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Bug 628634 - vhost_net: untested error handling in vhost_net_start
Summary: vhost_net: untested error handling in vhost_net_start
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: qemu-kvm
Version: 6.1
Hardware: All
OS: Linux
low
medium
Target Milestone: beta
: ---
Assignee: jason wang
QA Contact: Virtualization Bugs
URL:
Whiteboard:
Depends On:
Blocks: 580954
TreeView+ depends on / blocked
 
Reported: 2010-08-30 15:08 UTC by Jes Sorensen
Modified: 2013-01-09 23:04 UTC (History)
6 users (show)

Fixed In Version: qemu-kvm-0.12.1.2-2.126.el6
Doc Type: Bug Fix
Doc Text:
Cause: bug in the error handling code of vhost, check whether an unsigned value is greater than zero would make the result always true. Consequence: qemu-kvm would hang when it met errors when start a vhost_net backend. Fix: Fix the error handling code. Result: qemu-kvm would never hang when it fails to start vhost_net backend.
Clone Of:
Environment:
Last Closed: 2011-05-19 11:33:09 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2011:0534 0 normal SHIPPED_LIVE Important: qemu-kvm security, bug fix, and enhancement update 2011-05-19 11:20:36 UTC

Description Jes Sorensen 2010-08-30 15:08:51 UTC 
Description of problem:
hw/vhost_net.c:vhost_net_start() seems to have untested error handling.

The code looks like this:

int vhost_net_start(struct vhost_net *net,
                    VirtIODevice *dev)
{
    struct vhost_vring_file file = { };
 ...
    for (file.index = 0; file.index < net->dev.nvqs; ++file.index) {
        r = ioctl(net->dev.control, VHOST_NET_SET_BACKEND, &file);
        if (r < 0) {
            r = -errno;
            goto fail;
        }
    }
    return 0;
fail:
    file.fd = -1;
    while (--file.index >= 0) {
        int r = ioctl(net->dev.control, VHOST_NET_SET_BACKEND, &file);
        assert(r >= 0);
    }

As file.index is an unsigned integer, the while() loop will
always be true, so in case of error we will exit on an assert
or loop forever.

This is present in both RHEL6 and upstream QEMU.

It is not obvious to me what the code was intended to do here,
so please have a look.


Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
1.
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Actual results:


Expected results:


Additional info:
Comment 2 Jes Sorensen 2010-09-14 11:52:33 UTC 
Taking as I have a fix.
Comment 3 Jes Sorensen 2010-09-14 12:00:58 UTC 
Ok back to Michael as he has a different fix.
Comment 4 Glauber Costa 2010-11-04 15:46:06 UTC 
How is it going upstream?

Also, how important it is to have it in 6.1?
Comment 5 jason wang 2010-11-19 02:20:42 UTC 
The fix have already in upstream, just need to be backported in 6.1
Comment 11 jason wang 2011-05-05 10:04:03 UTC 
    Technical note added. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    New Contents:
Cause: bug in the error handling code of vhost, check whether an unsigned value is greater than zero would make the result always true.

Consequence: qemu-kvm would hang when it met errors when start a vhost_net backend.

Fix: Fix the error handling code.

Result: qemu-kvm would never hang when it fails to start vhost_net backend.
Comment 12 errata-xmlrpc 2011-05-19 11:33:09 UTC 
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHSA-2011-0534.html
Comment 13 errata-xmlrpc 2011-05-19 12:47:57 UTC 
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHSA-2011-0534.html
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