From 81a090b9975b89ca15e71d0bca945358f6fe7696 Mon Sep 17 00:00:00 2001 From: Elena Reshetova Date: Fri, 20 Oct 2017 12:53:34 +0300 Subject: fs, nfs: convert nfs4_ff_layout_mirror.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_ff_layout_mirror.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: Anna Schumaker --- fs/nfs/flexfilelayout/flexfilelayout.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'fs/nfs/flexfilelayout/flexfilelayout.h') diff --git a/fs/nfs/flexfilelayout/flexfilelayout.h b/fs/nfs/flexfilelayout/flexfilelayout.h index 98b34c9b0564..ca35426ac3b4 100644 --- a/fs/nfs/flexfilelayout/flexfilelayout.h +++ b/fs/nfs/flexfilelayout/flexfilelayout.h @@ -13,6 +13,7 @@ #define FF_FLAGS_NO_IO_THRU_MDS 2 #define FF_FLAGS_NO_READ_IO 4 +#include #include "../pnfs.h" /* XXX: Let's filter out insanely large mirror count for now to avoid oom @@ -81,7 +82,7 @@ struct nfs4_ff_layout_mirror { nfs4_stateid stateid; struct rpc_cred __rcu *ro_cred; struct rpc_cred __rcu *rw_cred; - atomic_t ref; + refcount_t ref; spinlock_t lock; unsigned long flags; struct nfs4_ff_layoutstat read_stat; -- cgit v1.2.3-59-g8ed1b