From 2b28a7bee4539d27f4ec3b0298f03bfd83d4f794 Mon Sep 17 00:00:00 2001 From: Elena Reshetova Date: Fri, 20 Oct 2017 12:53:33 +0300 Subject: fs, nfs: convert pnfs_layout_hdr.plh_refcount 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 pnfs_layout_hdr.plh_refcount 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 --- fs/nfs/pnfs.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/nfs/pnfs.h') diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h index f0e98e1f04b2..78de7a2052f7 100644 --- a/fs/nfs/pnfs.h +++ b/fs/nfs/pnfs.h @@ -180,7 +180,7 @@ struct pnfs_layoutdriver_type { }; struct pnfs_layout_hdr { - atomic_t plh_refcount; + refcount_t plh_refcount; atomic_t plh_outstanding; /* number of RPCs out */ struct list_head plh_layouts; /* other client layouts */ struct list_head plh_bulk_destroy; -- cgit