NFS/localio: fix ref leak on nfs_uuid_add_file failure

When nfs_uuid_add_file() races with nfs_uuid_put() tearing down
uuid->net, it returns -ENXIO without publishing nfl->nfs_uuid via
rcu_assign_pointer().  nfs_open_local_fh() then enters its error
branch and only releases the slot's file ref and its paired net
ref plus its own entry-time net ref, while the close path is a
no-op:

    nfs_close_local_fh()
      nfs_uuid = rcu_dereference(nfl->nfs_uuid);
      if (!nfs_uuid) { rcu_read_unlock(); return; }  /* always */

nfsd_open_local_fh() returns localio holding a caller-owned +1
nfsd_file reference (from nfsd_file_get() after
nfsd_file_acquire_local()) and an entry-time nfsd_net reference
(from its first nfsd_net_try_get()) embedded as nf->nf_net.  Both
are leaked on the failure path, pinning one nfsd_file (and the
underlying struct file, dentry, inode) and one nfsd_net_ref per
occurrence, which blocks nfsd_net and netns teardown.

Fix by releasing the caller-owned file ref and its net ref through
the existing helper, using a stack-local RCU pointer so the helper
can xchg it out, then returning -ENXIO so callers do not
dereference a localio whose slot has been cleared:

    struct nfsd_file __rcu *tmp = RCU_INITIALIZER(localio);

    nfs_to_nfsd_file_put_local(pnf);
    nfs_to_nfsd_file_put_local(&tmp);
    localio = ERR_PTR(-ENXIO);

The trailing nfs_to_nfsd_net_put(net) continues to release the
outer net ref, so all three nfsd_net_try_get() increments are
balanced on the error branch.

Fixes: fdd015de7679 ("NFS/localio: nfs_uuid_put() fix races with nfs_open/close_local_fh()")
Cc: stable@vger.kernel.org
Assisted-by: kres:claude-opus-4-7
Signed-off-by: Chris Mason <clm@meta.com>
Link: https://patch.msgid.link/20260602-nfsd-testing-v2-3-e4ea62e3cd5c@kernel.org
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

0 files changed, 0 insertions, 0 deletions