[PATCH] ksmbd: validate length in smb2_write()

[PATCH] ksmbd: validate length in smb2_write()

[Marios Makassikis]

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@freebox.fr>
---
 smb2pdu.c | 49 +++++++++++++++++++------------------------------
 1 file changed, 19 insertions(+), 30 deletions(-)

diff --git a/smb2pdu.c b/smb2pdu.c
index 1caf0d4..cd7b4fb 100644
--- a/smb2pdu.c
+++ b/smb2pdu.c
@@ -6408,23 +6408,18 @@ static noinline int smb2_write_pipe(struct ksmbd_work *work)
 	length = le32_to_cpu(req->Length);
 	id = req->VolatileFileId;
 
-	if (le16_to_cpu(req->DataOffset) ==
-	    offsetof(struct smb2_write_req, Buffer)) {
-		data_buf = (char *)&req->Buffer[0];
-	} else {
-		if ((u64)le16_to_cpu(req->DataOffset) + length >
-		    get_rfc1002_len(work->request_buf)) {
-			pr_err("invalid write data offset %u, smb_len %u\n",
-			       le16_to_cpu(req->DataOffset),
-			       get_rfc1002_len(work->request_buf));
-			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(work->request_buf)) {
+		pr_err("invalid write data offset %u, smb_len %u\n",
+		       le16_to_cpu(req->DataOffset),
+		       get_rfc1002_len(work->request_buf));
+		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) {
@@ -6565,22 +6560,16 @@ 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)) {
-			data_buf = (char *)&req->Buffer[0];
-		} else {
-			if ((u64)le16_to_cpu(req->DataOffset) + length >
-			    get_rfc1002_len(work->request_buf)) {
-				pr_err("invalid write data offset %u, smb_len %u\n",
-				       le16_to_cpu(req->DataOffset),
-				       get_rfc1002_len(work->request_buf));
-				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(work->request_buf)) {
+			pr_err("invalid write data offset %u, smb_len %u\n",
+			       le16_to_cpu(req->DataOffset),
+			       get_rfc1002_len(work->request_buf));
+			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)
-- 
2.25.1

Re: [PATCH] ksmbd: validate length in smb2_write()

[Namjae Jeon]

2022-05-04 8:13 GMT+09:00, Marios Makassikis <mmakassikis@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@freebox.fr>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>

> ---
>  smb2pdu.c | 49 +++++++++++++++++++------------------------------
>  1 file changed, 19 insertions(+), 30 deletions(-)
>
> diff --git a/smb2pdu.c b/smb2pdu.c
Can you resend the patch after making it on linux kernel source ?

Thanks!