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Bug 1070249 - Permission denied on audio devices when there is a tty device with a long name
Summary: Permission denied on audio devices when there is a tty device with a long name
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: ConsoleKit
Version: 6.5
Hardware: All
OS: Linux
unspecified
medium
Target Milestone: rc
: ---
Assignee: Michal Sekletar
QA Contact: Frantisek Sumsal
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2014-02-26 13:37 UTC by James Pearson
Modified: 2016-05-11 00:58 UTC (History)
2 users (show)

Fixed In Version: ConsoleKit-0.4.1-4.el6
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2016-05-11 00:58:57 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)
Simple patch to increase tty device name buffer length (325 bytes, patch)
2014-02-26 13:37 UTC, James Pearson 		no flags Details | Diff
View All


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2016:0942 0 normal SHIPPED_LIVE ConsoleKit bug fix update 2016-11-24 23:09:27 UTC

Description James Pearson 2014-02-26 13:37:48 UTC 
Created attachment 868025 [details]
Simple patch to increase tty device name buffer length

Description of problem:

ConsoleKit fails to add the username to /dev/snd/* ACLs on login when there is a tty device with a name longer than 16 characters - hence any audio tool used by the user when logged in on the console give errors like:

ALSA lib pulse.c:229:(pulse_connect) PulseAudio: Unable to connect: Connection refused

The long tty device name (in this case) is created when a third party kernel module is loaded

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

ConsoleKit-0.4.1-3.el6

How reproducible:

Always

Steps to Reproduce:
1. load third party kernel module that creates a tty device with a name longer than 16 characters
2. login on the console
3. try to use anything that uses audio

Actual results:

Username of console user not added to the ACLs for sound device files /dev/snd/*

Unable to use use audio

Expected results:

Username of console user added to the ACLs for sound device files /dev/snd/*

Able to use use audio

Additional info:

The utility 'ck-collect-session-info' crashes with a 'buffer overflow detected' error - so console-kit is unable to set the ACLs on the sound devices

The 'name' char array in struct tty_map_node defined in ck-sysdeps-linux.c is only 16 characters - so tty device names longer than this overflow this buffer

A simple fix is to increase the size of this buffer - a better fix would be to dynamically allocate a buffer of the correct length at runtime
Comment 5 Michal Sekletar 2016-01-19 08:35:57 UTC 
I overlooked your attachment and merged a bit different patch which bumps the length to 32. Then I checked Debian and found out that they ship the same patch as well, so I guess 32 should be fine.
Comment 6 James Pearson 2016-01-19 10:33:15 UTC 
32 will be fine in our case - although I guess it should really match whatever limit the kernel allows for tty device names
Comment 7 Frantisek Sumsal 2016-03-04 17:54:59 UTC 
1) Reproducer
## Find some process running on tty* (it doesn't matter which one)
# ps aux | grep tty
## Save its pid
## Run ck-collect-session-info in gdb and replace device buffer with specially crafted tty name
# gdb --args /usr/libexec/ck-collect-session-info --uid 0 --pid 1473
(gdb) break ck-sysdeps-linux.c:122
(gdb) run
(gdb) set var buf=" /dev/ttywithaverylongname0 "
(gdb) cont

2) Output
a) Old package
<...>
(gdb) set var buf=" /dev/ttywithaverylongname0 "
(gdb) p buf
$1 = " /dev/ttywithaverylongname0 ", '\000' <repeats 9971 times>
(gdb) cont
Continuing.
*** buffer overflow detected ***: /usr/libexec/ck-collect-session-info terminated
======= Backtrace: =========
/lib64/libc.so.6(__fortify_fail+0x37)[0x7ffff74f66d7]
<...>
Program received signal SIGABRT, Aborted.
0x00007ffff74265e5 in raise () from /lib64/libc.so.6

b) New package
<...>
(gdb) set var buf=" /dev/ttywithaverylongname0 "
(gdb) p buf
$1 = " /dev/ttywithaverylongname0 ", '\000' <repeats 9971 times>
(gdb) cont
Continuing.
unix-user = 0
display-device = /dev/tty1
login-session-id = 4294967295

Program exited normally.
Comment 9 errata-xmlrpc 2016-05-11 00:58:57 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2016-0942.html
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