[PATCH 2/2] ksmbd: limit pdu length size according to connection status

From: Namjae Jeon <linkinjeon@kernel.org>
To: linux-cifs@vger.kernel.org
Cc: smfrench@gmail.com, senozhatsky@chromium.org, tom@talpey.com,
	Namjae Jeon <linkinjeon@kernel.org>
Subject: [PATCH 2/2] ksmbd: limit pdu length size according to connection status
Date: Wed, 25 Jan 2023 00:16:03 +0900	[thread overview]
Message-ID: <20230124151603.18398-2-linkinjeon@kernel.org> (raw)
In-Reply-To: <20230124151603.18398-1-linkinjeon@kernel.org>

Stream protocol length will never be larger than 16KB until session setup.
After session setup, the size of requests will not be larger than
16KB + SMB2 MAX WRITE size. This patch limits these invalidly oversized
requests and closes the connection immediately.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
---
 fs/ksmbd/connection.c | 17 +++++++++++++++--
 fs/ksmbd/smb2pdu.h    |  5 +++--
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/fs/ksmbd/connection.c b/fs/ksmbd/connection.c
index 5be203029bef..ee57db106c1e 100644
--- a/fs/ksmbd/connection.c
+++ b/fs/ksmbd/connection.c
@@ -280,7 +280,7 @@ int ksmbd_conn_handler_loop(void *p)
 {
 	struct ksmbd_conn *conn = (struct ksmbd_conn *)p;
 	struct ksmbd_transport *t = conn->transport;
-	unsigned int pdu_size;
+	unsigned int pdu_size, max_allowed_pdu_size;
 	char hdr_buf[4] = {0,};
 	int size;
 
@@ -305,13 +305,26 @@ int ksmbd_conn_handler_loop(void *p)
 		pdu_size = get_rfc1002_len(hdr_buf);
 		ksmbd_debug(CONN, "RFC1002 header %u bytes\n", pdu_size);
 
+		if (conn->status == KSMBD_SESS_GOOD)
+			max_allowed_pdu_size =
+				SMB3_MAX_MSGSIZE + conn->vals->max_write_size;
+		else
+			max_allowed_pdu_size = SMB3_MAX_MSGSIZE;
+
+		if (pdu_size > max_allowed_pdu_size) {
+			pr_err_ratelimited("PDU length(%u) excceed maximum allowed pdu size(%u) on connection(%d)\n",
+					pdu_size, max_allowed_pdu_size,
+					conn->status);
+			break;
+		}
+
 		/*
 		 * Check if pdu size is valid (min : smb header size,
 		 * max : 0x00FFFFFF).
 		 */
 		if (pdu_size < __SMB2_HEADER_STRUCTURE_SIZE ||
 		    pdu_size > MAX_STREAM_PROT_LEN) {
-			continue;
+			break;
 		}
 
 		/* 4 for rfc1002 length field */
diff --git a/fs/ksmbd/smb2pdu.h b/fs/ksmbd/smb2pdu.h
index aa5dbe54f5a1..0c8a770fe318 100644
--- a/fs/ksmbd/smb2pdu.h
+++ b/fs/ksmbd/smb2pdu.h
@@ -24,8 +24,9 @@
 
 #define SMB21_DEFAULT_IOSIZE	(1024 * 1024)
 #define SMB3_DEFAULT_TRANS_SIZE	(1024 * 1024)
-#define SMB3_MIN_IOSIZE	(64 * 1024)
-#define SMB3_MAX_IOSIZE	(8 * 1024 * 1024)
+#define SMB3_MIN_IOSIZE		(64 * 1024)
+#define SMB3_MAX_IOSIZE		(8 * 1024 * 1024)
+#define SMB3_MAX_MSGSIZE	(4 * 4096)
 
 /*
  *	Definitions for SMB2 Protocol Data Units (network frames)
-- 
2.25.1

