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Old 08-21-2009, 03:18 PM   #1
Registered: Dec 2005
Distribution: Slackware64 14.2 with AlienBob's KDE5
Posts: 270

Rep: Reputation: 38
New kernel breaks DOSEMU

I upgraded my Slackware 12.2 installations to the new kernel packages. Unfortunately, it breaks DOSEMU. I've read elsewhere that similar problems can come up with WINE but I haven't tried that yet. A workaround is to issue this command as root before running DOSEMU:

sysctl -w vm.mmap_min_addr=0

Of course, this pretty much defeats the purpose of the new kernel, unless you remember to issue this afterwards:

sysctl -w vm.mmap_min_addr=4096
Old 08-21-2009, 08:30 PM   #2
Bruce Hill
HCL Maintainer
Registered: Jun 2003
Location: McCalla, AL, USA
Distribution: Fedora, Gentoo, Ubuntu (all servers at work are openSUSE)
Posts: 6,931

Rep: Reputation: 128Reputation: 128
Maybe check LKML for any traffic on that issue, or some IRC channels
such as #dosemu if there is one. What Pat wrote in Slackware's ChangeLog:
Tue Aug 18 18:50:46 CDT 2009
  Patched kernels and kernel packages for Linux to address
  a bug in proto_ops structures which could allow a user to use the
  kernel sendpage operation to execute arbitrary code in page zero.
  This could allow local users to gain escalated privileges.
  This flaw was discovered by Tavis Ormandy and Julien Tinnes of the
  Google Security Team.
  For more information, see:
  In addition, these kernels change the CONFIG_SECURITY_DEFAULT_MMAP_MIN_ADDR
  kernel config option value to 4096, which should prevent the execution
  of arbitrary code by future NULL dereference bugs that might be found
  in the kernel.  If you are compiling your own kernel, please check this
  option in your .config.  If it is set to =0, you may wish to edit it
  to 4096 (or some other value > 0) and then reconfigure, or the kernel
  will not have default protection against zero page attacks from
is what they did in vanilla source, also:
mingdao@jeremiah:~/kernel/linux-$ grep 'DEFAULT_MMAP_MIN_ADDR' .config
Seems to be some anticipation for further null dereference bugs, from
what I've been reading on LKML.
Old 08-21-2009, 11:51 PM   #3
Registered: May 2007
Posts: 517

Rep: Reputation: 191Reputation: 191
The change reportably breaks 16-bit applications, which are old dos and windows apps.


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