Null bytes in files access by 2 or more NFS clients
Bug #199037 reported by
Timo Aaltonen
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
linux (Fedora) |
Fix Released
|
High
|
|||
linux (Ubuntu) |
Fix Released
|
High
|
Ben Collins |
Bug Description
There's a bug in the linux NFS client where it's possible to corrupt files when the server is a NetApp filer and two (or more) clients have write access to the file. A good example of such a file is ~/.zhistory. This has been fixed upstream and on RHEL5:
http://
and discussed here:
https:/
Please apply to the Hardy kernel, and possibly others, thanks!
description: | updated |
Changed in linux: | |
milestone: | none → ubuntu-8.04-beta |
Changed in linux: | |
status: | Unknown → Invalid |
Changed in linux: | |
status: | Invalid → Fix Committed |
Changed in linux: | |
status: | Fix Committed → Fix Released |
Changed in linux (Fedora): | |
importance: | Unknown → High |
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From Bugzilla Helper:
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.11) Gecko/20071127 Firefox/2.0.0.11
Description of problem:
CommuniGate Systems is reporting this case on behalf of two CommuniGate/RedHat customers running RedHat Enterprise Server 5.1 and seeing some problems related to file integrity on this platform. We have two customers who upgraded their CommuniGate Pro cluster nodes to RedHat 5.1, from an earlier RHES 4.1 version. In both these cases, the kernel reportedly in use is this: 2.6.18-53.el5
We also have reports of a possibly identical problem with a customer running this kernel version, though we don't have the specifics of the Linux OS version: kernel version 2.6.18-8.1.8
In both of these cases, the customers began to get what appear to be
"null bytes" in mailboxes. I will a screenshot png of one of
these mailboxes, as seen with vi.
The mount options used are: 32768,wsize= 32768,hard, intr,timeo= 600,bg, retrans= 2,noatime
tcp,rsize=
The output of "mount -v" for one of these customers showed the following: 30.35.5: /vol/CGPweb on /CGPweb type nfs nfsvers= 3,proto= tcp,rsize= 32768,wsize= 32768,timeo= 600,hard, intr,bg, acregmax= 6,addr= 172.30. 35.5)
>>>172.
>>>(rw,
The exact operating system in use was:
>>>Linux MSA 2.6.18-53.el5 #1 SMP Wed Oct 10 16:34:02 EDT 2007 i686 i686 i386 GNU/Linux Red Hat Enterprise Linux 5.
When I last researched this in detail, it appeared that the byte offsets
and total sizes were still correct after the null bytes were inserted;
only the contents of those bytes were replaced with null characters. So,
it appeared at first glance that it was a 1:1 replacement of valid data
with "corruption"-type data of some sort.
When analyzing CommuniGate Pro logs (which report the file sizes and offsets of all messages), we found two types of symptoms:
1. a missing message with null bytes inserted instead (1:1 replacement of characters bytes into NULL bytes)
2. no missing message, but null bytes between/within two messages, and there is some indication that parts of some messages are missing (and replaced with NULL bytes)
A key question that is not 100% clearly answered is whether there is any indication of additional bytes ever being added, or if the null bytes are simply byte-replacement of data. From the available evidence, it appears that there is just 1:1 byte replacement.
Also, shile this is not 100% confirmed - CommuniGate Pro appears to be getting the correct byte offsets from the file system, as noted in the "math" parts of this document. This would suggest a problem that is different than the previous pre-2.6.13 Linux NFS kernel problem. Also, the time interval between some of the events that insert null bytes is rather large, often times 10+ minutes of interval between events.
Of these two customers, both went back to RedHat 4.5, and the problem
immediately disappeared. We have many customers running RedHat ES 4.5 successfully. Earlier RedHat versions than this still have a different NFS kernel bug which can cause serious problems in an CommuniGate Pro Dynamic Cluster when NFS-based. (A few years ago, we discovered a Linux
kernel bug related to NFS client handling in the kernel (s...