Merge tag 'v7.2-rc5-smb3-server-fixes' of git://git.samba.org/ksmbd

Pull smb server fixes from Steve French:

 - Use memcmp() when comparing fixed-size binary ClientGUIDs, so
   embedded NUL bytes are handled correctly

 - Reject repeated SMB2 NEGOTIATE requests after dialect selection

   This prevents preauth_info leaks, enforces the SMB2 protocol
   requirements, and serializes negotiation state updates.

 - Fix a use-after-free in __close_file_table_ids() by removing the
   volatile file ID from the owning IDR before dropping the IDR
   reference

* tag 'v7.2-rc5-smb3-server-fixes' of git://git.samba.org/ksmbd:
  ksmbd: use memcmp() to compare ClientGUIDs
  ksmbd: reject repeated SMB2 NEGOTIATE requests
  ksmbd: fix use-after-free in __close_file_table_ids()

4 files changed, 41 insertions, 17 deletions

diff --git a/fs/smb/server/connection.h b/fs/smb/server/connection.h
index ec75633b7da0..2a194ee36fb4 100644
--- a/fs/smb/server/connection.h
+++ b/fs/smb/server/connection.h
@@ -200,6 +200,11 @@ void ksmbd_conn_r_count_dec(struct ksmbd_conn *conn);
  * This is a hack. We will move status to a proper place once we land
  * a multi-sessions support.
  */
+static inline bool ksmbd_conn_new(struct ksmbd_conn *conn)
+{
+	return READ_ONCE(conn->status) == KSMBD_SESS_NEW;
+}
+
 static inline bool ksmbd_conn_good(struct ksmbd_conn *conn)
 {
 	return READ_ONCE(conn->status) == KSMBD_SESS_GOOD;
diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c
index c1ba5e01aa7f..76f63f9adc72 100644
--- a/fs/smb/server/smb2pdu.c
+++ b/fs/smb/server/smb2pdu.c
@@ -1325,6 +1325,8 @@ static __le32 deassemble_neg_contexts(struct ksmbd_conn *conn,
  * smb2_handle_negotiate() - handler for smb2 negotiate command
  * @work:	smb work containing smb request buffer
  *
+ * The caller holds conn->srv_mutex.
+ *
  * Return:      0
  */
 int smb2_handle_negotiate(struct ksmbd_work *work)
@@ -1338,13 +1340,6 @@ int smb2_handle_negotiate(struct ksmbd_work *work)
 
 	ksmbd_debug(SMB, "Received negotiate request\n");
 	conn->need_neg = false;
-	if (ksmbd_conn_good(conn)) {
-		pr_err("conn->tcp_status is already in CifsGood State\n");
-		work->send_no_response = 1;
-		return rc;
-	}
-
-	ksmbd_conn_lock(conn);
 	smb2_buf_len = get_rfc1002_len(work->request_buf);
 	smb2_neg_size = offsetof(struct smb2_negotiate_req, Dialects);
 	if (smb2_neg_size > smb2_buf_len) {
@@ -1495,7 +1490,6 @@ int smb2_handle_negotiate(struct ksmbd_work *work)
 	ksmbd_conn_set_need_setup(conn);
 
 err_out:
-	ksmbd_conn_unlock(conn);
 	if (rc)
 		rsp->hdr.Status = STATUS_INSUFFICIENT_RESOURCES;
 
@@ -1975,7 +1969,7 @@ int smb2_sess_setup(struct ksmbd_work *work)
 			goto out_err;
 		}
 
-		if (strncmp(conn->ClientGUID, sess->ClientGUID,
+		if (memcmp(conn->ClientGUID, sess->ClientGUID,
 			    SMB2_CLIENT_GUID_SIZE)) {
 			rc = -ENOENT;
 			goto out_err;
@@ -8696,7 +8690,7 @@ static int fsctl_validate_negotiate_info(struct ksmbd_conn *conn,
 		goto err_out;
 	}
 
-	if (strncmp(neg_req->Guid, conn->ClientGUID, SMB2_CLIENT_GUID_SIZE)) {
+	if (memcmp(neg_req->Guid, conn->ClientGUID, SMB2_CLIENT_GUID_SIZE)) {
 		ret = -EINVAL;
 		goto err_out;
 	}
diff --git a/fs/smb/server/smb_common.c b/fs/smb/server/smb_common.c
index 7de73223189a..080fbc9eb470 100644
--- a/fs/smb/server/smb_common.c
+++ b/fs/smb/server/smb_common.c
@@ -608,23 +608,46 @@ int ksmbd_smb_negotiate_common(struct ksmbd_work *work, unsigned int command)
 	struct ksmbd_conn *conn = work->conn;
 	int ret;
 
-	conn->dialect =
-		ksmbd_negotiate_smb_dialect(work->request_buf);
-	ksmbd_debug(SMB, "conn->dialect 0x%x\n", conn->dialect);
-
 	if (command == SMB2_NEGOTIATE_HE) {
+		/*
+		 * An SMB2 NEGOTIATE is valid for a new connection, or after an
+		 * SMB1 multi-protocol negotiate has selected SMB2. Do not allow
+		 * a second SMB2 NEGOTIATE to replace connection-wide state
+		 * while a session setup is pending. KSMBD_SESS_NEED_RECONNECT
+		 * is a transient session state and does not restart transport
+		 * negotiation.
+		 */
+		ksmbd_conn_lock(conn);
+		if (!ksmbd_conn_new(conn) &&
+		    !ksmbd_conn_need_negotiate(conn)) {
+			work->send_no_response = 1;
+			ksmbd_conn_set_exiting(conn);
+			ksmbd_conn_unlock(conn);
+			return 0;
+		}
+
+		conn->dialect =
+			ksmbd_negotiate_smb_dialect(work->request_buf);
+		ksmbd_debug(SMB, "conn->dialect 0x%x\n", conn->dialect);
 		ret = smb2_handle_negotiate(work);
+		ksmbd_conn_unlock(conn);
 		return ret;
 	}
 
 	if (command == SMB_COM_NEGOTIATE) {
+		ksmbd_conn_lock(conn);
+		conn->dialect =
+			ksmbd_negotiate_smb_dialect(work->request_buf);
+		ksmbd_debug(SMB, "conn->dialect 0x%x\n", conn->dialect);
 		if (__smb2_negotiate(conn)) {
 			init_smb3_11_server(conn);
-			init_smb2_neg_rsp(work);
+			ret = init_smb2_neg_rsp(work);
 			ksmbd_debug(SMB, "Upgrade to SMB2 negotiation\n");
-			return 0;
+		} else {
+			ret = smb_handle_negotiate(work);
 		}
-		return smb_handle_negotiate(work);
+		ksmbd_conn_unlock(conn);
+		return ret;
 	}
 
 	pr_err("Unknown SMB negotiation command: %u\n", command);
diff --git a/fs/smb/server/vfs_cache.c b/fs/smb/server/vfs_cache.c
index d95c405eab11..a141025581af 100644
--- a/fs/smb/server/vfs_cache.c
+++ b/fs/smb/server/vfs_cache.c
@@ -697,6 +697,8 @@ int ksmbd_close_fd(struct ksmbd_work *work, u64 id)
 			fp = NULL;
 		else {
 			fp->f_state = FP_CLOSED;
+			idr_remove(ft->idr, id);
+			fp->volatile_id = KSMBD_NO_FID;
 			closed = true;
 			if (!atomic_dec_and_test(&fp->refcount))
 				fp = NULL;