From 2f62b5aa4814be2c511553fd6afb4d35b6c2503b Mon Sep 17 00:00:00 2001 From: Elena Reshetova Date: Fri, 20 Oct 2017 12:53:37 +0300 Subject: fs, nfs: convert nfs_lock_context.count from atomic_t to refcount_t atomic_t variables are currently used to implement reference counters with the following properties: - counter is initialized to 1 using atomic_set() - a resource is freed upon counter reaching zero - once counter reaches zero, its further increments aren't allowed - counter schema uses basic atomic operations (set, inc, inc_not_zero, dec_and_test, etc.) Such atomic variables should be converted to a newly provided refcount_t type and API that prevents accidental counter overflows and underflows. This is important since overflows and underflows can lead to use-after-free situation and be exploitable. The variable nfs_lock_context.count is used as pure reference counter. Convert it to refcount_t and fix up the operations. Suggested-by: Kees Cook Reviewed-by: David Windsor Reviewed-by: Hans Liljestrand Signed-off-by: Elena Reshetova Signed-off-by: Anna Schumaker --- include/linux/nfs_fs.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'include/linux/nfs_fs.h') diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h index 453f491a5fda..e6706913e6c2 100644 --- a/include/linux/nfs_fs.h +++ b/include/linux/nfs_fs.h @@ -22,6 +22,7 @@ #include #include #include +#include #include #include @@ -55,7 +56,7 @@ struct nfs_access_entry { }; struct nfs_lock_context { - atomic_t count; + refcount_t count; struct list_head list; struct nfs_open_context *open_context; fl_owner_t lockowner; -- cgit v1.2.3