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

[Elena Reshetova]

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 
Reviewed-by: David Windsor 
Reviewed-by: Hans Liljestrand 
Signed-off-by: Elena Reshetova 
---
 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 
 #include 
 #include 
+#include 
 #include 
 #include 
 #include 
@@ -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_tstack_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(>stack_refcount) ?
+   return refcount_inc_not_zero(>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(>stack_refcount))
+   if (refcount_dec_and_test(>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(>stack_refcount) != 0);
+   WARN_ON_ONCE(refcount_read(>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(>stack_refcount, 1);
+   refcount_set(>stack_refcount, 1);
 #endif
 
if (err)
-- 
2.7.4

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

[Elena Reshetova]

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 
Reviewed-by: David Windsor 
Reviewed-by: Hans Liljestrand 
Signed-off-by: Elena Reshetova 
---
 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 
 #include 
 #include 
+#include 
 #include 
 #include 
 #include 
@@ -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_tstack_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(>stack_refcount) ?
+   return refcount_inc_not_zero(>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(>stack_refcount))
+   if (refcount_dec_and_test(>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(>stack_refcount) != 0);
+   WARN_ON_ONCE(refcount_read(>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(>stack_refcount, 1);
+   refcount_set(>stack_refcount, 1);
 #endif
 
if (err)
-- 
2.7.4

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

[Elena Reshetova]

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/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 348466a..96802198 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -12,6 +12,7 @@
 #include 
 #include 
 #include 
+#include 
 #include 
 #include 
 #include 
@@ -208,7 +209,7 @@ 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 6a01517..73be022 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1070,7 +1070,7 @@ struct task_struct {
 #endif
 #ifdef CONFIG_THREAD_INFO_IN_TASK
/* A live task holds one reference: */
-   atomic_tstack_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(>stack_refcount) ?
+   return refcount_inc_not_zero(>stack_refcount) ?
task_stack_page(tsk) : NULL;
 }
 
diff --git a/kernel/fork.c b/kernel/fork.c
index c549b0b..1e0e14e 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(>stack_refcount))
+   if (refcount_dec_and_test(>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(>stack_refcount) != 0);
+   WARN_ON_ONCE(refcount_read(>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(>stack_refcount, 1);
+   refcount_set(>stack_refcount, 1);
 #endif
 
if (err)
-- 
2.7.4

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

[Elena Reshetova]

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/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 348466a..96802198 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -12,6 +12,7 @@
 #include 
 #include 
 #include 
+#include 
 #include 
 #include 
 #include 
@@ -208,7 +209,7 @@ 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 6a01517..73be022 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1070,7 +1070,7 @@ struct task_struct {
 #endif
 #ifdef CONFIG_THREAD_INFO_IN_TASK
/* A live task holds one reference: */
-   atomic_tstack_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(>stack_refcount) ?
+   return refcount_inc_not_zero(>stack_refcount) ?
task_stack_page(tsk) : NULL;
 }
 
diff --git a/kernel/fork.c b/kernel/fork.c
index c549b0b..1e0e14e 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(>stack_refcount))
+   if (refcount_dec_and_test(>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(>stack_refcount) != 0);
+   WARN_ON_ONCE(refcount_read(>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(>stack_refcount, 1);
+   refcount_set(>stack_refcount, 1);
 #endif
 
if (err)
-- 
2.7.4