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 --- fs/nfs/nfs4state.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'fs/nfs/nfs4state.c') diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c index 1887134d5231..3bd79b8c016b 100644 --- a/fs/nfs/nfs4state.c +++ b/fs/nfs/nfs4state.c @@ -1177,7 +1177,7 @@ void nfs4_schedule_state_manager(struct nfs_client *clp) if (test_and_set_bit(NFS4CLNT_MANAGER_RUNNING, &clp->cl_state) != 0) return; __module_get(THIS_MODULE); - atomic_inc(&clp->cl_count); + refcount_inc(&clp->cl_count); /* The rcu_read_lock() is not strictly necessary, as the state * manager is the only thread that ever changes the rpc_xprt @@ -1269,7 +1269,7 @@ int nfs4_wait_clnt_recover(struct nfs_client *clp) might_sleep(); - atomic_inc(&clp->cl_count); + refcount_inc(&clp->cl_count); res = wait_on_bit_action(&clp->cl_state, NFS4CLNT_MANAGER_RUNNING, nfs_wait_bit_killable, TASK_KILLABLE); if (res) @@ -2510,7 +2510,7 @@ static void nfs4_state_manager(struct nfs_client *clp) break; if (test_and_set_bit(NFS4CLNT_MANAGER_RUNNING, &clp->cl_state) != 0) break; - } while (atomic_read(&clp->cl_count) > 1); + } while (refcount_read(&clp->cl_count) > 1); return; out_error: if (strlen(section)) -- cgit v1.2.3-58-ga151