Re: [PATCH] First patch to improve ELF sanity checks

[Davide Libenzi]

On Sat, 10 Jan 2004, Jesper Juhl wrote:

> 
> Hi,
> 
> Andrew, please consider including the patch below in -mm for testing.
> The patch works nicely here, but broader testing and review would be good.
> An explanation of the patch can be found below.
> 
> This is only a first version, and it does not yet check all I want it to,
> but the checks it does add should be valid. As far as I've been able to
> tell, the checks it makes are valid according to the ELF spec, and it does
> not seem to break anything. I'm currently using it on my own box and I
> have not yet seen a single binary fail to load - I've also been testing by
> modifying a valid ELF binary to contain invalid info in the fields that
> are checked, and all my test-cases fail as expected.
> 
> This patch /should/ work on all archs. It adds a check to asm-i386/elf.h
> that I've not added to any other archs for the simple reason that I don't
> know what a valid check would be on anything but x86 32 bit atm, but I'll
> be looking into that, and the additional check for i386 should not harm
> other archs - their checking will just be a little weaker than i386.
> 
> So far I've only added these checks to load_elf_binary , but Jakub pointed
> out to me that they would need to go into load_elf_interp as well. I will
> add the checks there as well as soon as I convince myself that they really
> are needed there. So far I only see load_elf_binary calling
> load_elf_interp, and since load_elf_binary does the checks and abort if
> they fail before calling load_elf_interp I don't (yet) see why they would
> be needed there as well. I'm sure Jakub is probably right, and I'm looking

You do not have to convince yourself, trust Jakub ;) The checks are needed 
even inside load_elf_interp since they refer to two different images. You 
might also want to create a separate function that does the checks and 
call it from both load_elf_interp and load_elf_binary.



- Davide





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