From patchwork Mon Feb 1 14:18:30 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexey Gladkov X-Patchwork-Id: 12059117 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.7 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4696BC433DB for ; Mon, 1 Feb 2021 14:21:39 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 173EB64DCC for ; Mon, 1 Feb 2021 14:21:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 173EB64DCC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-20705-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 26252 invoked by uid 550); 1 Feb 2021 14:21:13 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 26136 invoked from network); 1 Feb 2021 14:21:12 -0000 From: Alexey Gladkov To: LKML , io-uring@vger.kernel.org, Kernel Hardening , Linux Containers , linux-mm@kvack.org Cc: Alexey Gladkov , Andrew Morton , Christian Brauner , "Eric W . Biederman" , Jann Horn , Jens Axboe , Kees Cook , Linus Torvalds , Oleg Nesterov Subject: [PATCH v5 2/7] Add a reference to ucounts for each cred Date: Mon, 1 Feb 2021 15:18:30 +0100 Message-Id: <9ac6beb4b568cb980635b2c38e90839e0deace85.1612188590.git.gladkov.alexey@gmail.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: References: MIME-Version: 1.0 X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.6.1 (raptor.unsafe.ru [5.9.43.93]); Mon, 01 Feb 2021 14:21:01 +0000 (UTC) For RLIMIT_NPROC and some other rlimits the user_struct that holds the global limit is kept alive for the lifetime of a process by keeping it in struct cred. Adding a pointer to ucounts in the struct cred will allow to track RLIMIT_NPROC not only for user in the system, but for user in the user_namespace. Updating ucounts may require memory allocation which may fail. So, we cannot change cred.ucounts in the commit_creds() because this function cannot fail and it should always return 0. For this reason, we modify cred.ucounts before calling the commit_creds(). Signed-off-by: Alexey Gladkov --- fs/exec.c | 4 +++ include/linux/cred.h | 2 ++ include/linux/user_namespace.h | 3 +++ kernel/cred.c | 45 ++++++++++++++++++++++++++++++++++ kernel/fork.c | 6 +++++ kernel/sys.c | 12 +++++++++ kernel/ucount.c | 26 +++++++++++++++++--- kernel/user_namespace.c | 3 +++ 8 files changed, 98 insertions(+), 3 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index 5d4d52039105..0371a3400be5 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1360,6 +1360,10 @@ int begin_new_exec(struct linux_binprm * bprm) WRITE_ONCE(me->self_exec_id, me->self_exec_id + 1); flush_signal_handlers(me, 0); + retval = set_cred_ucounts(bprm->cred); + if (retval < 0) + goto out_unlock; + /* * install the new credentials for this executable */ diff --git a/include/linux/cred.h b/include/linux/cred.h index 18639c069263..ad160e5fe5c6 100644 --- a/include/linux/cred.h +++ b/include/linux/cred.h @@ -144,6 +144,7 @@ struct cred { #endif struct user_struct *user; /* real user ID subscription */ struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */ + struct ucounts *ucounts; struct group_info *group_info; /* supplementary groups for euid/fsgid */ /* RCU deletion */ union { @@ -170,6 +171,7 @@ extern int set_security_override_from_ctx(struct cred *, const char *); extern int set_create_files_as(struct cred *, struct inode *); extern int cred_fscmp(const struct cred *, const struct cred *); extern void __init cred_init(void); +extern int set_cred_ucounts(struct cred *); /* * check for validity of credentials diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h index 0bb833fd41f4..43f5847cc897 100644 --- a/include/linux/user_namespace.h +++ b/include/linux/user_namespace.h @@ -102,6 +102,9 @@ bool setup_userns_sysctls(struct user_namespace *ns); void retire_userns_sysctls(struct user_namespace *ns); struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, enum ucount_type type); void dec_ucount(struct ucounts *ucounts, enum ucount_type type); +struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid); +struct ucounts *get_ucounts(struct ucounts *ucounts); +void put_ucounts(struct ucounts *ucounts); #ifdef CONFIG_USER_NS diff --git a/kernel/cred.c b/kernel/cred.c index 421b1149c651..8194a59e283f 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -119,6 +119,8 @@ static void put_cred_rcu(struct rcu_head *rcu) if (cred->group_info) put_group_info(cred->group_info); free_uid(cred->user); + if (cred->ucounts) + put_ucounts(cred->ucounts); put_user_ns(cred->user_ns); kmem_cache_free(cred_jar, cred); } @@ -284,6 +286,11 @@ struct cred *prepare_creds(void) if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) goto error; + + new->ucounts = get_ucounts(new->ucounts); + if (!new->ucounts) + goto error; + validate_creds(new); return new; @@ -363,6 +370,8 @@ int copy_creds(struct task_struct *p, unsigned long clone_flags) ret = create_user_ns(new); if (ret < 0) goto error_put; + if (set_cred_ucounts(new) < 0) + goto error_put; } #ifdef CONFIG_KEYS @@ -653,6 +662,33 @@ int cred_fscmp(const struct cred *a, const struct cred *b) } EXPORT_SYMBOL(cred_fscmp); +int set_cred_ucounts(struct cred *new) +{ + struct task_struct *task = current; + const struct cred *old = task->real_cred; + struct ucounts *old_ucounts = new->ucounts; + + BUG_ON(task->cred != old); + + if (new->user == old->user && new->user_ns == old->user_ns) + return 0; + + /* + * This optimization is needed because alloc_ucounts() uses locks + * for table lookups. + */ + if (old_ucounts && old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->euid)) + return 0; + + if (!(new->ucounts = alloc_ucounts(new->user_ns, new->euid))) + return -EAGAIN; + + if (old_ucounts) + put_ucounts(old_ucounts); + + return 0; +} + /* * initialise the credentials stuff */ @@ -661,6 +697,11 @@ void __init cred_init(void) /* allocate a slab in which we can store credentials */ cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL); + /* + * This is needed here because this is the first cred and there is no + * ucount reference to copy. + */ + init_cred.ucounts = alloc_ucounts(init_cred.user_ns, init_cred.euid); } /** @@ -719,6 +760,10 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon) if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) goto error; + new->ucounts = get_ucounts(new->ucounts); + if (!new->ucounts) + goto error; + put_cred(old); validate_creds(new); return new; diff --git a/kernel/fork.c b/kernel/fork.c index 37720a6d04ea..b0d36dea0a9c 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2959,6 +2959,12 @@ int ksys_unshare(unsigned long unshare_flags) if (err) goto bad_unshare_cleanup_cred; + if (new_cred) { + err = set_cred_ucounts(new_cred); + if (err) + goto bad_unshare_cleanup_cred; + } + if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { if (do_sysvsem) { /* diff --git a/kernel/sys.c b/kernel/sys.c index 51f00fe20e4d..373def7debe8 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -553,6 +553,10 @@ long __sys_setreuid(uid_t ruid, uid_t euid) if (retval < 0) goto error; + retval = set_cred_ucounts(new); + if (retval < 0) + goto error; + return commit_creds(new); error: @@ -611,6 +615,10 @@ long __sys_setuid(uid_t uid) if (retval < 0) goto error; + retval = set_cred_ucounts(new); + if (retval < 0) + goto error; + return commit_creds(new); error: @@ -686,6 +694,10 @@ long __sys_setresuid(uid_t ruid, uid_t euid, uid_t suid) if (retval < 0) goto error; + retval = set_cred_ucounts(new); + if (retval < 0) + goto error; + return commit_creds(new); error: diff --git a/kernel/ucount.c b/kernel/ucount.c index 04c561751af1..9644bced74b4 100644 --- a/kernel/ucount.c +++ b/kernel/ucount.c @@ -125,7 +125,7 @@ static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struc return NULL; } -static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) +struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid) { struct hlist_head *hashent = ucounts_hashentry(ns, uid); struct ucounts *ucounts, *new; @@ -160,11 +160,31 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) return ucounts; } -static void put_ucounts(struct ucounts *ucounts) +struct ucounts *get_ucounts(struct ucounts *ucounts) +{ + unsigned long flags; + + if (!ucounts) + return NULL; + + spin_lock_irqsave(&ucounts_lock, flags); + if (ucounts->count == INT_MAX) { + WARN_ONCE(1, "ucounts: counter has reached its maximum value"); + ucounts = NULL; + } else { + ucounts->count += 1; + } + spin_unlock_irqrestore(&ucounts_lock, flags); + + return ucounts; +} + +void put_ucounts(struct ucounts *ucounts) { unsigned long flags; spin_lock_irqsave(&ucounts_lock, flags); + BUG_ON(ucounts->count <= 0); ucounts->count -= 1; if (!ucounts->count) hlist_del_init(&ucounts->node); @@ -194,7 +214,7 @@ struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, { struct ucounts *ucounts, *iter, *bad; struct user_namespace *tns; - ucounts = get_ucounts(ns, uid); + ucounts = alloc_ucounts(ns, uid); for (iter = ucounts; iter; iter = tns->ucounts) { long max; tns = iter->ns; diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index af612945a4d0..516db53166ab 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -1281,6 +1281,9 @@ static int userns_install(struct nsset *nsset, struct ns_common *ns) put_user_ns(cred->user_ns); set_cred_user_ns(cred, get_user_ns(user_ns)); + if (set_cred_ucounts(cred) < 0) + return -EINVAL; + return 0; }