[PATCH 5.19 555/717] NFSD: fix use-after-free on source server when doing inter-server copy

Greg Kroah-Hartman
2022-10-22T08:33:50Z

From: Dai Ngo <dai.ngo@oracle.com>

[ Upstream commit 019805fea91599b22dfa62ffb29c022f35abeb06 ]

Use-after-free occurred when the laundromat tried to free expired
cpntf_state entry on the s2s_cp_stateids list after inter-server
copy completed. The sc_cp_list that the expired copy state was
inserted on was already freed.

When COPY completes, the Linux client normally sends LOCKU(lock_state x),
FREE_STATEID(lock_state x) and CLOSE(open_state y) to the source server.
The nfs4_put_stid call from nfsd4_free_stateid cleans up the copy state
from the s2s_cp_stateids list before freeing the lock state's stid.

However, sometimes the CLOSE was sent before the FREE_STATEID request.
When this happens, the nfsd4_close_open_stateid call from nfsd4_close
frees all lock states on its st_locks list without cleaning up the copy
state on the sc_cp_list list. When the time the FREE_STATEID arrives the
server returns BAD_STATEID since the lock state was freed. This causes
the use-after-free error to occur when the laundromat tries to free
the expired cpntf_state.

This patch adds a call to nfs4_free_cpntf_statelist in
nfsd4_close_open_stateid to clean up the copy state before calling
free_ol_stateid_reaplist to free the lock state's stid on the reaplist.

Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/nfsd/nfs4state.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 9409a0dc1b76..c16646f9db31 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1049,6 +1049,7 @@ static struct nfs4_ol_stateid * nfs4_alloc_open_stateid(struct nfs4_client *clp)

static void nfs4_free_deleg(struct nfs4_stid *stid)
{
+ WARN_ON(!list_empty(&stid->sc_cp_list));
kmem_cache_free(deleg_slab, stid);
atomic_long_dec(&num_delegations);
}
@@ -1463,6 +1464,7 @@ static void nfs4_free_ol_stateid(struct nfs4_stid *stid)
release_all_access(stp);
if (stp->st_stateowner)
nfs4_put_stateowner(stp->st_stateowner);
+ WARN_ON(!list_empty(&stid->sc_cp_list));
kmem_cache_free(stateid_slab, stid);
}

@@ -6608,6 +6610,7 @@ static void nfsd4_close_open_stateid(struct nfs4_ol_stateid *s)
struct nfs4_client *clp = s->st_stid.sc_client;
bool unhashed;
LIST_HEAD(reaplist);
+ struct nfs4_ol_stateid *stp;

spin_lock(&clp->cl_lock);
unhashed = unhash_open_stateid(s, &reaplist);
@@ -6616,6 +6619,8 @@ static void nfsd4_close_open_stateid(struct nfs4_ol_stateid *s)
if (unhashed)
put_ol_stateid_locked(s, &reaplist);
spin_unlock(&clp->cl_lock);
+ list_for_each_entry(stp, &reaplist, st_locks)
+ nfs4_free_cpntf_statelist(clp->net, &stp->st_stid);
free_ol_stateid_reaplist(&reaplist);
} else {
spin_unlock(&clp->cl_lock);
--
2.35.1