[PATCH] NFSD: Fix potential use-after-free in nfsd_file_put()

[Chuck Lever <chuck.lever@xxxxxxxxxx>]

nfsd_file_put_noref() can free @nf, so don't dereference @nf
immediately upon return from nfsd_file_put_noref().

Suggested-by: Trond Myklebust <trondmy@xxxxxxxxxxxxxxx>
Fixes: 999397926ab3 ("nfsd: Clean up nfsd_file_put()")
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
 fs/nfsd/filecache.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index d32fcd8ad457..148b25a43caf 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -308,11 +308,12 @@ nfsd_file_put(struct nfsd_file *nf)
 	if (test_bit(NFSD_FILE_HASHED, &nf->nf_flags) == 0) {
 		nfsd_file_flush(nf);
 		nfsd_file_put_noref(nf);
-	} else {
+	} else if (nf->nf_file) {
 		nfsd_file_put_noref(nf);
-		if (nf->nf_file)
-			nfsd_file_schedule_laundrette();
-	}
+		nfsd_file_schedule_laundrette();
+	} else
+		nfsd_file_put_noref(nf);
+
 	if (atomic_long_read(&nfsd_filecache_count) >= NFSD_FILE_LRU_LIMIT)
 		nfsd_file_gc();
 }