# scanmem/ptrace causes total system freeze

## m_a_xim

Hi,

Linux just hanged on me, although it may have been Xorg. Everything just froze and no combination of keys would make any difference (ctrl-alt-f[1-6], ctrl-alt-syst-k,...). I was forced to hard reboot. 

I was playing a video game (GTA SA on wine 1.1.35) with wine and I decided to use the scanmem utility to try and cheat (it scans and modifies the memory with ptrace). I managed to isolate a variable in memory and I instructed scanmem to set it to zero every second but after a few seconds the whole system just froze. The worst is that none of this was done as root.

This error happens randomly when setting the variable (about 10% of the time : the freeze will usually occur around 10 seconds after after I enable the cheat).

The same thing happens when I try scanmem on pSX (Playstation emulator). 

Any idea what I could do?

Kernel: 2.6.31-gentoo-r6 (amd64)

CPU: AMD Athlon(tm) 64 X2 Dual Core Processor 5600+

GPU: VGA compatible controller: ATI Technologies Inc RV610 video device [Radeon HD 2400 PRO]

Graphics driver: ati-drivers-9.11 (fglrx)

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## Hu

Is the hang reproducible with an untainted kernel?

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## m_a_xim

What do you mean by 'untainted'? If you want, I'll try to reproduce it with Ubuntu 9.04 that I already have installed.

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## m_a_xim

Same bug with Ubuntu 9.04 amd64!

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## Hu

Your kernel has been tainted by loading a proprietary driver.  Please configure that driver not to autoload, reboot, verify your kernel is untainted, and then reproduce the problem.

Encountering the problem with Ubuntu is not definitive, since it is possible that you tainted that kernel, too.

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## m_a_xim

You're right. with the open-source ATI drivers, I don't have this problem. But the frame-rate is totally unplayable! 

Maybe I can file a bug to AMD.

Thanks for your help.

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