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

Matej Mužila mmuzila at redhat.com
Tue Oct 21 12:59:58 UTC 2014

> sizeof(__u8) is by definition 1 so it's perhaps surplus ?
Now the size is now determined from the structure definition in

> - C style comments for coding style

> Also your patch block is devoid of a few thins like the file name...
I'm sorry, the (missing) filename mistake occured in copy-paste process.

Here is the patch as it (I hope) should look like:
From: Matej Mužila <mmuzila at redhat.com>

Check if cpmsg->size is in limits of DATA_FRAGMENT

Signed-off-by: Matej Mužila <mmuzila at redhat.com>
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. 
diff --git a/tools/hv/hv_fcopy_daemon.c b/tools/hv/hv_fcopy_daemon.c
index 6f27e2f..1fc2dc2 100644
--- a/tools/hv/hv_fcopy_daemon.c
+++ b/tools/hv/hv_fcopy_daemon.c
@@ -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 > sizeof(cpmsg->data)) 
+		return HV_E_FAIL;
 	bytes_written = pwrite(target_fd, cpmsg->data, cpmsg->size,

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