Bug 441390 - Memory corruption due to VNIF increase
Summary: Memory corruption due to VNIF increase
Alias: None
Product: Red Hat Enterprise Linux 5
Classification: Red Hat
Component: kernel-xen   
(Show other bugs)
Version: 5.2
Hardware: All
OS: Linux
Target Milestone: rc
: ---
Assignee: Tetsu Yamamoto
QA Contact: Martin Jenner
: 433755 (view as bug list)
Depends On:
Blocks: 442298
TreeView+ depends on / blocked
Reported: 2008-04-07 20:23 UTC by Bill Burns
Modified: 2008-05-21 15:13 UTC (History)
3 users (show)

Fixed In Version: RHBA-2008-0314
Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of:
Last Closed: 2008-05-21 15:13:59 UTC
Type: ---
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

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External Trackers
Tracker ID Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2008:0314 normal SHIPPED_LIVE Updated kernel packages for Red Hat Enterprise Linux 5.2 2008-05-20 18:43:34 UTC

Description Bill Burns 2008-04-07 20:23:56 UTC
The change to increase the VNIF's allowed per guest introduced an error that can
cause memory corruption. Detail follows:

A PV OS has two grant table data structures: the grant table itself and a free 
list.  The free list is composed of an array of pages, which grow dynamically as 
the guest OS requires more grants.  While the grant table contains 8-byte 
entries, the free list contains 4-byte entries.  So we have half as many pages 
in the free list than in the grant table.

There was a bug in the free list allocation code. The free list was indexed as 
if it was the same size as the grant table.  But it's only half as large.  So 
memory got corrupted, and I was seeing crashes in the slab allocator later on.

A patch has been posted upstream.

Comment 2 Mark McLoughlin 2008-04-08 12:17:39 UTC
Some details on this:

 - bug #297331 and bug #223908 were the original bugs requesting that guests
   be able to have more than 3 VNIFs

 - The upstream fix we backported was:


 - This bug is about a potential memory corruption bug with the original patch.
   We have not yet reproduced this memory corruption, but the fix is upstream
   in linux-2.6.18-xen.hg and linus's tree:


Comment 5 Don Zickus 2008-04-09 18:44:53 UTC
in kernel-2.6.18-89.el5
You can download this test kernel from http://people.redhat.com/dzickus/el5

Comment 7 Bill Burns 2008-04-16 11:59:57 UTC
*** Bug 433755 has been marked as a duplicate of this bug. ***

Comment 9 errata-xmlrpc 2008-05-21 15:13:59 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 the 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.


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