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

[Michael Chang]

I have to resend the mail as the attached kernel image is too big that may not
reach the list eventually. Sorry if you get duplicated mail. 

If you still have problem with reproducing the problem please let me know. I
could provide download link for the kernel file.

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.

> 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.

> 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