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[PATCH 05/15] kernel: convert task_struct.stack_refcount from atomic_t to refcount_t

From Elena Reshetova <elena.reshetova@intel.com>
Newsgroups linux.kernel
Subject [PATCH 05/15] kernel: convert task_struct.stack_refcount from atomic_t to refcount_t
Date 2017-07-17 12:50 +0200
Message-ID <u4bLf-3Tv-57@gated-at.bofh.it> (permalink)
References <u4bLb-3Tv-1@gated-at.bofh.it>
Organization linux.* mail to news gateway

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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.

Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
---
 include/linux/init_task.h        | 3 ++-
 include/linux/sched.h            | 2 +-
 include/linux/sched/task_stack.h | 2 +-
 kernel/fork.c                    | 6 +++---
 4 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 7ba3fca..8be9369 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -12,6 +12,7 @@
 #include <linux/securebits.h>
 #include <linux/seqlock.h>
 #include <linux/rbtree.h>
+#include <linux/refcount.h>
 #include <linux/sched/autogroup.h>
 #include <net/net_namespace.h>
 #include <linux/sched/rt.h>
@@ -214,7 +215,7 @@ extern struct cred init_cred;
 #ifdef CONFIG_THREAD_INFO_IN_TASK
 # define INIT_TASK_TI(tsk)			\
 	.thread_info = INIT_THREAD_INFO(tsk),	\
-	.stack_refcount = ATOMIC_INIT(1),
+	.stack_refcount = REFCOUNT_INIT(1),
 #else
 # define INIT_TASK_TI(tsk)
 #endif
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 9380e44..bd49917 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1078,7 +1078,7 @@ struct task_struct {
 #endif
 #ifdef CONFIG_THREAD_INFO_IN_TASK
 	/* A live task holds one reference: */
-	atomic_t			stack_refcount;
+	refcount_t			stack_refcount;
 #endif
 #ifdef CONFIG_LIVEPATCH
 	int patch_state;
diff --git a/include/linux/sched/task_stack.h b/include/linux/sched/task_stack.h
index df6ea66..aab3809 100644
--- a/include/linux/sched/task_stack.h
+++ b/include/linux/sched/task_stack.h
@@ -60,7 +60,7 @@ static inline unsigned long *end_of_stack(struct task_struct *p)
 #ifdef CONFIG_THREAD_INFO_IN_TASK
 static inline void *try_get_task_stack(struct task_struct *tsk)
 {
-	return atomic_inc_not_zero(&tsk->stack_refcount) ?
+	return refcount_inc_not_zero(&tsk->stack_refcount) ?
 		task_stack_page(tsk) : NULL;
 }
 
diff --git a/kernel/fork.c b/kernel/fork.c
index cfd8a42..6fd6be0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -354,7 +354,7 @@ static void release_task_stack(struct task_struct *tsk)
 #ifdef CONFIG_THREAD_INFO_IN_TASK
 void put_task_stack(struct task_struct *tsk)
 {
-	if (atomic_dec_and_test(&tsk->stack_refcount))
+	if (refcount_dec_and_test(&tsk->stack_refcount))
 		release_task_stack(tsk);
 }
 #endif
@@ -372,7 +372,7 @@ void free_task(struct task_struct *tsk)
 	 * If the task had a separate stack allocation, it should be gone
 	 * by now.
 	 */
-	WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0);
+	WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
 #endif
 	rt_mutex_debug_task_free(tsk);
 	ftrace_graph_exit_task(tsk);
@@ -532,7 +532,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 	tsk->stack_vm_area = stack_vm_area;
 #endif
 #ifdef CONFIG_THREAD_INFO_IN_TASK
-	atomic_set(&tsk->stack_refcount, 1);
+	refcount_set(&tsk->stack_refcount, 1);
 #endif
 
 	if (err)
-- 
2.7.4

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Thread

[PATCH 00/15] v3 kernel core pieces refcount conversions Elena Reshetova <elena.reshetova@intel.com> - 2017-07-17 12:50 +0200
  [PATCH 07/15] kernel: convert ring_buffer.refcount from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-07-17 12:50 +0200
  [PATCH 02/15] kernel: convert signal_struct.sigcnt from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-07-17 12:50 +0200
  [PATCH 04/15] kernel: convert task_struct.usage from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-07-17 12:50 +0200
  [PATCH 13/15] sched: convert numa_group.refcount from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-07-17 12:50 +0200
  [PATCH 03/15] kernel: convert user_struct.__count from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-07-17 12:50 +0200
  [PATCH 09/15] kernel: convert uprobe.ref from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-07-17 12:50 +0200
  [PATCH 14/15] kernel: convert futex_pi_state.refcount from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-07-17 12:50 +0200
    Re: [PATCH 14/15] kernel: convert futex_pi_state.refcount from  atomic_t to refcount_t Thomas Gleixner <tglx@linutronix.de> - 2017-07-17 16:30 +0200
      RE: [PATCH 14/15] kernel: convert futex_pi_state.refcount from  atomic_t to refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-07-17 19:00 +0200
        RE: [PATCH 14/15] kernel: convert futex_pi_state.refcount from  atomic_t to refcount_t Thomas Gleixner <tglx@linutronix.de> - 2017-07-17 20:00 +0200
          RE: [PATCH 14/15] kernel: convert futex_pi_state.refcount from  atomic_t to refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-07-18 11:40 +0200
  [PATCH 15/15] kernel: convert kcov.refcount from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-07-17 12:50 +0200
  [PATCH 10/15] kernel: convert nsproxy.count from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-07-17 12:50 +0200
  [PATCH 11/15] kernel: convert group_info.usage from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-07-17 12:50 +0200
  [PATCH 01/15] kernel: convert sighand_struct.count from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-07-17 12:50 +0200
  [PATCH 05/15] kernel: convert task_struct.stack_refcount from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-07-17 12:50 +0200
  [PATCH 06/15] kernel: convert perf_event_context.refcount from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-07-17 12:50 +0200
  [PATCH 12/15] kernel: convert cred.usage from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-07-17 12:50 +0200

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