Re: [PATCH] fat: Support fallocate on fat.

OGAWA Hirofumi
2012-07-09T10:56:00Z

>>> + /*
>>> + * calculate i_blocks and mmu_private from the actual number of
>>> + * allocated clusters instead of doing it from file size.This ensures
>>> + * that the preallocated disk space using FALLOC_FL_KEEP_SIZE is
>>> + * persistent across remounts and writes go into the allocated
>>> clusters.
>>> + */
>>> + fat_calc_dir_size(inode);
>>
>> Looks like the wrong. If you didn't initialize preallocated space, the
>> data never be exposed to userland. It is security bug.
> As explained above, if we do append write instead of seeking into a
> random offset, there is no security risk.

So it means? - if we didn't, there is.

> The main disadvantage with initializing the preallocated space (as is
> done in case of without FALLOC_FL_KEEP_SIZE ) is it takes long time
> for bigger allocation sizes. It took ~70 seconds to preallocate 2GB on
> our target if FALLOC_FL_KEEP_SIZE is not set.

It doesn't become the reason to expose uninitialized data.

Thanks.