[UBUNTU Jammy 1/1] ksmbd: validate length in smb2_write()

[Thadeu Lima de Souza Cascardo]

From: Marios Makassikis <mmakassikis at freebox.fr>

The SMB2 Write packet contains data that is to be written
to a file or to a pipe. Depending on the client, there may
be padding between the header and the data field.
Currently, the length is validated only in the case padding
is present.

Since the DataOffset field always points to the beginning
of the data, there is no need to have a special case for
padding. By removing this, the length is validated in both
cases.

Signed-off-by: Marios Makassikis <mmakassikis at freebox.fr>
Acked-by: Namjae Jeon <linkinjeon at kernel.org>
Signed-off-by: Steve French <stfrench at microsoft.com>
(backported from commit 158a66b245739e15858de42c0ba60fcf3de9b8e6)
CVE-2022-47940
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo at canonical.com>
---
 fs/ksmbd/smb2pdu.c | 42 ++++++++++++++++--------------------------
 1 file changed, 16 insertions(+), 26 deletions(-)

diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
index 55ee639703ff..5c63d29bf603 100644
--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -6321,22 +6321,17 @@ static noinline int smb2_write_pipe(struct ksmbd_work *work)
 	length = le32_to_cpu(req->Length);
 	id = le64_to_cpu(req->VolatileFileId);
 
-	if (le16_to_cpu(req->DataOffset) ==
-	    (offsetof(struct smb2_write_req, Buffer) - 4)) {
-		data_buf = (char *)&req->Buffer[0];
-	} else {
-		if ((u64)le16_to_cpu(req->DataOffset) + length > get_rfc1002_len(req)) {
-			pr_err("invalid write data offset %u, smb_len %u\n",
-			       le16_to_cpu(req->DataOffset),
-			       get_rfc1002_len(req));
-			err = -EINVAL;
-			goto out;
-		}
-
-		data_buf = (char *)(((char *)&req->hdr.ProtocolId) +
-				le16_to_cpu(req->DataOffset));
+	if ((u64)le16_to_cpu(req->DataOffset) + length > get_rfc1002_len(req)) {
+		pr_err("invalid write data offset %u, smb_len %u\n",
+		       le16_to_cpu(req->DataOffset),
+		       get_rfc1002_len(req));
+		err = -EINVAL;
+		goto out;
 	}
 
+	data_buf = (char *)(((char *)&req->hdr.ProtocolId) +
+			le16_to_cpu(req->DataOffset));
+
 	rpc_resp = ksmbd_rpc_write(work->sess, id, data_buf, length);
 	if (rpc_resp) {
 		if (rpc_resp->flags == KSMBD_RPC_ENOTIMPLEMENTED) {
@@ -6479,20 +6474,15 @@ int smb2_write(struct ksmbd_work *work)
 
 	if (req->Channel != SMB2_CHANNEL_RDMA_V1 &&
 	    req->Channel != SMB2_CHANNEL_RDMA_V1_INVALIDATE) {
-		if (le16_to_cpu(req->DataOffset) ==
-		    (offsetof(struct smb2_write_req, Buffer) - 4)) {
-			data_buf = (char *)&req->Buffer[0];
-		} else {
-			if (le16_to_cpu(req->DataOffset) <
-			    offsetof(struct smb2_write_req, Buffer)) {
-				err = -EINVAL;
-				goto out;
-			}
-
-			data_buf = (char *)(((char *)&req->hdr.ProtocolId) +
-					le16_to_cpu(req->DataOffset));
+		if (le16_to_cpu(req->DataOffset) <
+		    offsetof(struct smb2_write_req, Buffer)) {
+			err = -EINVAL;
+			goto out;
 		}
 
+		data_buf = (char *)(((char *)&req->hdr.ProtocolId) +
+				le16_to_cpu(req->DataOffset));
+
 		ksmbd_debug(SMB, "flags %u\n", le32_to_cpu(req->Flags));
 		if (le32_to_cpu(req->Flags) & SMB2_WRITEFLAG_WRITE_THROUGH)
 			writethrough = true;
-- 
2.34.1