mmap occasionally infringes on stack

This document (7004855) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 11
SUSE Linux Enterprise Server 10 Service Pack 2
SUSE Linux Enterprise Server 10 Service Pack 3

Situation

The Linux kernel has a flaw that can potentially cause memory mappings
created by a given process to silently overlap with its stack address space.
This can cause silent corruption of the data that belongs to the affected process.

The problem is relevant only in the case when randomised address
space is enabled, which is the default behaviour on SLES.

The problem is specific to the x86_64 architecture, and it has been
verified that it affects:

- SUSE Linux Enterprise Server 11 (SLES11) kernel release 2.6.27.25-0.1
and
- SLES11, kernel release 2.6.27.29-0.1

The problem has not been reproduced on older SLES11 kernel
releases, SLES10SP2, or SLES10SP3 kernels but it's likely that they're
equally affected.

Resolution

Problem is resolved in

SLES11 kernel update 2.6.27.37-0.1.1.
SLES10 SP2 kernel update 2.6.16.60-0.42.7
SLES10 SP3 kernel update 2.6.16.60-0.57.1.

Additional Information

In the rare cases where a kernelupdate is not an option, a workaround is to disable randomisation.

- Either at boot time by adding the kernel boot parameter
"norandmaps" to the kernel boot command line.

- Or via sysctl:

- add the following line to the /etc/sysctl.conf file
kernel.randomize_va_space = 0

- run sysctl -p for the change to take effect.

Disclaimer

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