From cff7cb2ece397760195ff8a5fc6bf3c860810246 Mon Sep 17 00:00:00 2001 From: Elena Reshetova Date: Fri, 20 Oct 2017 12:53:29 +0300 Subject: fs, nfsd: convert nfs4_cntl_odstate.co_odcount 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_cntl_odstate.co_odcount 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/nfs4state.c | 6 +++--- fs/nfsd/state.h | 2 +- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index df2e5b4..3f10a39 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -568,7 +568,7 @@ alloc_clnt_odstate(struct nfs4_client *clp) co = kmem_cache_zalloc(odstate_slab, GFP_KERNEL); if (co) { co->co_client = clp; - atomic_set(&co->co_odcount, 1); + refcount_set(&co->co_odcount, 1); } return co; } @@ -586,7 +586,7 @@ static inline void get_clnt_odstate(struct nfs4_clnt_odstate *co) { if (co) - atomic_inc(&co->co_odcount); + refcount_inc(&co->co_odcount); } static void @@ -598,7 +598,7 @@ put_clnt_odstate(struct nfs4_clnt_odstate *co) return; fp = co->co_file; - if (atomic_dec_and_lock(&co->co_odcount, &fp->fi_lock)) { + if (refcount_dec_and_lock(&co->co_odcount, &fp->fi_lock)) { list_del(&co->co_perfile); spin_unlock(&fp->fi_lock); diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h index c259271..2ed368a9 100644 --- a/fs/nfsd/state.h +++ b/fs/nfsd/state.h @@ -468,7 +468,7 @@ struct nfs4_clnt_odstate { struct nfs4_client *co_client; struct nfs4_file *co_file; struct list_head co_perfile; - atomic_t co_odcount; + refcount_t co_odcount; }; /* -- cgit v1.1