From 212bf41d88c06afc23e03f9b274eebf1e8dba197 Mon Sep 17 00:00:00 2001 From: Elena Reshetova Date: Fri, 20 Oct 2017 12:53:38 +0300 Subject: fs, nfs: convert nfs_client.cl_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_client.cl_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_sb.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'include/linux/nfs_fs_sb.h') diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h index 74c44665e6d3..efcfe9ded9ea 100644 --- a/include/linux/nfs_fs_sb.h +++ b/include/linux/nfs_fs_sb.h @@ -9,6 +9,7 @@ #include #include +#include struct nfs4_session; struct nfs_iostats; @@ -24,7 +25,7 @@ struct nfs41_impl_id; * The nfs_client identifies our client state to the server. */ struct nfs_client { - atomic_t cl_count; + refcount_t cl_count; atomic_t cl_mds_count; int cl_cons_state; /* current construction state (-ve: init error) */ #define NFS_CS_READY 0 /* ready to be used */ -- cgit