[SRU][Jammy][PATCH 1/1] ksmbd: destroy expired sessions

[Bethany Jamison]

From: Namjae Jeon <linkinjeon at kernel.org>

client can indefinitely send smb2 session setup requests with
the SessionId set to 0, thus indefinitely spawning new sessions,
and causing indefinite memory usage. This patch limit to the number
of sessions using expired timeout and session state.

Cc: stable at vger.kernel.org
Reported-by: zdi-disclosures at trendmicro.com # ZDI-CAN-20478
Signed-off-by: Namjae Jeon <linkinjeon at kernel.org>
Signed-off-by: Steve French <stfrench at microsoft.com>
(backported from commit ea174a91893956450510945a0c5d1a10b5323656)
[bjamison: Jammy code structure was different in smb2pdu.h than
upstream - found relevant code chunk and implemented fix commit's
intended change]
CVE-2023-32247
Signed-off-by: Bethany Jamison <bethany.jamison at canonical.com>
---
 fs/ksmbd/mgmt/user_session.c | 68 ++++++++++++++++++++----------------
 fs/ksmbd/mgmt/user_session.h |  1 +
 fs/ksmbd/smb2pdu.c           |  1 +
 fs/ksmbd/smb2pdu.h           |  2 ++
 4 files changed, 41 insertions(+), 31 deletions(-)

diff --git a/fs/ksmbd/mgmt/user_session.c b/fs/ksmbd/mgmt/user_session.c
index 69b85a98e2c35..b809f7987b9f4 100644
--- a/fs/ksmbd/mgmt/user_session.c
+++ b/fs/ksmbd/mgmt/user_session.c
@@ -174,70 +174,73 @@ static struct ksmbd_session *__session_lookup(unsigned long long id)
 	struct ksmbd_session *sess;
 
 	hash_for_each_possible(sessions_table, sess, hlist, id) {
-		if (id == sess->id)
+		if (id == sess->id) {
+			sess->last_active = jiffies;
 			return sess;
+		}
 	}
 	return NULL;
 }
 
+static void ksmbd_expire_session(struct ksmbd_conn *conn)
+{
+	unsigned long id;
+	struct ksmbd_session *sess;
+
+	xa_for_each(&conn->sessions, id, sess) {
+		if (sess->state != SMB2_SESSION_VALID ||
+		    time_after(jiffies,
+			       sess->last_active + SMB2_SESSION_TIMEOUT)) {
+			xa_erase(&conn->sessions, sess->id);
+			ksmbd_session_destroy(sess);
+			continue;
+		}
+	}
+}
+
 int ksmbd_session_register(struct ksmbd_conn *conn,
 			   struct ksmbd_session *sess)
 {
 	sess->dialect = conn->dialect;
 	memcpy(sess->ClientGUID, conn->ClientGUID, SMB2_CLIENT_GUID_SIZE);
+	ksmbd_expire_session(conn);
 	return xa_err(xa_store(&conn->sessions, sess->id, sess, GFP_KERNEL));
 }
 
-static int ksmbd_chann_del(struct ksmbd_conn *conn, struct ksmbd_session *sess)
+static void ksmbd_chann_del(struct ksmbd_conn *conn, struct ksmbd_session *sess)
 {
 	struct channel *chann;
 
 	chann = xa_erase(&sess->ksmbd_chann_list, (long)conn);
 	if (!chann)
-		return -ENOENT;
+		return;
 
 	kfree(chann);
-
-	return 0;
 }
 
 void ksmbd_sessions_deregister(struct ksmbd_conn *conn)
 {
 	struct ksmbd_session *sess;
+	unsigned long id;
 
-	if (conn->binding) {
-		int bkt;
-
-		down_write(&sessions_table_lock);
-		hash_for_each(sessions_table, bkt, sess, hlist) {
-			if (!ksmbd_chann_del(conn, sess)) {
-				up_write(&sessions_table_lock);
-				goto sess_destroy;
-			}
+	xa_for_each(&conn->sessions, id, sess) {
+		ksmbd_chann_del(conn, sess);
+		if (xa_empty(&sess->ksmbd_chann_list)) {
+			xa_erase(&conn->sessions, sess->id);
+			ksmbd_session_destroy(sess);
 		}
-		up_write(&sessions_table_lock);
-	} else {
-		unsigned long id;
-
-		xa_for_each(&conn->sessions, id, sess) {
-			if (!ksmbd_chann_del(conn, sess))
-				goto sess_destroy;
-		}
-	}
-
-	return;
-
-sess_destroy:
-	if (xa_empty(&sess->ksmbd_chann_list)) {
-		xa_erase(&conn->sessions, sess->id);
-		ksmbd_session_destroy(sess);
 	}
 }
 
 struct ksmbd_session *ksmbd_session_lookup(struct ksmbd_conn *conn,
 					   unsigned long long id)
 {
-	return xa_load(&conn->sessions, id);
+	struct ksmbd_session *sess;
+
+	sess = xa_load(&conn->sessions, id);
+	if (sess)
+		sess->last_active = jiffies;
+	return sess;
 }
 
 struct ksmbd_session *ksmbd_session_lookup_slowpath(unsigned long long id)
@@ -246,6 +249,8 @@ struct ksmbd_session *ksmbd_session_lookup_slowpath(unsigned long long id)
 
 	down_read(&sessions_table_lock);
 	sess = __session_lookup(id);
+	if (sess)
+		sess->last_active = jiffies;
 	up_read(&sessions_table_lock);
 
 	return sess;
@@ -324,6 +329,7 @@ static struct ksmbd_session *__session_create(int protocol)
 	if (ksmbd_init_file_table(&sess->file_table))
 		goto error;
 
+	sess->last_active = jiffies;
 	sess->state = SMB2_SESSION_IN_PROGRESS;
 	set_session_flag(sess, protocol);
 	xa_init(&sess->tree_conns);
diff --git a/fs/ksmbd/mgmt/user_session.h b/fs/ksmbd/mgmt/user_session.h
index 44a3c67b2bd92..51f38e5b61abb 100644
--- a/fs/ksmbd/mgmt/user_session.h
+++ b/fs/ksmbd/mgmt/user_session.h
@@ -59,6 +59,7 @@ struct ksmbd_session {
 	__u8				smb3signingkey[SMB3_SIGN_KEY_SIZE];
 
 	struct ksmbd_file_table		file_table;
+	unsigned long			last_active;
 };
 
 static inline int test_session_flag(struct ksmbd_session *sess, int bit)
diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
index 8f438a3f3d0bb..89af3a6b8fb75 100644
--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -1895,6 +1895,7 @@ int smb2_sess_setup(struct ksmbd_work *work)
 			if (sess->user && sess->user->flags & KSMBD_USER_FLAG_DELAY_SESSION)
 				try_delay = true;
 
+			sess->last_active = jiffies;
 			sess->state = SMB2_SESSION_EXPIRED;
 			if (try_delay)
 				ssleep(5);
diff --git a/fs/ksmbd/smb2pdu.h b/fs/ksmbd/smb2pdu.h
index fa1cd556ab7ac..ef254243a7359 100644
--- a/fs/ksmbd/smb2pdu.h
+++ b/fs/ksmbd/smb2pdu.h
@@ -376,6 +376,8 @@ struct smb2_negotiate_rsp {
 #define SMB2_SESSION_IN_PROGRESS	BIT(0)
 #define SMB2_SESSION_VALID		BIT(1)
 
+#define SMB2_SESSION_TIMEOUT		(10 * HZ)
+
 /* Flags */
 #define SMB2_SESSION_REQ_FLAG_BINDING		0x01
 #define SMB2_SESSION_REQ_FLAG_ENCRYPT_DATA	0x04
-- 
2.34.1