linux-kernel - Re: [PATCH 1/3] tools: hv: fcopy

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Message-ID: <544658CE.8050704@redhat.com>
Date:	Tue, 21 Oct 2014 14:59:58 +0200
From:	Matej Mužila <mmuzila@...hat.com>
To:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
CC:	kys@...rosoft.com, devel@...uxdriverproject.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] tools: hv: fcopy_daemon: Check buffer limits

> sizeof(__u8) is by definition 1 so it's perhaps surplus ?
Now the size is now determined from the structure definition in
include/uapi/linux/hyperv.h

> - C style comments for coding style
Fixed

> 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@...hat.com>

Check if cpmsg->size is in limits of DATA_FRAGMENT

Signed-off-by: Matej Mužila <mmuzila@...hat.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,
 				cpmsg->offset);

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