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Message-Id: <1487585948-6401-3-git-send-email-elena.reshetova@intel.com>
Date: Mon, 20 Feb 2017 12:18:51 +0200
From: Elena Reshetova <elena.reshetova@...el.com>
To: linux-kernel@...r.kernel.org
Cc: cgroups@...r.kernel.org, linux-audit@...hat.com,
linux-fsdevel@...r.kernel.org, peterz@...radead.org,
gregkh@...uxfoundation.org, viro@...iv.linux.org.uk, tj@...nel.org,
mingo@...hat.com, hannes@...xchg.org, lizefan@...wei.com,
acme@...nel.org, alexander.shishkin@...ux.intel.com,
paul@...l-moore.com, eparis@...hat.com, akpm@...ux-foundation.org,
arnd@...db.de, luto@...nel.org,
Elena Reshetova <elena.reshetova@...el.com>,
Hans Liljestrand <ishkamiel@...il.com>,
Kees Cook <keescook@...omium.org>,
David Windsor <dwindsor@...il.com>
Subject: [PATCH 02/19] kernel: convert signal_struct.sigcnt from atomic_t to refcount_t
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 <elena.reshetova@...el.com>
Signed-off-by: Hans Liljestrand <ishkamiel@...il.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
Signed-off-by: David Windsor <dwindsor@...il.com>
---
include/linux/sched.h | 2 +-
kernel/fork.c | 6 +++---
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index a0430aa..6aad885 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -659,7 +659,7 @@ struct autogroup;
* the locking of signal_struct.
*/
struct signal_struct {
- atomic_t sigcnt;
+ refcount_t sigcnt;
atomic_t live;
int nr_threads;
struct list_head thread_head;
diff --git a/kernel/fork.c b/kernel/fork.c
index 9488f01..b432d1c 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -376,7 +376,7 @@ static inline void free_signal_struct(struct signal_struct *sig)
static inline void put_signal_struct(struct signal_struct *sig)
{
- if (atomic_dec_and_test(&sig->sigcnt))
+ if (refcount_dec_and_test(&sig->sigcnt))
free_signal_struct(sig);
}
@@ -1347,7 +1347,7 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
sig->nr_threads = 1;
atomic_set(&sig->live, 1);
- atomic_set(&sig->sigcnt, 1);
+ refcount_set(&sig->sigcnt, 1);
/* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
@@ -1826,7 +1826,7 @@ static __latent_entropy struct task_struct *copy_process(
} else {
current->signal->nr_threads++;
atomic_inc(¤t->signal->live);
- atomic_inc(¤t->signal->sigcnt);
+ refcount_inc(¤t->signal->sigcnt);
list_add_tail_rcu(&p->thread_group,
&p->group_leader->thread_group);
list_add_tail_rcu(&p->thread_node,
--
2.7.4
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