Re: [PATCH v2] grub-file: fix segmentation fault

[Andrei Borzenkov]

22.11.2016 10:10, Michael Chang пишет:
> On Fri, Nov 18, 2016 at 11:50:25AM +0300, Andrei Borzenkov wrote:
>> Hmm ... I must admit I am confused how we can get NULL here. Filters
>> are called after primary file->name is set and each filter copies
>> previous struct file, which means returned file will inherit pointer
>> to the same file name.
> 
> No. I don't think so. Looking into gzio or xzio file filters they did not copy
> original handle to new allocated one. And the new handle gets initialized
> without file->name being set from original one. The new handle then returned
> to upper file layer with file->name being null.
> 

Right, I was mistaken.

>> Anyway, exactly because filters themselves do not free file->name this
>> patch means memory leak.
> 
> Same reason above, as long as the filters did not allocate it, they did not
> need to free.
> 

Yes, but your patch allocates copy of name and (some) filters set it to
NULL so it is leaked.

What about attached patch? It does not increase size of kernel.

I am not thrilled as it does require more discipline from filter author.
OTOH we may find some way to consolidate boilerplate later.

@Dann, this also solves your concerns about layering violation in
progress module as side effect. Could you test this patch? Thank you!

>> Michael, could you provide reproducer for it?
> 
> I can still reproduce the segfault on latest git HEAD. Here is kernel image
> attached to reproduce the problem with:
> 
>  grub/build-xen # ./grub-file --is-x86_64-xen-domu 
> /boot/vmlinux-4.8.4-1-default.gz
>  Segmentation fault (core dumped)
> 
> Thanks,
> Michael
>

file-filter-filename.patch
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