net, sunrpc: convert gss_cl_ctx.count from atomic_t to refcount_t

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 <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/sunrpc/auth_gss.h b/include/linux/sunrpc/auth_gss.h
index 36eebc4..cebdf87 100644 (file)
--- a/include/linux/sunrpc/auth_gss.h
+++ b/include/linux/sunrpc/auth_gss.h
@@ -13,6 +13,7 @@
 #define _LINUX_SUNRPC_AUTH_GSS_H
 
 #ifdef __KERNEL__
+#include <linux/refcount.h>
 #include <linux/sunrpc/auth.h>
 #include <linux/sunrpc/svc.h>
 #include <linux/sunrpc/gss_api.h>
@@ -65,7 +66,7 @@ struct rpc_gss_init_res {
  * the wire when communicating with a server. */
 
 struct gss_cl_ctx {
-       atomic_t                count;
+       refcount_t              count;
        enum rpc_gss_proc       gc_proc;
        u32                     gc_seq;
        spinlock_t              gc_seq_lock;

diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
index 4f16953..72f129c 100644 (file)
--- a/net/sunrpc/auth_gss/auth_gss.c
+++ b/net/sunrpc/auth_gss/auth_gss.c
@@ -117,14 +117,14 @@ static const struct rpc_pipe_ops gss_upcall_ops_v1;
 static inline struct gss_cl_ctx *
 gss_get_ctx(struct gss_cl_ctx *ctx)
 {
-       atomic_inc(&ctx->count);
+       refcount_inc(&ctx->count);
        return ctx;
 }
 
 static inline void
 gss_put_ctx(struct gss_cl_ctx *ctx)
 {
-       if (atomic_dec_and_test(&ctx->count))
+       if (refcount_dec_and_test(&ctx->count))
                gss_free_ctx(ctx);
 }
 
@@ -200,7 +200,7 @@ gss_alloc_context(void)
                ctx->gc_proc = RPC_GSS_PROC_DATA;
                ctx->gc_seq = 1;        /* NetApp 6.4R1 doesn't accept seq. no. 0 */
                spin_lock_init(&ctx->gc_seq_lock);
-               atomic_set(&ctx->count,1);
+               refcount_set(&ctx->count,1);
        }
        return ctx;
 }