From 818a34eb266449b1c89242596039a5e44c9be04c Mon Sep 17 00:00:00 2001 From: Elena Reshetova Date: Fri, 20 Oct 2017 12:53:30 +0300 Subject: fs, nfsd: convert nfs4_file.fi_ref 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_file.fi_ref 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/state.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'fs/nfsd/state.h') diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h index 2ed368a91a10..f3772ea8ba0d 100644 --- a/fs/nfsd/state.h +++ b/fs/nfsd/state.h @@ -484,7 +484,7 @@ struct nfs4_clnt_odstate { * the global state_lock spinlock. */ struct nfs4_file { - atomic_t fi_ref; + refcount_t fi_ref; spinlock_t fi_lock; struct hlist_node fi_hash; /* hash on fi_fhandle */ struct list_head fi_stateids; @@ -637,7 +637,7 @@ struct nfs4_file *find_file(struct knfsd_fh *fh); void put_nfs4_file(struct nfs4_file *fi); static inline void get_nfs4_file(struct nfs4_file *fi) { - atomic_inc(&fi->fi_ref); + refcount_inc(&fi->fi_ref); } struct file *find_any_file(struct nfs4_file *f); -- cgit v1.2.3