nfsd: fix use-after-free in nfsd_file_do_acquire tracepoint

[ Upstream commit bdd6b5624c62d0acd350d07564f1c82fe649235f ]

When we fail to insert into the hashtable with a non-retryable error,
we'll free the object and then goto out_status. If the tracepoint is
enabled, it'll end up accessing the freed object when it tries to
grab the fields out of it.

Set nf to NULL after freeing it to avoid the issue.

Fixes: 243a5263014a ("nfsd: rework hashtable handling in nfsd_do_file_acquire")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index 024adcbe67e95c1f20a06053cabd9894ceb85c85..dceb522f5cee95381a832cc6e92ccfb68493392b 100644 (file)
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -1075,6 +1075,7 @@ retry:
                goto open_file;
 
        nfsd_file_slab_free(&nf->nf_rcu);
+       nf = NULL;
        if (ret == -EEXIST)
                goto retry;
        trace_nfsd_file_insert_err(rqstp, key.inode, may_flags, ret);