[PATCH 1/3] tools: hv: fcopy_daemon: Check buffer limits

[Matej Mužila]

From: Matej Mužila <mmuzila@xxxxxxxxxx>

Check if cpmsg->size is in limits of DATA_FRAGMENT

Signed-off-by: Matej Mužila <mmuzila@xxxxxxxxxx>
Acked-by:  K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
---
If corrupted data are read from /dev/vmbus/hv_fcopy, pwrite can
read from memory outside of the buffer (defined at line 138).
Added check. 
---
@@ -104,6 +104,10 @@ static int hv_copy_data(struct hv_do_fcopy *cpmsg)
 {
 	ssize_t bytes_written;
 
+	// Check if the cpmsg->size is in limits of DATA_FRAGMENT
+	if (cpmsg->size > DATA_FRAGMENT * sizeof(__u8))
+		return HV_E_FAIL;
+
 	bytes_written = pwrite(target_fd, cpmsg->data, cpmsg->size,
 				cpmsg->offset);

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