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Bugtraq: Re: Hot fix for do_brk bug

From: Mariusz Woloszyn (emsi_at_ipartners.pl)
Date: Dec 09 2003


On Sat, 6 Dec 2003, Pavel harry_x Palát wrote:

> > It would be less intrusive to the kernel to supply a fixed do_brk()
> > and replace the do_brk with a jump to your version.
>
> I've written similar patch few days ago. The patch only modifies first
> instructions of do_brk() (it replaces them with jmp to function in LKM.
> It can be downloaded from http://wizard.ath.cx/fixbrk.tar.gz
>
> But beware, I wrote it in rush and it's pretty odly written :-) But it
> worked on my two servers (both were running 2.4.21 kernel with grsecurity
> patch).
>

Sometimes it might be valuable to patch your fixbrk.pl.
Your version does:

system("gcc -D__KERNEL__ -DMODULE -c -o _fixbrk.o fixbrk.c");

On some hosts, to compile this module you need to specify the path to
kernel header files. For example:

system("gcc -D__KERNEL__ -DMODULE -I/usr/src/linux/include -c -o _fixbrk.o
fixbrk.c");

Otherwise you might end up with something like:

/usr/include/asm/processor.h:56: error: `CONFIG_X86_L1_CACHE_SHIFT' undeclared here (not in a function)

Regards,

-- 
Mariusz Wo³oszyn
Internet Security Specialist, GTS - Internet Partners

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