FAILED: patch "[PATCH] NFSD: Prevent client use-after-free during close_lru reaping" failed to apply to 6.18-stable tree

FAILED: patch "[PATCH] NFSD: Prevent client use-after-free during close_lru reaping" failed to apply to 6.18-stable tree

[gregkh]

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 2330b788d732f43668b965b3105b37ceb276dfea
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026090304-waking-garnish-23bc@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2330b788d732f43668b965b3105b37ceb276dfea Mon Sep 17 00:00:00 2001
From: Chuck Lever <cel@kernel.org>
Date: Thu, 9 Jul 2026 13:40:31 -0400
Subject: [PATCH] NFSD: Prevent client use-after-free during close_lru reaping

An nfs4_openowner left on nn->close_lru after its final CLOSE keeps
its last closed stateid in oo_last_closed_stid, holding only a raw
pointer to its nfs4_client. The laundromat reaps timed-out entries,
drops nn->client_lock, and calls nfs4_put_stid(), which dereferences
the client through cl_lock. Nothing pins the client across that
window, so a concurrent force_expire_client() can free it and
nfs4_put_stid() reads freed memory. __destroy_client() hits the same
race, walking clp->cl_openowners without cl_lock.

Pin the client with cl_rpc_users before dropping client_lock, and
skip clients already expiring. __destroy_client() then cleans up its
own close_lru entries through release_last_closed_stateid(), so
teardown no longer races the laundromat.

Fixes: 217526e7ecc9 ("nfsd: protect the close_lru list and oo_last_closed_stid with client_lock")
Cc: stable@vger.kernel.org
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260709-cel-v4-8-1d519d9be0cb@kernel.org
Signed-off-by: Chuck Lever <cel@kernel.org>

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 4acd02f1642c..20556b8f186a 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -7581,11 +7581,16 @@ nfs4_laundromat(struct nfsd_net *nn)
 		if (!state_expired(&lt, oo->oo_time))
 			break;
 		list_del_init(&oo->oo_close_lru);
+		clp = oo->oo_owner.so_client;
+		if (is_client_expired(clp))
+			continue;
 		stp = oo->oo_last_closed_stid;
 		oo->oo_last_closed_stid = NULL;
+		atomic_inc(&clp->cl_rpc_users);
 		spin_unlock(&nn->client_lock);
 		nfs4_put_stid(&stp->st_stid);
 		spin_lock(&nn->client_lock);
+		put_client_no_renew_locked(clp);
 	}
 	spin_unlock(&nn->client_lock);
 

[PATCH 6.18.y 1/4] NFSD: Prevent client use-after-free during delegation revoke

[Sasha Levin]

From: Chuck Lever <cel@kernel.org>

[ Upstream commit 4683ca76b3b7e5808338491c6eb3c20e6b4894d5 ]

A delegation stateid holds only a bare pointer to its owning
nfs4_client and does not keep it alive.  The client survives its
stateids only because __destroy_client() drains cl_delegations and
cl_revoked before free_client() runs.

nfs4_laundromat() breaks that invariant: it unhashes an
expired delegation from cl_delegations, drops deleg_lock, then
revoke_delegation() relinks it onto cl_revoked under cl_lock.  In that
window the delegation is on neither list, so client_has_state() can
report no remaining state.

Every teardown path first requires cl_rpc_users to be zero, but
the laundromat holds no such reference.  A client whose recalled
delegation has just timed out can therefore reach free_client()
while revoke_delegation() is still about to dereference cl_lock,
a use-after-free.

Pin the client with cl_rpc_users across the revoke so teardown blocks
until it completes, then reap the delegation from cl_revoked.  A client
already expiring reaps its own, so skip it and leave the delegation on
del_recall_lru.

Fixes: 3bd64a5ba171 ("nfsd4: implement SEQ4_STATUS_RECALLABLE_STATE_REVOKED")
Cc: stable@vger.kernel.org
Reviewed-by: NeilBrown <neil@brown.name>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260709-cel-v4-2-1d519d9be0cb@kernel.org
Signed-off-by: Chuck Lever <cel@kernel.org>

[ sashal: Reduced backport -- upstream 4683ca76b3b7e touches 2 file(s), this
  backport carries 1. Not backported here:
  fs/nfsd/netns.h
  This note is generated from the file lists only; see the resolution record
  for the reasoning. ]

Stable-dep-of: 2330b788d732 ("NFSD: Prevent client use-after-free during close_lru reaping")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/nfsd/nfs4state.c | 29 ++++++++++++++++++++++++++---
 1 file changed, 26 insertions(+), 3 deletions(-)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 48715a55df8fa..1453f4769ab98 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -92,9 +92,9 @@ static void deleg_reaper(struct nfsd_net *nn);
 /* Locking: */
 
 /*
- * Currently used for the del_recall_lru and file hash table.  In an
- * effort to decrease the scope of the client_mutex, this spinlock may
- * eventually cover more:
+ * Currently used for the del_recall_lru and file hash table.  It nests
+ * outside client_lock.  In an effort to decrease the scope of the
+ * client_mutex, this spinlock may eventually cover more:
  */
 static DEFINE_SPINLOCK(state_lock);
 
@@ -7052,6 +7052,7 @@ nfs4_laundromat(struct nfsd_net *nn)
 		.new_timeo = nn->nfsd4_lease
 	};
 	struct nfs4_cpntf_state *cps;
+	struct nfs4_client *clp;
 	copy_stateid_t *cps_t;
 	int i;
 
@@ -7080,6 +7081,18 @@ nfs4_laundromat(struct nfsd_net *nn)
 		dp = list_entry (pos, struct nfs4_delegation, dl_recall_lru);
 		if (!state_expired(&lt, dp->dl_time))
 			break;
+		clp = dp->dl_stid.sc_client;
+		spin_lock(&nn->client_lock);
+		if (is_client_expired(clp)) {
+			spin_unlock(&nn->client_lock);
+			continue;
+		}
+		/*
+		 * Pin without reviving: get_client_locked() would
+		 * flip a courtesy client back to NFSD4_ACTIVE.
+		 */
+		atomic_inc(&clp->cl_rpc_users);
+		spin_unlock(&nn->client_lock);
 		refcount_inc(&dp->dl_stid.sc_count);
 		unhash_delegation_locked(dp, SC_STATUS_REVOKED);
 		list_add(&dp->dl_recall_lru, &reaplist);
@@ -7088,8 +7101,18 @@ nfs4_laundromat(struct nfsd_net *nn)
 	while (!list_empty(&reaplist)) {
 		dp = list_first_entry(&reaplist, struct nfs4_delegation,
 					dl_recall_lru);
+		clp = dp->dl_stid.sc_client;
 		list_del_init(&dp->dl_recall_lru);
 		revoke_delegation(dp);
+		/*
+		 * Unpin without renewing: put_client_renew() would
+		 * renew the reaped client's lease.
+		 */
+		if (atomic_dec_and_lock(&clp->cl_rpc_users, &nn->client_lock)) {
+			if (is_client_expired(clp))
+				wake_up_all(&expiry_wq);
+			spin_unlock(&nn->client_lock);
+		}
 	}
 
 	spin_lock(&nn->client_lock);
-- 
2.53.0

[PATCH 6.18.y 2/4] NFSD: Prevent client use-after-free during admin state revocation

[Sasha Levin]

From: Chuck Lever <cel@kernel.org>

[ Upstream commit e270e5a0778e5bff852c8862ce9576ce70359393 ]

A stateid holds only a bare pointer to its nfs4_client; a stateid
reference does not pin it.  The client survives only because
__destroy_client() drains its stateids before free_client() runs.

nfsd4_revoke_states() drops nn->client_lock across revoke_one_stid(),
which dereferences the client to revoke a stateid and read
clp->cl_minorversion.  A teardown racing the dropped lock can free
the client first.

Pinning cl_rpc_users under client_lock blocks the DESTROY_CLIENTID and
EXCHANGE_ID teardown, which refuses while cl_rpc_users is non-zero.
force_expire_client() ignores it: once its wait for cl_rpc_users to
reach zero has passed, a later pin goes unnoticed.

Under client_lock, skip a client whose cl_time is already zero --
force_expire_client() clears it there before waiting -- otherwise pin
cl_rpc_users before dropping the lock.  The walk then either sees the
expiry and skips, or pins in time for that wait to cover the revoke.

Fixes: 1c13bf9f2e3c ("nfsd: allow lock state ids to be revoked and then freed")
Cc: stable@vger.kernel.org
Reviewed-by: NeilBrown <neil@brown.name>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260709-cel-v4-3-1d519d9be0cb@kernel.org
Signed-off-by: Chuck Lever <cel@kernel.org>
Stable-dep-of: 2330b788d732 ("NFSD: Prevent client use-after-free during close_lru reaping")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/nfsd/nfs4state.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 1453f4769ab98..322f482182afd 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1842,13 +1842,23 @@ void nfsd4_revoke_states(struct nfsd_net *nn, struct super_block *sb)
 		struct nfs4_client *clp;
 	retry:
 		list_for_each_entry(clp, head, cl_idhash) {
-			struct nfs4_stid *stid = find_one_sb_stid(clp, sb,
-								  sc_types);
+			struct nfs4_stid *stid;
+
+			/*
+			 * force_expire_client() ignores cl_rpc_users once
+			 * its wait_event() has passed, so pinning cannot
+			 * keep an already-expiring client alive; the
+			 * expiry path revokes its states instead.
+			 */
+			if (is_client_expired(clp))
+				continue;
+			stid = find_one_sb_stid(clp, sb, sc_types);
 			if (stid) {
 				struct nfs4_ol_stateid *stp;
 				struct nfs4_delegation *dp;
 				struct nfs4_layout_stateid *ls;
 
+				atomic_inc(&clp->cl_rpc_users);
 				spin_unlock(&nn->client_lock);
 				switch (stid->sc_type) {
 				case SC_TYPE_OPEN:
@@ -1932,6 +1942,9 @@ void nfsd4_revoke_states(struct nfsd_net *nn, struct super_block *sb)
 					 */
 					nn->nfs40_last_revoke =
 						ktime_get_boottime_seconds();
+				if (atomic_dec_and_test(&clp->cl_rpc_users) &&
+				    is_client_expired(clp))
+					wake_up_all(&expiry_wq);
 				goto retry;
 			}
 		}
@@ -3218,6 +3231,11 @@ static void force_expire_client(struct nfs4_client *clp)
 
 	trace_nfsd_clid_admin_expired(&clp->cl_clientid);
 
+	/*
+	 * cl_time is cleared under client_lock before the wait so a
+	 * revocation walk pinning cl_rpc_users under it either skips
+	 * this client or is seen by this wait_event().
+	 */
 	spin_lock(&nn->client_lock);
 	clp->cl_time = 0;
 	spin_unlock(&nn->client_lock);
-- 
2.53.0

[PATCH 6.18.y 3/4] NFSD: Consolidate the revocation-path client unpin

[Sasha Levin]

From: Chuck Lever <cel@kernel.org>

[ Upstream commit 3308cf3f11ed23c79f9f3f90b34bbbad3e3a6ea9 ]

The client use-after-free fixes in the state-revocation paths left
four open-coded copies of one idiom: drop a cl_rpc_users pin without
renewing the client's lease, waking force_expire_client() when the
last pin drops on a client it is tearing down.  The accompanying "do
not renew" rationale was documented at only one of the four sites.

put_client_renew_locked() and put_client_renew() already carry the
same pin-drop logic, but they renew a non-expired client's lease and
so would resurrect the client whose state is being revoked.  Factor
the common pin-drop into __put_client_locked(), parameterized by
whether to renew.  The renew helpers pass true; the new
put_client_no_renew_locked() and put_client_no_renew() pass false and
carry the revocation paths, which must not revive the client they are
tearing down.  No change in behavior.

Reviewed-by: NeilBrown <neil@brown.name>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260709-cel-v4-6-1d519d9be0cb@kernel.org
Signed-off-by: Chuck Lever <cel@kernel.org>
Stable-dep-of: 2330b788d732 ("NFSD: Prevent client use-after-free during close_lru reaping")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/nfsd/nfs4state.c | 65 ++++++++++++++++++++++++++++-----------------
 1 file changed, 40 insertions(+), 25 deletions(-)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 322f482182afd..07da5353644e1 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -207,18 +207,28 @@ renew_client_locked(struct nfs4_client *clp)
 	clp->cl_state = NFSD4_ACTIVE;
 }
 
+/*
+ * Finish a cl_rpc_users unpin with the client_lock held. A
+ * revocation walk clears @renew so the client whose state it is
+ * revoking is not revived; every other caller renews the lease of
+ * a still-active client.
+ */
+static void __put_client_locked(struct nfs4_client *clp, bool renew)
+{
+	if (is_client_expired(clp))
+		wake_up_all(&expiry_wq);
+	else if (renew)
+		renew_client_locked(clp);
+}
+
 static void put_client_renew_locked(struct nfs4_client *clp)
 {
 	struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
 
 	lockdep_assert_held(&nn->client_lock);
 
-	if (!atomic_dec_and_test(&clp->cl_rpc_users))
-		return;
-	if (!is_client_expired(clp))
-		renew_client_locked(clp);
-	else
-		wake_up_all(&expiry_wq);
+	if (atomic_dec_and_test(&clp->cl_rpc_users))
+		__put_client_locked(clp, true);
 }
 
 static void put_client_renew(struct nfs4_client *clp)
@@ -227,10 +237,27 @@ static void put_client_renew(struct nfs4_client *clp)
 
 	if (!atomic_dec_and_lock(&clp->cl_rpc_users, &nn->client_lock))
 		return;
-	if (!is_client_expired(clp))
-		renew_client_locked(clp);
-	else
-		wake_up_all(&expiry_wq);
+	__put_client_locked(clp, true);
+	spin_unlock(&nn->client_lock);
+}
+
+static void put_client_no_renew_locked(struct nfs4_client *clp)
+{
+	struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
+
+	lockdep_assert_held(&nn->client_lock);
+
+	if (atomic_dec_and_test(&clp->cl_rpc_users))
+		__put_client_locked(clp, false);
+}
+
+static void put_client_no_renew(struct nfs4_client *clp)
+{
+	struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
+
+	if (!atomic_dec_and_lock(&clp->cl_rpc_users, &nn->client_lock))
+		return;
+	__put_client_locked(clp, false);
 	spin_unlock(&nn->client_lock);
 }
 
@@ -1942,9 +1969,7 @@ void nfsd4_revoke_states(struct nfsd_net *nn, struct super_block *sb)
 					 */
 					nn->nfs40_last_revoke =
 						ktime_get_boottime_seconds();
-				if (atomic_dec_and_test(&clp->cl_rpc_users) &&
-				    is_client_expired(clp))
-					wake_up_all(&expiry_wq);
+				put_client_no_renew_locked(clp);
 				goto retry;
 			}
 		}
@@ -7047,9 +7072,7 @@ static void nfs40_clean_admin_revoked(struct nfsd_net *nn,
 				nfsd4_drop_revoked_stid(stid);
 				nfs4_put_stid(stid);
 				spin_lock(&nn->client_lock);
-				if (atomic_dec_and_test(&clp->cl_rpc_users) &&
-				    is_client_expired(clp))
-					wake_up_all(&expiry_wq);
+				put_client_no_renew_locked(clp);
 				goto retry;
 			}
 		spin_unlock(&clp->cl_lock);
@@ -7122,15 +7145,7 @@ nfs4_laundromat(struct nfsd_net *nn)
 		clp = dp->dl_stid.sc_client;
 		list_del_init(&dp->dl_recall_lru);
 		revoke_delegation(dp);
-		/*
-		 * Unpin without renewing: put_client_renew() would
-		 * renew the reaped client's lease.
-		 */
-		if (atomic_dec_and_lock(&clp->cl_rpc_users, &nn->client_lock)) {
-			if (is_client_expired(clp))
-				wake_up_all(&expiry_wq);
-			spin_unlock(&nn->client_lock);
-		}
+		put_client_no_renew(clp);
 	}
 
 	spin_lock(&nn->client_lock);
-- 
2.53.0

[PATCH 6.18.y 4/4] NFSD: Prevent client use-after-free during close_lru reaping

[Sasha Levin]

From: Chuck Lever <cel@kernel.org>

[ Upstream commit 2330b788d732f43668b965b3105b37ceb276dfea ]

An nfs4_openowner left on nn->close_lru after its final CLOSE keeps
its last closed stateid in oo_last_closed_stid, holding only a raw
pointer to its nfs4_client. The laundromat reaps timed-out entries,
drops nn->client_lock, and calls nfs4_put_stid(), which dereferences
the client through cl_lock. Nothing pins the client across that
window, so a concurrent force_expire_client() can free it and
nfs4_put_stid() reads freed memory. __destroy_client() hits the same
race, walking clp->cl_openowners without cl_lock.

Pin the client with cl_rpc_users before dropping client_lock, and
skip clients already expiring. __destroy_client() then cleans up its
own close_lru entries through release_last_closed_stateid(), so
teardown no longer races the laundromat.

Fixes: 217526e7ecc9 ("nfsd: protect the close_lru list and oo_last_closed_stid with client_lock")
Cc: stable@vger.kernel.org
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260709-cel-v4-8-1d519d9be0cb@kernel.org
Signed-off-by: Chuck Lever <cel@kernel.org>
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 07da5353644e1..d8c44eddf38ed 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -7155,11 +7155,16 @@ nfs4_laundromat(struct nfsd_net *nn)
 		if (!state_expired(&lt, oo->oo_time))
 			break;
 		list_del_init(&oo->oo_close_lru);
+		clp = oo->oo_owner.so_client;
+		if (is_client_expired(clp))
+			continue;
 		stp = oo->oo_last_closed_stid;
 		oo->oo_last_closed_stid = NULL;
+		atomic_inc(&clp->cl_rpc_users);
 		spin_unlock(&nn->client_lock);
 		nfs4_put_stid(&stp->st_stid);
 		spin_lock(&nn->client_lock);
+		put_client_no_renew_locked(clp);
 	}
 	spin_unlock(&nn->client_lock);
 
-- 
2.53.0