seccomp: Switch from atomic_t to recount_t

This switches the seccomp usage tracking from atomic_t to refcount_t to
gain refcount overflow protections.

Cc: Elena Reshetova <elena.reshetova@intel.com>
Cc: David Windsor <dwindsor@gmail.com>
Cc: Hans Liljestrand <hans.liljestrand@aalto.fi>
Signed-off-by: Kees Cook <keescook@chromium.org>

1 files changed, 5 insertions, 5 deletions

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index fce83885b7ef..98b59b5db90b 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -13,7 +13,7 @@
  *        of Berkeley Packet Filters/Linux Socket Filters.
  */
 
-#include <linux/atomic.h>
+#include <linux/refcount.h>
 #include <linux/audit.h>
 #include <linux/compat.h>
 #include <linux/coredump.h>
@@ -56,7 +56,7 @@
  * to a task_struct (other than @usage).
  */
 struct seccomp_filter {
-        atomic_t usage;
+        refcount_t usage;
         struct seccomp_filter *prev;
         struct bpf_prog *prog;
 };
@@ -378,7 +378,7 @@ static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
                 return ERR_PTR(ret);
         }
 
-        atomic_set(&sfilter->usage, 1);
+        refcount_set(&sfilter->usage, 1);
 
         return sfilter;
 }
@@ -465,7 +465,7 @@ void get_seccomp_filter(struct task_struct *tsk)
         if (!orig)
                 return;
         /* Reference count is bounded by the number of total processes. */
-        atomic_inc(&orig->usage);
+        refcount_inc(&orig->usage);
 }
 
 static inline void seccomp_filter_free(struct seccomp_filter *filter)
@@ -481,7 +481,7 @@ void put_seccomp_filter(struct task_struct *tsk)
 {
         struct seccomp_filter *orig = tsk->seccomp.filter;
         /* Clean up single-reference branches iteratively. */
-        while (orig && atomic_dec_and_test(&orig->usage)) {
+        while (orig && refcount_dec_and_test(&orig->usage)) {
                 struct seccomp_filter *freeme = orig;
                 orig = orig->prev;
                 seccomp_filter_free(freeme);