HID: Bluetooth: hidp: make sure input buffers are big enough

HID core expects the input buffers to be at least of size 4096
(HID_MAX_BUFFER_SIZE). Other sizes will result in buffer-overflows if an
input-report is smaller than advertised. We could, like i2c, compute the
biggest report-size instead of using HID_MAX_BUFFER_SIZE, but this will
blow up if report-descriptors are changed after ->start() has been called.
So lets be safe and just use the biggest buffer we have.

Note that this adds an additional copy to the HIDP input path. If there is
a way to make sure the skb-buf is big enough, we should use that instead.

The best way would be to make hid-core honor the @size argument, though,
that sounds easier than it is. So lets just fix the buffer-overflows for
now and afterwards look for a faster way for all transport drivers.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

2 files changed, 18 insertions, 2 deletions

diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
index 292e619db896..d9fb93451442 100644
--- a/net/bluetooth/hidp/core.c
+++ b/net/bluetooth/hidp/core.c
@@ -430,6 +430,16 @@ static void hidp_del_timer(struct hidp_session *session)
                 del_timer(&session->timer);
 }
 
+static void hidp_process_report(struct hidp_session *session,
+                                int type, const u8 *data, int len, int intr)
+{
+        if (len > HID_MAX_BUFFER_SIZE)
+                len = HID_MAX_BUFFER_SIZE;
+
+        memcpy(session->input_buf, data, len);
+        hid_input_report(session->hid, type, session->input_buf, len, intr);
+}
+
 static void hidp_process_handshake(struct hidp_session *session,
                                         unsigned char param)
 {
@@ -502,7 +512,8 @@ static int hidp_process_data(struct hidp_session *session, struct sk_buff *skb,
                         hidp_input_report(session, skb);
 
                 if (session->hid)
-                        hid_input_report(session->hid, HID_INPUT_REPORT, skb->data, skb->len, 0);
+                        hidp_process_report(session, HID_INPUT_REPORT,
+                                            skb->data, skb->len, 0);
                 break;
 
         case HIDP_DATA_RTYPE_OTHER:
@@ -584,7 +595,8 @@ static void hidp_recv_intr_frame(struct hidp_session *session,
                         hidp_input_report(session, skb);
 
                 if (session->hid) {
-                        hid_input_report(session->hid, HID_INPUT_REPORT, skb->data, skb->len, 1);
+                        hidp_process_report(session, HID_INPUT_REPORT,
+                                            skb->data, skb->len, 1);
                         BT_DBG("report len %d", skb->len);
                 }
         } else {
diff --git a/net/bluetooth/hidp/hidp.h b/net/bluetooth/hidp/hidp.h
index ab5241400cf7..8798492a6e99 100644
--- a/net/bluetooth/hidp/hidp.h
+++ b/net/bluetooth/hidp/hidp.h
@@ -24,6 +24,7 @@
 #define __HIDP_H
 
 #include <linux/types.h>
+#include <linux/hid.h>
 #include <linux/kref.h>
 #include <net/bluetooth/bluetooth.h>
 #include <net/bluetooth/l2cap.h>
@@ -179,6 +180,9 @@ struct hidp_session {
 
         /* Used in hidp_output_raw_report() */
         int output_report_success; /* boolean */
+
+        /* temporary input buffer */
+        u8 input_buf[HID_MAX_BUFFER_SIZE];
 };
 
 /* HIDP init defines */