Messages in this thread | | | Date | Wed, 21 Feb 2018 12:36:36 +1100 | From | Dave Chinner <> | Subject | Re: [RFC PATCH v16 0/6] mm: security: ro protection for dynamic data |
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On Tue, Feb 20, 2018 at 03:56:00PM -0800, Matthew Wilcox wrote: > On Wed, Feb 21, 2018 at 08:36:04AM +1100, Dave Chinner wrote: > > FWIW, I'm not wanting to use it to replace static variables. All the > > structures are dynamically allocated right now, and get assigned to > > other dynamically allocated pointers. I'd likely split the current > > structures into a "ro after init" structure and rw structure, so > > how does the "__ro_after_init" attribute work in that case? Is it > > something like this? > > > > struct xfs_mount { > > struct xfs_mount_ro{ > > ....... > > } *ro __ro_after_init; ^^^^^^^^
pointer, not embedded structure....
> > ...... > > No, you'd do: > > struct xfs_mount_ro { > [...] > }; > > struct xfs_mount { > const struct xfs_mount_ro *ro; > [...] > };
.... so that's pretty much the same thing :P
> > Also, what compile time checks are in place to catch writes to > > ro structure members? Is sparse going to be able to check this sort > > of thing, like is does with endian-specific variables? > > Just labelling the pointer const should be enough for the compiler to > catch unintended writes.
Ok.
> > > I'd be interested to have your review of the pmalloc API, if you think > > > something is missing, once I send out the next revision. > > > > I'll look at it in more depth when it comes past again. :P > > I think the key question is whether you want a slab-style interface > or whether you want a kmalloc-style interface. I'd been assuming > the former, but Igor has implemented the latter already.
Slabs are rally only useful when you have lots of a specific type of object. I'm concerned mostly about one-off per-mount point structures, of which there are relatively few. A heap-like pool per mount is fine for this.
Cheers,
Dave. -- Dave Chinner dchinner@redhat.com
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