Merge tag 'v6.15rc-part2-ksmbd-server-fixes' of git://git.samba.org/ksmbd

Pull smb server fixes from Steve French:
 "Four ksmbd SMB3 server fixes, all also for stable"

* tag 'v6.15rc-part2-ksmbd-server-fixes' of git://git.samba.org/ksmbd:
  ksmbd: fix null pointer dereference in alloc_preauth_hash()
  ksmbd: validate zero num_subauth before sub_auth is accessed
  ksmbd: fix overflow in dacloffset bounds check
  ksmbd: fix session use-after-free in multichannel connection

Author: torvalds

fs/smb/server/auth.c

@@ -1016,9 +1016,9 @@ static int ksmbd_get_encryption_key(struct ksmbd_work *work, __u64 ses_id,
 
 	ses_enc_key = enc ? sess->smb3encryptionkey :
 		sess->smb3decryptionkey;
-	if (enc)
-		ksmbd_user_session_get(sess);
 	memcpy(key, ses_enc_key, SMB3_ENC_DEC_KEY_SIZE);
+	if (!enc)
+		ksmbd_user_session_put(sess);
 
 	return 0;
 }

fs/smb/server/connection.h

@@ -27,6 +27,7 @@ enum {
 	KSMBD_SESS_EXITING,
 	KSMBD_SESS_NEED_RECONNECT,
 	KSMBD_SESS_NEED_NEGOTIATE,
+	KSMBD_SESS_NEED_SETUP,
 	KSMBD_SESS_RELEASING
 };
 
@@ -187,6 +188,11 @@ static inline bool ksmbd_conn_need_negotiate(struct ksmbd_conn *conn)
 	return READ_ONCE(conn->status) == KSMBD_SESS_NEED_NEGOTIATE;
 }
 
+static inline bool ksmbd_conn_need_setup(struct ksmbd_conn *conn)
+{
+	return READ_ONCE(conn->status) == KSMBD_SESS_NEED_SETUP;
+}
+
 static inline bool ksmbd_conn_need_reconnect(struct ksmbd_conn *conn)
 {
 	return READ_ONCE(conn->status) == KSMBD_SESS_NEED_RECONNECT;
@@ -217,6 +223,11 @@ static inline void ksmbd_conn_set_need_negotiate(struct ksmbd_conn *conn)
 	WRITE_ONCE(conn->status, KSMBD_SESS_NEED_NEGOTIATE);
 }
 
+static inline void ksmbd_conn_set_need_setup(struct ksmbd_conn *conn)
+{
+	WRITE_ONCE(conn->status, KSMBD_SESS_NEED_SETUP);
+}
+
 static inline void ksmbd_conn_set_need_reconnect(struct ksmbd_conn *conn)
 {
 	WRITE_ONCE(conn->status, KSMBD_SESS_NEED_RECONNECT);

fs/smb/server/mgmt/user_session.c

@@ -181,7 +181,7 @@ static void ksmbd_expire_session(struct ksmbd_conn *conn)
 	down_write(&sessions_table_lock);
 	down_write(&conn->session_lock);
 	xa_for_each(&conn->sessions, id, sess) {
-		if (atomic_read(&sess->refcnt) == 0 &&
+		if (atomic_read(&sess->refcnt) <= 1 &&
 		    (sess->state != SMB2_SESSION_VALID ||
 		     time_after(jiffies,
 			       sess->last_active + SMB2_SESSION_TIMEOUT))) {
@@ -233,7 +233,8 @@ void ksmbd_sessions_deregister(struct ksmbd_conn *conn)
 				down_write(&conn->session_lock);
 				xa_erase(&conn->sessions, sess->id);
 				up_write(&conn->session_lock);
-				ksmbd_session_destroy(sess);
+				if (atomic_dec_and_test(&sess->refcnt))
+					ksmbd_session_destroy(sess);
 			}
 		}
 	}
@@ -252,7 +253,8 @@ void ksmbd_sessions_deregister(struct ksmbd_conn *conn)
 		if (xa_empty(&sess->ksmbd_chann_list)) {
 			xa_erase(&conn->sessions, sess->id);
 			hash_del(&sess->hlist);
-			ksmbd_session_destroy(sess);
+			if (atomic_dec_and_test(&sess->refcnt))
+				ksmbd_session_destroy(sess);
 		}
 	}
 	up_write(&conn->session_lock);
@@ -328,8 +330,8 @@ void ksmbd_user_session_put(struct ksmbd_session *sess)
 
 	if (atomic_read(&sess->refcnt) <= 0)
 		WARN_ON(1);
-	else
-		atomic_dec(&sess->refcnt);
+	else if (atomic_dec_and_test(&sess->refcnt))
+		ksmbd_session_destroy(sess);
 }
 
 struct preauth_session *ksmbd_preauth_session_alloc(struct ksmbd_conn *conn,
@@ -372,13 +374,13 @@ void destroy_previous_session(struct ksmbd_conn *conn,
 	ksmbd_all_conn_set_status(id, KSMBD_SESS_NEED_RECONNECT);
 	err = ksmbd_conn_wait_idle_sess_id(conn, id);
 	if (err) {
-		ksmbd_all_conn_set_status(id, KSMBD_SESS_NEED_NEGOTIATE);
+		ksmbd_all_conn_set_status(id, KSMBD_SESS_NEED_SETUP);
 		goto out;
 	}
 
 	ksmbd_destroy_file_table(&prev_sess->file_table);
 	prev_sess->state = SMB2_SESSION_EXPIRED;
-	ksmbd_all_conn_set_status(id, KSMBD_SESS_NEED_NEGOTIATE);
+	ksmbd_all_conn_set_status(id, KSMBD_SESS_NEED_SETUP);
 	ksmbd_launch_ksmbd_durable_scavenger();
 out:
 	up_write(&conn->session_lock);
@@ -436,7 +438,7 @@ static struct ksmbd_session *__session_create(int protocol)
 	xa_init(&sess->rpc_handle_list);
 	sess->sequence_number = 1;
 	rwlock_init(&sess->tree_conns_lock);
-	atomic_set(&sess->refcnt, 1);
+	atomic_set(&sess->refcnt, 2);
 
 	ret = __init_smb2_session(sess);
 	if (ret)

fs/smb/server/smb2pdu.c

@@ -1249,7 +1249,7 @@ int smb2_handle_negotiate(struct ksmbd_work *work)
 	}
 
 	conn->srv_sec_mode = le16_to_cpu(rsp->SecurityMode);
-	ksmbd_conn_set_need_negotiate(conn);
+	ksmbd_conn_set_need_setup(conn);
 
 err_out:
 	ksmbd_conn_unlock(conn);
@@ -1271,6 +1271,9 @@ static int alloc_preauth_hash(struct ksmbd_session *sess,
 	if (sess->Preauth_HashValue)
 		return 0;
 
+	if (!conn->preauth_info)
+		return -ENOMEM;
+
 	sess->Preauth_HashValue = kmemdup(conn->preauth_info->Preauth_HashValue,
 					  PREAUTH_HASHVALUE_SIZE, KSMBD_DEFAULT_GFP);
 	if (!sess->Preauth_HashValue)
@@ -1674,6 +1677,11 @@ int smb2_sess_setup(struct ksmbd_work *work)
 
 	ksmbd_debug(SMB, "Received smb2 session setup request\n");
 
+	if (!ksmbd_conn_need_setup(conn) && !ksmbd_conn_good(conn)) {
+		work->send_no_response = 1;
+		return rc;
+	}
+
 	WORK_BUFFERS(work, req, rsp);
 
 	rsp->StructureSize = cpu_to_le16(9);
@@ -1909,7 +1917,7 @@ int smb2_sess_setup(struct ksmbd_work *work)
 			if (try_delay) {
 				ksmbd_conn_set_need_reconnect(conn);
 				ssleep(5);
-				ksmbd_conn_set_need_negotiate(conn);
+				ksmbd_conn_set_need_setup(conn);
 			}
 		}
 		smb2_set_err_rsp(work);
@@ -2235,14 +2243,15 @@ int smb2_session_logoff(struct ksmbd_work *work)
 		return -ENOENT;
 	}
 
-	ksmbd_destroy_file_table(&sess->file_table);
 	down_write(&conn->session_lock);
 	sess->state = SMB2_SESSION_EXPIRED;
 	up_write(&conn->session_lock);
 
-	ksmbd_free_user(sess->user);
-	sess->user = NULL;
-	ksmbd_all_conn_set_status(sess_id, KSMBD_SESS_NEED_NEGOTIATE);
+	if (sess->user) {
+		ksmbd_free_user(sess->user);
+		sess->user = NULL;
+	}
+	ksmbd_all_conn_set_status(sess_id, KSMBD_SESS_NEED_SETUP);
 
 	rsp->StructureSize = cpu_to_le16(4);
 	err = ksmbd_iov_pin_rsp(work, rsp, sizeof(struct smb2_logoff_rsp));

fs/smb/server/smbacl.c

@@ -270,6 +270,11 @@ static int sid_to_id(struct mnt_idmap *idmap,
 		return -EIO;
 	}
 
+	if (psid->num_subauth == 0) {
+		pr_err("%s: zero subauthorities!\n", __func__);
+		return -EIO;
+	}
+
 	if (sidtype == SIDOWNER) {
 		kuid_t uid;
 		uid_t id;
@@ -1026,7 +1031,9 @@ int smb_inherit_dacl(struct ksmbd_conn *conn,
 	struct dentry *parent = path->dentry->d_parent;
 	struct mnt_idmap *idmap = mnt_idmap(path->mnt);
 	int inherited_flags = 0, flags = 0, i, nt_size = 0, pdacl_size;
-	int rc = 0, dacloffset, pntsd_type, pntsd_size, acl_len, aces_size;
+	int rc = 0, pntsd_type, pntsd_size, acl_len, aces_size;
+	unsigned int dacloffset;
+	size_t dacl_struct_end;
 	u16 num_aces, ace_cnt = 0;
 	char *aces_base;
 	bool is_dir = S_ISDIR(d_inode(path->dentry)->i_mode);
@@ -1035,8 +1042,11 @@ int smb_inherit_dacl(struct ksmbd_conn *conn,
 					    parent, &parent_pntsd);
 	if (pntsd_size <= 0)
 		return -ENOENT;
+
 	dacloffset = le32_to_cpu(parent_pntsd->dacloffset);
-	if (!dacloffset || (dacloffset + sizeof(struct smb_acl) > pntsd_size)) {
+	if (!dacloffset ||
+	    check_add_overflow(dacloffset, sizeof(struct smb_acl), &dacl_struct_end) ||
+	    dacl_struct_end > (size_t)pntsd_size) {
 		rc = -EINVAL;
 		goto free_parent_pntsd;
 	}
@@ -1240,7 +1250,9 @@ int smb_check_perm_dacl(struct ksmbd_conn *conn, const struct path *path,
 	struct smb_ntsd *pntsd = NULL;
 	struct smb_acl *pdacl;
 	struct posix_acl *posix_acls;
-	int rc = 0, pntsd_size, acl_size, aces_size, pdacl_size, dacl_offset;
+	int rc = 0, pntsd_size, acl_size, aces_size, pdacl_size;
+	unsigned int dacl_offset;
+	size_t dacl_struct_end;
 	struct smb_sid sid;
 	int granted = le32_to_cpu(*pdaccess & ~FILE_MAXIMAL_ACCESS_LE);
 	struct smb_ace *ace;
@@ -1259,7 +1271,8 @@ int smb_check_perm_dacl(struct ksmbd_conn *conn, const struct path *path,
 
 	dacl_offset = le32_to_cpu(pntsd->dacloffset);
 	if (!dacl_offset ||
-	    (dacl_offset + sizeof(struct smb_acl) > pntsd_size))
+	    check_add_overflow(dacl_offset, sizeof(struct smb_acl), &dacl_struct_end) ||
+	    dacl_struct_end > (size_t)pntsd_size)
 		goto err_out;
 
 	pdacl = (struct smb_acl *)((char *)pntsd + le32_to_cpu(pntsd->dacloffset));