[PATCH] usb: gadget: f_uac1_legacy: validate control request size

[Taegu Ha <hataegu0826@gmail.com>]

f_audio_complete() copies req->length bytes into a 4-byte stack
variable:

  u32 data = 0;
  memcpy(&data, req->buf, req->length);

req->length is derived from the host-controlled USB request path,
which can lead to a stack out-of-bounds write.

Validate req->actual against the expected payload size for the
supported control selectors and decode only the expected amount
of data.

This avoids copying a host-influenced length into a fixed-size
stack object.

Signed-off-by: Taegu Ha <hataegu0826@gmail.com>
---
 drivers/usb/gadget/function/f_uac1_legacy.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/gadget/function/f_uac1_legacy.c b/drivers/usb/gadget/function/f_uac1_legacy.c
index a0c953a99727..6d6fe5db99f5 100644
--- a/drivers/usb/gadget/function/f_uac1_legacy.c
+++ b/drivers/usb/gadget/function/f_uac1_legacy.c
@@ -11,6 +11,7 @@
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/atomic.h>
+#include <asm/unaligned.h>
 
 #include "u_uac1_legacy.h"
 
@@ -370,9 +371,21 @@ static void f_audio_complete(struct usb_ep *ep, struct usb_request *req)
 		if (ep == out_ep)
 			f_audio_out_ep_complete(ep, req);
 		else if (audio->set_con) {
-			memcpy(&data, req->buf, req->length);
-			audio->set_con->set(audio->set_con, audio->set_cmd,
-					le16_to_cpu(data));
+			struct usb_audio_control *con = audio->set_con;
+
+			if ((con->type == UAC_FU_MUTE && req->actual != sizeof(u8)) ||
+				(con->type == UAC_FU_VOLUME && req->actual != sizeof(__le16)) ||
+				(con->type != UAC_FU_MUTE && con->type != UAC_FU_VOLUME)) {
+				usb_ep_set_halt(ep);
+				audio->set_con = NULL;
+				break;
+			}
+
+			if (con->type == UAC_FU_MUTE)
+				data = *(u8 *)req->buf;
+			else
+				data = get_unaligned_le16(req->buf);
+			con->set(con, audio->set_cmd, data);
 			audio->set_con = NULL;
 		}
 		break;
-- 
2.43.0