[PATCH 4.11 43/84] NFSv4.1: Fix a race in nfs4_proc_layoutget

Greg Kroah-Hartman
2017-07-03T13:48:15Z

From: Trond Myklebust <trond.myklebust@primarydata.com>

commit bd171930e6a3de4f5cffdafbb944e50093dfb59b upstream.

If the task calling layoutget is signalled, then it is possible for the
calls to nfs4_sequence_free_slot() and nfs4_layoutget_prepare() to race,
in which case we leak a slot.
The fix is to move the call to nfs4_sequence_free_slot() into the
nfs4_layoutget_release() so that it gets called at task teardown time.

Fixes: 2e80dbe7ac51 ("NFSv4.1: Close callback races for OPEN, LAYOUTGET...")
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/nfs/nfs4proc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -8430,6 +8430,7 @@ static void nfs4_layoutget_release(void
size_t max_pages = max_response_pages(server);

dprintk("--> %s\n", __func__);
+ nfs4_sequence_free_slot(&lgp->res.seq_res);
nfs4_free_pages(lgp->args.layout.pages, max_pages);
pnfs_put_layout_hdr(NFS_I(inode)->layout);
put_nfs_open_context(lgp->args.ctx);
@@ -8504,7 +8505,6 @@ nfs4_proc_layoutget(struct nfs4_layoutge
/* if layoutp->len is 0, nfs4_layoutget_prepare called rpc_exit */
if (status == 0 && lgp->res.layoutp->len)
lseg = pnfs_layout_process(lgp);
- nfs4_sequence_free_slot(&lgp->res.seq_res);
rpc_put_task(task);
dprintk("<-- %s status=%d\n", __func__, status);
if (status)