ksmbd: destroy expired sessions

[ Upstream commit ea174a91893956450510945a0c5d1a10b5323656 ]

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@vger.kernel.org
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-20478
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/ksmbd/mgmt/user_session.c b/fs/ksmbd/mgmt/user_session.c
index 69b85a98e2c358b26cde630970a9fa18674249d1..b809f7987b9f4ffeb0f7734b3377b62ad69486d4 100644 (file)
--- 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 44a3c67b2bd9232714660df959ad098c593d07fa..51f38e5b61abb48f235ccdc34aa4a8b96e1901f0 100644 (file)
--- 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 6c26934272ad5abf7830982c5bc7e6d3ebdb8659..d3f33194faf1aaa3b728b221011874232b88905b 100644 (file)
--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -1860,6 +1860,7 @@ 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 f4baa9800f6ee4e0688ef16ec7734a06827d4b34..dd10f8031606b7fc80e88e389b3936f4e331e567 100644 (file)
--- a/fs/ksmbd/smb2pdu.h
+++ b/fs/ksmbd/smb2pdu.h
@@ -61,6 +61,8 @@ struct preauth_integrity_info {
 #define SMB2_SESSION_IN_PROGRESS       BIT(0)
 #define SMB2_SESSION_VALID             BIT(1)
 
+#define SMB2_SESSION_TIMEOUT           (10 * HZ)
+
 struct create_durable_req_v2 {
        struct create_context ccontext;
        __u8   Name[8];