New subject: [Bug 12548] New default for /proc/sys/vm/ mmap_min_addr clashing with wine preloader

13 Apr 2008


      http://bugs.winehq.org/show_bug.cgi?id=12548
Summary: New default for /proc/sys/vm/mmap_min_addr clashing with
                    wine preloader
           Product: Wine
           Version: CVS/GIT
          Platform: Other
               URL: https://launchpad.net/bugs/114025
        OS/Version: other
            Status: NEW
          Severity: normal
          Priority: P2
         Component: loader
        AssignedTo: wine-bugs@winehq.org
        ReportedBy: dank@kegel.com
The problem
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-0600
prompted distributions to raise the default for /proc/sys/vm/mmap_min_addr
or even DEFAULT_MMAP_MIN_ADDR to 64K from 0.  
This causes the following error message when starting (some?) wine apps:
  Problem with wine preloader: Warning: failed to reserve range
00000000-60000000
See discussion:
https://launchpad.net/bugs/114025
http://kerneltrap.org/Linux/Patching_CVE-2008-0600_Local_Root_Exploit
http://kerneltrap.org/Linux/2.4.36_Stable_Release
You can check to see if you're on an affected system
by doing "cat /proc/sys/vm/mmap_min".  If that succeeds, and its value 
is nonzero, you're probably running into this.
To work around the problem temporarily, you can change this value
with the command
 sudo sysctl -w vm.mmap_min_addr=0
but that value gets reset at boot.  To work around the problem more
persistantly, also edit the file /etc/sysctl.conf like this:
# protect bottom 64k of memory from mmap to prevent NULL-dereference
 # attacks against potential future kernel security vulnerabilities.
 # (Added in kernel 2.6.23.)
-vm.mmap_min_addr = 65536
+vm.mmap_min_addr = 0
http://kerneltrap.org/Linux/2.4.36_Stable_Release suggests using
a value of 4096 for this.
"Advanced Windows", 3rd edition, says that the memory area 0 to 4095
is not mapped anyway in windows (it's a guard page).
So maybe when Wine is installed, we could somehow change that value
to 4096, and have Wine's preloader happily continue if it can't
map the bottom page of RAM.
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[Bug 12548] New: New default for /proc/sys/vm/ mmap_min_addr clashing with wine preloader