From: Dave Wysochanski <dwysocha@redhat.com>
Date: Fri, 11 Dec 2020 05:12:51 -0500
Subject: [PATCH] NFS4: Fix use-after-free in
 trace_event_raw_event_nfs4_set_lock
Git-commit: 3d1a90ab0ed93362ec8ac85cf291243c87260c21
Patch-mainline: v5.11
References: git-fixes

It is only safe to call the tracepoint before rpc_put_task() because
'data' is freed inside nfs4_lock_release (rpc_release).

Fixes: 48c9579a1afe ("Adding stateid information to tracepoints")
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Acked-by: NeilBrown <neilb@suse.com>

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

--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -6431,9 +6431,9 @@ static int _nfs4_do_setlk(struct nfs4_st
 					data->arg.new_lock_owner, ret);
 	} else
 		data->cancelled = 1;
+	trace_nfs4_set_lock(fl, state, &data->res.stateid, cmd, ret);
 	rpc_put_task(task);
 	dprintk("%s: done, ret = %d!\n", __func__, ret);
-	trace_nfs4_set_lock(fl, state, &data->res.stateid, cmd, ret);
 	return ret;
 }