgJkkfMlEu05xDm1hTky/8/3GSgK865R12O+21/xEPKwSV2aiw+wDMWVMi0xHAmBtgSVEVXh JXF6BUtbncRedsBtX69nIslxXY/e5lxCqWMUgiR5KTAnvha7xhR6hEnBHFxUz2qXikJTsw8oL vIHjK1Redniv6cK2a1skl3ZA0EYNZO/jznf6fp2BLBRQvI8JIvrBL0pEdGCw8cjKjhW4HqQjw TTS5jstbbDbLUOEbmJqFfsYdXmLeadAzhJqGbSowFt81fTXj8miZ4Qvx9c1bUl7oMpM05+lUu fjrnf1Jes7Gh6hp4PWYJNp+dXeVAL6UD468lRq3hT6Ub3cmh3oChq+g0b135WbyuSGQoW//yX cg9GUEw3Z3Qt0GXwBTzZgvjNl8ubQlPzlft6AUZoYqIZtMc8xy2+DJlAUYD9Sd5KZIPMC1uyh eDLKh41Y5beipYNZIqwg== Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org This patch allows to have a different binfmt_misc configuration for each new user namespace. By default, the binfmt_misc configuration is the one of the previous level, but if the binfmt_misc filesystem is mounted in the new namespace a new empty binfmt instance is created and used in this namespace. For instance, using "unshare" we can start a chroot of another architecture and configure the binfmt_misc interpreter without being root to run the binaries in this chroot. Signed-off-by: Laurent Vivier Acked-by: Andrei Vagin Tested-by: Henning Schild --- fs/binfmt_misc.c | 115 +++++++++++++++++++++++++-------- include/linux/user_namespace.h | 15 +++++ kernel/user.c | 14 ++++ kernel/user_namespace.c | 3 + 4 files changed, 119 insertions(+), 28 deletions(-) diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c index cdb45829354d..ba5f0d2ade96 100644 --- a/fs/binfmt_misc.c +++ b/fs/binfmt_misc.c @@ -40,9 +40,6 @@ enum { VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */ }; -static LIST_HEAD(entries); -static int enabled = 1; - enum {Enabled, Magic}; #define MISC_FMT_PRESERVE_ARGV0 (1 << 31) #define MISC_FMT_OPEN_BINARY (1 << 30) @@ -62,10 +59,7 @@ typedef struct { struct file *interp_file; } Node; -static DEFINE_RWLOCK(entries_lock); static struct file_system_type bm_fs_type; -static struct vfsmount *bm_mnt; -static int entry_count; /* * Max length of the register string. Determined by: @@ -82,18 +76,37 @@ static int entry_count; */ #define MAX_REGISTER_LENGTH 1920 +static struct binfmt_namespace *binfmt_ns(struct user_namespace *ns) +{ + struct binfmt_namespace *b_ns; + + while (ns) { + b_ns = READ_ONCE(ns->binfmt_ns); + if (b_ns) + return b_ns; + ns = ns->parent; + } + /* as the first user namespace is initialized with + * &init_binfmt_ns we should never come here + * but we try to stay safe by logging a warning + * and returning a sane value + */ + WARN_ON_ONCE(1); + return &init_binfmt_ns; +} + /* * Check if we support the binfmt * if we do, return the node, else NULL * locking is done in load_misc_binary */ -static Node *check_file(struct linux_binprm *bprm) +static Node *check_file(struct binfmt_namespace *ns, struct linux_binprm *bprm) { char *p = strrchr(bprm->interp, '.'); struct list_head *l; /* Walk all the registered handlers. */ - list_for_each(l, &entries) { + list_for_each(l, &ns->entries) { Node *e = list_entry(l, Node, list); char *s; int j; @@ -135,17 +148,18 @@ static int load_misc_binary(struct linux_binprm *bprm) struct file *interp_file = NULL; int retval; int fd_binary = -1; + struct binfmt_namespace *ns = binfmt_ns(current_user_ns()); retval = -ENOEXEC; - if (!enabled) + if (!ns->enabled) return retval; /* to keep locking time low, we copy the interpreter string */ - read_lock(&entries_lock); - fmt = check_file(bprm); + read_lock(&ns->entries_lock); + fmt = check_file(ns, bprm); if (fmt) dget(fmt->dentry); - read_unlock(&entries_lock); + read_unlock(&ns->entries_lock); if (!fmt) return retval; @@ -611,19 +625,19 @@ static void bm_evict_inode(struct inode *inode) kfree(e); } -static void kill_node(Node *e) +static void kill_node(struct binfmt_namespace *ns, Node *e) { struct dentry *dentry; - write_lock(&entries_lock); + write_lock(&ns->entries_lock); list_del_init(&e->list); - write_unlock(&entries_lock); + write_unlock(&ns->entries_lock); dentry = e->dentry; drop_nlink(d_inode(dentry)); d_drop(dentry); dput(dentry); - simple_release_fs(&bm_mnt, &entry_count); + simple_release_fs(&ns->bm_mnt, &ns->entry_count); } /* / */ @@ -653,6 +667,9 @@ static ssize_t bm_entry_write(struct file *file, const char __user *buffer, struct dentry *root; Node *e = file_inode(file)->i_private; int res = parse_command(buffer, count); + struct binfmt_namespace *ns; + + ns = binfmt_ns(file->f_path.dentry->d_sb->s_user_ns); switch (res) { case 1: @@ -669,7 +686,7 @@ static ssize_t bm_entry_write(struct file *file, const char __user *buffer, inode_lock(d_inode(root)); if (!list_empty(&e->list)) - kill_node(e); + kill_node(ns, e); inode_unlock(d_inode(root)); break; @@ -695,6 +712,7 @@ static ssize_t bm_register_write(struct file *file, const char __user *buffer, struct inode *inode; struct super_block *sb = file_inode(file)->i_sb; struct dentry *root = sb->s_root, *dentry; + struct binfmt_namespace *ns; int err = 0; e = create_entry(buffer, count); @@ -718,7 +736,9 @@ static ssize_t bm_register_write(struct file *file, const char __user *buffer, if (!inode) goto out2; - err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count); + ns = binfmt_ns(file->f_path.dentry->d_sb->s_user_ns); + err = simple_pin_fs(&bm_fs_type, &ns->bm_mnt, + &ns->entry_count); if (err) { iput(inode); inode = NULL; @@ -727,12 +747,16 @@ static ssize_t bm_register_write(struct file *file, const char __user *buffer, if (e->flags & MISC_FMT_OPEN_FILE) { struct file *f; + const struct cred *old_cred; + old_cred = override_creds(file->f_cred); f = open_exec(e->interpreter); + revert_creds(old_cred); if (IS_ERR(f)) { err = PTR_ERR(f); pr_notice("register: failed to install interpreter file %s\n", e->interpreter); - simple_release_fs(&bm_mnt, &entry_count); + simple_release_fs(&ns->bm_mnt, + &ns->entry_count); iput(inode); inode = NULL; goto out2; @@ -745,9 +769,9 @@ static ssize_t bm_register_write(struct file *file, const char __user *buffer, inode->i_fop = &bm_entry_operations; d_instantiate(dentry, inode); - write_lock(&entries_lock); - list_add(&e->list, &entries); - write_unlock(&entries_lock); + write_lock(&ns->entries_lock); + list_add(&e->list, &ns->entries); + write_unlock(&ns->entries_lock); err = 0; out2: @@ -772,7 +796,9 @@ static const struct file_operations bm_register_operations = { static ssize_t bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) { - char *s = enabled ? "enabled\n" : "disabled\n"; + struct binfmt_namespace *ns = + binfmt_ns(file->f_path.dentry->d_sb->s_user_ns); + char *s = ns->enabled ? "enabled\n" : "disabled\n"; return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s)); } @@ -780,25 +806,28 @@ bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) static ssize_t bm_status_write(struct file *file, const char __user *buffer, size_t count, loff_t *ppos) { + struct binfmt_namespace *ns; int res = parse_command(buffer, count); struct dentry *root; + ns = binfmt_ns(file->f_path.dentry->d_sb->s_user_ns); switch (res) { case 1: /* Disable all handlers. */ - enabled = 0; + ns->enabled = 0; break; case 2: /* Enable all handlers. */ - enabled = 1; + ns->enabled = 1; break; case 3: /* Delete all handlers. */ root = file_inode(file)->i_sb->s_root; inode_lock(d_inode(root)); - while (!list_empty(&entries)) - kill_node(list_first_entry(&entries, Node, list)); + while (!list_empty(&ns->entries)) + kill_node(ns, list_first_entry(&ns->entries, + Node, list)); inode_unlock(d_inode(root)); break; @@ -825,24 +854,53 @@ static const struct super_operations s_ops = { static int bm_fill_super(struct super_block *sb, struct fs_context *fc) { int err; + struct user_namespace *ns = sb->s_user_ns; static const struct tree_descr bm_files[] = { [2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO}, [3] = {"register", &bm_register_operations, S_IWUSR}, /* last one */ {""} }; + /* create a new binfmt namespace + * if we are not in the first user namespace + * but the binfmt namespace is the first one + */ + if (READ_ONCE(ns->binfmt_ns) == NULL) { + struct binfmt_namespace *new_ns; + + new_ns = kmalloc(sizeof(struct binfmt_namespace), + GFP_KERNEL); + if (new_ns == NULL) + return -ENOMEM; + INIT_LIST_HEAD(&new_ns->entries); + new_ns->enabled = 1; + rwlock_init(&new_ns->entries_lock); + new_ns->bm_mnt = NULL; + new_ns->entry_count = 0; + /* ensure new_ns is completely initialized before sharing it */ + smp_wmb(); + WRITE_ONCE(ns->binfmt_ns, new_ns); + } + err = simple_fill_super(sb, BINFMTFS_MAGIC, bm_files); if (!err) sb->s_op = &s_ops; return err; } +static void bm_free(struct fs_context *fc) +{ + if (fc->s_fs_info) + put_user_ns(fc->s_fs_info); +} + static int bm_get_tree(struct fs_context *fc) { - return get_tree_single(fc, bm_fill_super); + return get_tree_keyed(fc, bm_fill_super, get_user_ns(fc->user_ns)); } static const struct fs_context_operations bm_context_ops = { + .free = bm_free, .get_tree = bm_get_tree, }; @@ -861,6 +919,7 @@ static struct file_system_type bm_fs_type = { .owner = THIS_MODULE, .name = "binfmt_misc", .init_fs_context = bm_init_fs_context, + .fs_flags = FS_USERNS_MOUNT, .kill_sb = kill_litter_super, }; MODULE_ALIAS_FS("binfmt_misc"); diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h index fb9f4f799554..16e6f3a97a01 100644 --- a/include/linux/user_namespace.h +++ b/include/linux/user_namespace.h @@ -52,6 +52,18 @@ enum ucount_type { UCOUNT_COUNTS, }; +#if IS_ENABLED(CONFIG_BINFMT_MISC) +struct binfmt_namespace { + struct list_head entries; + rwlock_t entries_lock; + int enabled; + struct vfsmount *bm_mnt; + int entry_count; +} __randomize_layout; + +extern struct binfmt_namespace init_binfmt_ns; +#endif + struct user_namespace { struct uid_gid_map uid_map; struct uid_gid_map gid_map; @@ -86,6 +98,9 @@ struct user_namespace { #endif struct ucounts *ucounts; int ucount_max[UCOUNT_COUNTS]; +#if IS_ENABLED(CONFIG_BINFMT_MISC) + struct binfmt_namespace *binfmt_ns; +#endif } __randomize_layout; struct ucounts { diff --git a/kernel/user.c b/kernel/user.c index 5235d7f49982..092b2b4d47a6 100644 --- a/kernel/user.c +++ b/kernel/user.c @@ -20,6 +20,17 @@ #include #include +#if IS_ENABLED(CONFIG_BINFMT_MISC) +struct binfmt_namespace init_binfmt_ns = { + .entries = LIST_HEAD_INIT(init_binfmt_ns.entries), + .enabled = 1, + .entries_lock = __RW_LOCK_UNLOCKED(init_binfmt_ns.entries_lock), + .bm_mnt = NULL, + .entry_count = 0, +}; +EXPORT_SYMBOL_GPL(init_binfmt_ns); +#endif + /* * userns count is 1 for root user, 1 for init_uts_ns, * and 1 for... ? @@ -67,6 +78,9 @@ struct user_namespace init_user_ns = { .keyring_name_list = LIST_HEAD_INIT(init_user_ns.keyring_name_list), .keyring_sem = __RWSEM_INITIALIZER(init_user_ns.keyring_sem), #endif +#if IS_ENABLED(CONFIG_BINFMT_MISC) + .binfmt_ns = &init_binfmt_ns, +#endif }; EXPORT_SYMBOL_GPL(init_user_ns); diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 8eadadc478f9..f42c32269e20 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -191,6 +191,9 @@ static void free_user_ns(struct work_struct *work) kfree(ns->projid_map.forward); kfree(ns->projid_map.reverse); } +#if IS_ENABLED(CONFIG_BINFMT_MISC) + kfree(ns->binfmt_ns); +#endif retire_userns_sysctls(ns); key_free_user_ns(ns); ns_free_inum(&ns->ns);