From a15dfcd529ab43265e70ec32d3b9d2286872d412 Mon Sep 17 00:00:00 2001 From: Elena Reshetova Date: Fri, 20 Oct 2017 12:53:28 +0300 Subject: fs, nfsd: convert nfs4_stid.sc_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 nfs4_stid.sc_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: J. Bruce Fields --- fs/nfsd/nfs4layouts.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'fs/nfsd/nfs4layouts.c') diff --git a/fs/nfsd/nfs4layouts.c b/fs/nfsd/nfs4layouts.c index e122da696f1b..fed076069dd2 100644 --- a/fs/nfsd/nfs4layouts.c +++ b/fs/nfsd/nfs4layouts.c @@ -335,7 +335,7 @@ nfsd4_recall_file_layout(struct nfs4_layout_stateid *ls) trace_layout_recall(&ls->ls_stid.sc_stateid); - atomic_inc(&ls->ls_stid.sc_count); + refcount_inc(&ls->ls_stid.sc_count); nfsd4_run_cb(&ls->ls_recall); out_unlock: @@ -440,7 +440,7 @@ nfsd4_insert_layout(struct nfsd4_layoutget *lgp, struct nfs4_layout_stateid *ls) goto done; } - atomic_inc(&ls->ls_stid.sc_count); + refcount_inc(&ls->ls_stid.sc_count); list_add_tail(&new->lo_perstate, &ls->ls_layouts); new = NULL; done: -- cgit v1.2.3