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Groups > linux.kernel > #1688905

[PATCH 10/15] kernel: convert nsproxy.count from atomic_t to refcount_t

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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/nsproxy.h | 6 +++---
 kernel/nsproxy.c        | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
index ac0d65b..f862ba8 100644
--- a/include/linux/nsproxy.h
+++ b/include/linux/nsproxy.h
@@ -28,7 +28,7 @@ struct fs_struct;
  * nsproxy is copied.
  */
 struct nsproxy {
-	atomic_t count;
+	refcount_t count;
 	struct uts_namespace *uts_ns;
 	struct ipc_namespace *ipc_ns;
 	struct mnt_namespace *mnt_ns;
@@ -74,14 +74,14 @@ int __init nsproxy_cache_init(void);
 
 static inline void put_nsproxy(struct nsproxy *ns)
 {
-	if (atomic_dec_and_test(&ns->count)) {
+	if (refcount_dec_and_test(&ns->count)) {
 		free_nsproxy(ns);
 	}
 }
 
 static inline void get_nsproxy(struct nsproxy *ns)
 {
-	atomic_inc(&ns->count);
+	refcount_inc(&ns->count);
 }
 
 #endif
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index f6c5d33..5bfe691 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -31,7 +31,7 @@
 static struct kmem_cache *nsproxy_cachep;
 
 struct nsproxy init_nsproxy = {
-	.count			= ATOMIC_INIT(1),
+	.count			= REFCOUNT_INIT(1),
 	.uts_ns			= &init_uts_ns,
 #if defined(CONFIG_POSIX_MQUEUE) || defined(CONFIG_SYSVIPC)
 	.ipc_ns			= &init_ipc_ns,
@@ -52,7 +52,7 @@ static inline struct nsproxy *create_nsproxy(void)
 
 	nsproxy = kmem_cache_alloc(nsproxy_cachep, GFP_KERNEL);
 	if (nsproxy)
-		atomic_set(&nsproxy->count, 1);
+		refcount_set(&nsproxy->count, 1);
 	return nsproxy;
 }
 
@@ -225,7 +225,7 @@ void switch_task_namespaces(struct task_struct *p, struct nsproxy *new)
 	p->nsproxy = new;
 	task_unlock(p);
 
-	if (ns && atomic_dec_and_test(&ns->count))
+	if (ns && refcount_dec_and_test(&ns->count))
 		free_nsproxy(ns);
 }
 
-- 
2.7.4

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[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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