Re: [syzbot] [hfs?] WARNING in hfs_write_inode

[Dmitry Vyukov]

On Thu, 5 Jan 2023 at 17:45, Viacheslav Dubeyko <slava@xxxxxxxxxxx> wrote:
> > On Wed, Jan 04, 2023 at 08:37:16PM -0800, Viacheslav Dubeyko wrote:
> >> Also, as far as I can see, available volume in report (mount_0.gz) somehow corrupted already:
> >
> > Syzbot generates deliberately-corrupted (aka fuzzed) filesystem images.
> > So basically, you can't trust anything you read from the disc.
> >
>
> If the volume has been deliberately corrupted, then no guarantee that file system
> driver will behave nicely. Technically speaking, inode write operation should never
> happened for corrupted volume because the corruption should be detected during
> b-tree node initialization time. If we would like to achieve such nice state of HFS/HFS+
> drivers, then it requires a lot of refactoring/implementation efforts. I am not sure that
> it is worth to do because not so many guys really use HFS/HFS+ as the main file
> system under Linux.


Most popular distros will happily auto-mount HFS/HFS+ from anything
inserted into USB (e.g. what one may think is a charger). This creates
interesting security consequences for most Linux users.
An image may also be corrupted non-deliberately, which will lead to
random memory corruptions if the kernel trusts it blindly.