Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752525AbdGGJKT (ORCPT ); Fri, 7 Jul 2017 05:10:19 -0400 Received: from mga07.intel.com ([134.134.136.100]:5732 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752554AbdGGJHB (ORCPT ); Fri, 7 Jul 2017 05:07:01 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.40,321,1496127600"; d="scan'208";a="284088447" From: Elena Reshetova To: linux-kernel@vger.kernel.org Cc: cgroups@vger.kernel.org, linux-audit@redhat.com, linux-fsdevel@vger.kernel.org, peterz@infradead.org, gregkh@linuxfoundation.org, viro@zeniv.linux.org.uk, tj@kernel.org, mingo@redhat.com, hannes@cmpxchg.org, lizefan@huawei.com, acme@kernel.org, alexander.shishkin@linux.intel.com, eparis@redhat.com, akpm@linux-foundation.org, arnd@arndb.de, luto@kernel.org, keescook@chromium.org, Elena Reshetova , Hans Liljestrand , David Windsor Subject: [PATCH 03/15] kernel: convert user_struct.__count from atomic_t to refcount_t Date: Fri, 7 Jul 2017 12:04:17 +0300 Message-Id: <1499418269-3686-4-git-send-email-elena.reshetova@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1499418269-3686-1-git-send-email-elena.reshetova@intel.com> References: <1499418269-3686-1-git-send-email-elena.reshetova@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2707 Lines: 87 refcount_t type and corresponding API should be used instead of atomic_t when the variable is used as a reference counter. This allows to avoid accidental refcounter overflows that might lead to use-after-free situations. Signed-off-by: Elena Reshetova Signed-off-by: Hans Liljestrand Signed-off-by: Kees Cook Signed-off-by: David Windsor --- include/linux/sched/user.h | 5 +++-- kernel/user.c | 8 ++++---- 2 files changed, 7 insertions(+), 6 deletions(-) diff --git a/include/linux/sched/user.h b/include/linux/sched/user.h index 5d5415e..0a9953d 100644 --- a/include/linux/sched/user.h +++ b/include/linux/sched/user.h @@ -3,6 +3,7 @@ #include #include +#include struct key; @@ -10,7 +11,7 @@ struct key; * Some day this will be a full-fledged user tracking system.. */ struct user_struct { - atomic_t __count; /* reference count */ + refcount_t __count; /* reference count */ atomic_t processes; /* How many processes does this user have? */ atomic_t sigpending; /* How many pending signals does this user have? */ #ifdef CONFIG_FANOTIFY @@ -53,7 +54,7 @@ extern struct user_struct root_user; extern struct user_struct * alloc_uid(kuid_t); static inline struct user_struct *get_uid(struct user_struct *u) { - atomic_inc(&u->__count); + refcount_inc(&u->__count); return u; } extern void free_uid(struct user_struct *); diff --git a/kernel/user.c b/kernel/user.c index 00281ad..c072348 100644 --- a/kernel/user.c +++ b/kernel/user.c @@ -90,7 +90,7 @@ static DEFINE_SPINLOCK(uidhash_lock); /* root_user.__count is 1, for init task cred */ struct user_struct root_user = { - .__count = ATOMIC_INIT(1), + .__count = REFCOUNT_INIT(1), .processes = ATOMIC_INIT(1), .sigpending = ATOMIC_INIT(0), .locked_shm = 0, @@ -116,7 +116,7 @@ static struct user_struct *uid_hash_find(kuid_t uid, struct hlist_head *hashent) hlist_for_each_entry(user, hashent, uidhash_node) { if (uid_eq(user->uid, uid)) { - atomic_inc(&user->__count); + refcount_inc(&user->__count); return user; } } @@ -163,7 +163,7 @@ void free_uid(struct user_struct *up) return; local_irq_save(flags); - if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) + if (refcount_dec_and_lock(&up->__count, &uidhash_lock)) free_user(up, flags); else local_irq_restore(flags); @@ -184,7 +184,7 @@ struct user_struct *alloc_uid(kuid_t uid) goto out_unlock; new->uid = uid; - atomic_set(&new->__count, 1); + refcount_set(&new->__count, 1); /* * Before adding this, check whether we raced -- 2.7.4