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Bug 156029

Summary: kernel may oops if more than 4k worth of string data returned in /proc/devices
Product: Red Hat Enterprise Linux 2.1 Reporter: Neil Horman <nhorman>
Component: kernelAssignee: Don Howard <dhoward>
Status: CLOSED ERRATA QA Contact: Brian Brock <bbrock>
Severity: medium Docs Contact:
Priority: medium    
Version: 2.1CC: tao
Target Milestone: ---   
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: RHSA-2007-0013 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2007-01-17 10:14:35 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 143573    
Attachments:
Description Flags
patch to add missing length check to /proc/devices file none

Description Neil Horman 2005-04-26 19:00:40 UTC 
Description of problem:
the read routine for /proc/devices is missing a length check routine. 
Consequently, if the number of block and char devices in a system totals more
than 4096 bytes of string data between their names and major/minor numbers, the
read routine will sprintf the data off the end of the page and oops the kernel.
other proc files that are part of proc_misc.c protect against this with a length
check that truncates the file if it goes over a page, but this check is missing
from get_device_list and get_blkdev_list.

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

How reproducible:
always

Steps to Reproduce:
1. register sufficient char/block devices in a system to create > 4096 bytes of
string data for /proc/devices
2. cat /proc/devices
3.
  
Actual results:
system will oops on a page fault

Expected results:
system should truncate file to 4096 bytes.

Additional info:
Comment 1 Neil Horman 2005-04-26 19:00:40 UTC 
Created attachment 113681 [details]
patch to add missing length check to /proc/devices file
Comment 5 Don Howard 2006-09-14 18:14:33 UTC 
Hi Neil -

This ticket fell off my radar.  It looks like the RHEL3 patch applies to 2.1. 
Can you attach a test case for this issue?
Comment 6 Neil Horman 2006-09-14 19:14:30 UTC 
hey don-
   I don't think I have my old test case laying about any more, but suffice it
to say, all you need to do is write a kernel module that calls register_chrdev
for 256 different major/minor combinations, and give each device a name that is
at least 20 characters long.  That will overrun the 4k buffer that is allocated
for /proc/devices and cause an oops.  with the patch the file will be truncated
at 4096 bytes.  

I'll see if I can throw my old test code back together in a little bit.
Comment 7 Don Howard 2006-09-14 19:30:09 UTC 
Thanks for checking, Neil.  Don't worry about re-creating your testcase, I can
do that.
Comment 11 Mike Gahagan 2006-12-19 20:15:38 UTC 
bug reproduced using e.70 and fix verified on e.71.
Comment 13 Red Hat Bugzilla 2007-01-17 10:14:35 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.

http://rhn.redhat.com/errata/RHSA-2007-0013.html