| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <tip-ec1d281923cf81cc660343d0cb8ffc837ffb991d@git.kernel.org>
Date: Mon, 4 Feb 2019 00:55:42 -0800
From: tip-bot for Elena Reshetova <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: elena.reshetova@...el.com, linux-kernel@...r.kernel.org,
dwindsor@...il.com, ishkamiel@...il.com, peterz@...radead.org,
efault@....de, keescook@...omium.org,
torvalds@...ux-foundation.org, mingo@...nel.org, hpa@...or.com,
tglx@...utronix.de, andrea.parri@...rulasolutions.com
Subject: [tip:sched/core] sched/core: Convert task_struct.usage to
refcount_t
Commit-ID: ec1d281923cf81cc660343d0cb8ffc837ffb991d
Gitweb: https://git.kernel.org/tip/ec1d281923cf81cc660343d0cb8ffc837ffb991d
Author: Elena Reshetova <elena.reshetova@...el.com>
AuthorDate: Fri, 18 Jan 2019 14:27:29 +0200
Committer: Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 4 Feb 2019 08:53:55 +0100
sched/core: Convert task_struct.usage to refcount_t
atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.
The variable task_struct.usage is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
** Important note for maintainers:
Some functions from refcount_t API defined in lib/refcount.c
have different memory ordering guarantees than their atomic
counterparts.
The full comparison can be seen in
https://lkml.org/lkml/2017/11/15/57 and it is hopefully soon
in state to be merged to the documentation tree.
Normally the differences should not matter since refcount_t provides
enough guarantees to satisfy the refcounting use cases, but in
some rare cases it might matter.
Please double check that you don't have some undocumented
memory guarantees for this variable usage.
For the task_struct.usage it might make a difference
in following places:
- put_task_struct(): decrement in refcount_dec_and_test() only
provides RELEASE ordering and control dependency on success
vs. fully ordered atomic counterpart
Suggested-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Elena Reshetova <elena.reshetova@...el.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: David Windsor <dwindsor@...il.com>
Reviewed-by: Hans Liljestrand <ishkamiel@...il.com>
Reviewed-by: Andrea Parri <andrea.parri@...rulasolutions.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: akpm@...ux-foundation.org
Cc: viro@...iv.linux.org.uk
Link: https://lkml.kernel.org/r/1547814450-18902-5-git-send-email-elena.reshetova@intel.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
include/linux/sched.h | 3 ++-
include/linux/sched/task.h | 4 ++--
init/init_task.c | 2 +-
kernel/fork.c | 4 ++--
4 files changed, 7 insertions(+), 6 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index e2bba022827d..9d14d6864ca6 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -21,6 +21,7 @@
#include <linux/seccomp.h>
#include <linux/nodemask.h>
#include <linux/rcupdate.h>
+#include <linux/refcount.h>
#include <linux/resource.h>
#include <linux/latencytop.h>
#include <linux/sched/prio.h>
@@ -607,7 +608,7 @@ struct task_struct {
randomized_struct_fields_start
void *stack;
- atomic_t usage;
+ refcount_t usage;
/* Per task flags (PF_*), defined further below: */
unsigned int flags;
unsigned int ptrace;
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 44c6f15800ff..2e97a2227045 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -88,13 +88,13 @@ extern void sched_exec(void);
#define sched_exec() {}
#endif
-#define get_task_struct(tsk) do { atomic_inc(&(tsk)->usage); } while(0)
+#define get_task_struct(tsk) do { refcount_inc(&(tsk)->usage); } while(0)
extern void __put_task_struct(struct task_struct *t);
static inline void put_task_struct(struct task_struct *t)
{
- if (atomic_dec_and_test(&t->usage))
+ if (refcount_dec_and_test(&t->usage))
__put_task_struct(t);
}
diff --git a/init/init_task.c b/init/init_task.c
index 9aa3ebc74970..aca34c89529f 100644
--- a/init/init_task.c
+++ b/init/init_task.c
@@ -65,7 +65,7 @@ struct task_struct init_task
#endif
.state = 0,
.stack = init_stack,
- .usage = ATOMIC_INIT(2),
+ .usage = REFCOUNT_INIT(2),
.flags = PF_KTHREAD,
.prio = MAX_PRIO - 20,
.static_prio = MAX_PRIO - 20,
diff --git a/kernel/fork.c b/kernel/fork.c
index 935a42d5f8ff..3f7e192e29f2 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -717,7 +717,7 @@ static inline void put_signal_struct(struct signal_struct *sig)
void __put_task_struct(struct task_struct *tsk)
{
WARN_ON(!tsk->exit_state);
- WARN_ON(atomic_read(&tsk->usage));
+ WARN_ON(refcount_read(&tsk->usage));
WARN_ON(tsk == current);
cgroup_free(tsk);
@@ -896,7 +896,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
* One for us, one for whoever does the "release_task()" (usually
* parent)
*/
- atomic_set(&tsk->usage, 2);
+ refcount_set(&tsk->usage, 2);
#ifdef CONFIG_BLK_DEV_IO_TRACE
tsk->btrace_seq = 0;
#endif
Powered by blists - more mailing lists