ksmbd: fix Out-of-Bounds Read in ksmbd_vfs_stream_read

An offset from client could be a negative value, It could lead
to an out-of-bounds read from the stream_buf.
Note that this issue is coming when setting
'vfs objects = streams_xattr parameter' in ksmbd.conf.

Cc: [email protected] # v5.15+
Reported-by: Jordy Zomer <[email protected]>
Signed-off-by: Jordy Zomer <[email protected]>
Signed-off-by: Namjae Jeon <[email protected]>
Signed-off-by: Steve French <[email protected]>

Author: JordyZomer

fs/smb/server/smb2pdu.c

@@ -6663,6 +6663,10 @@ int smb2_read(struct ksmbd_work *work)
 	}
 
 	offset = le64_to_cpu(req->Offset);
+	if (offset < 0) {
+		err = -EINVAL;
+		goto out;
+	}
 	length = le32_to_cpu(req->Length);
 	mincount = le32_to_cpu(req->MinimumCount);