ksmbd: fix racy issue under cocurrent smb2 tree disconnect

There is UAF issue under cocurrent smb2 tree disconnect.
This patch introduce TREE_CONN_EXPIRE flags for tcon to avoid cocurrent
access.

Cc: stable@vger.kernel.org
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-20592
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/ksmbd/mgmt/tree_connect.c b/fs/ksmbd/mgmt/tree_connect.c
index aa9c138..f07a05f 100644 (file)
--- a/fs/ksmbd/mgmt/tree_connect.c
+++ b/fs/ksmbd/mgmt/tree_connect.c
@@ -109,7 +109,15 @@ int ksmbd_tree_conn_disconnect(struct ksmbd_session *sess,
 struct ksmbd_tree_connect *ksmbd_tree_conn_lookup(struct ksmbd_session *sess,
                                                  unsigned int id)
 {
-       return xa_load(&sess->tree_conns, id);
+       struct ksmbd_tree_connect *tcon;
+
+       tcon = xa_load(&sess->tree_conns, id);
+       if (tcon) {
+               if (test_bit(TREE_CONN_EXPIRE, &tcon->status))
+                       tcon = NULL;
+       }
+
+       return tcon;
 }
 
 struct ksmbd_share_config *ksmbd_tree_conn_share(struct ksmbd_session *sess,

diff --git a/fs/ksmbd/mgmt/tree_connect.h b/fs/ksmbd/mgmt/tree_connect.h
index 0f97ddc..700df36 100644 (file)
--- a/fs/ksmbd/mgmt/tree_connect.h
+++ b/fs/ksmbd/mgmt/tree_connect.h
@@ -14,6 +14,8 @@ struct ksmbd_share_config;
 struct ksmbd_user;
 struct ksmbd_conn;
 
+#define TREE_CONN_EXPIRE               1
+
 struct ksmbd_tree_connect {
        int                             id;
 
@@ -25,6 +27,7 @@ struct ksmbd_tree_connect {
 
        int                             maximal_access;
        bool                            posix_extensions;
+       unsigned long                   status;
 };
 
 struct ksmbd_tree_conn_status {

diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
index 0ca1c5d..cb93fd2 100644 (file)
--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -2053,11 +2053,12 @@ int smb2_tree_disconnect(struct ksmbd_work *work)
 
        ksmbd_debug(SMB, "request\n");
 
-       if (!tcon) {
+       if (!tcon || test_and_set_bit(TREE_CONN_EXPIRE, &tcon->status)) {
                struct smb2_tree_disconnect_req *req =
                        smb2_get_msg(work->request_buf);
 
                ksmbd_debug(SMB, "Invalid tid %d\n", req->hdr.Id.SyncId.TreeId);
+
                rsp->hdr.Status = STATUS_NETWORK_NAME_DELETED;
                smb2_set_err_rsp(work);
                return 0;