Re: [RFC 6/6] Revert "pstore/ram_core: Do not reset restored zone's position and size"

From: Joel Fernandes
Date: Fri Oct 26 2018 - 14:22:24 EST

On Fri, Oct 26, 2018 at 07:16:28PM +0100, Kees Cook wrote:
> On Fri, Oct 26, 2018 at 7:00 PM, Joel Fernandes (Google)
> <joel@xxxxxxxxxxxxxxxxx> wrote:
> > This reverts commit 25b63da64708212985c06c7f8b089d356efdd9cf.
> >
> > Due to the commit which is being reverted here, it is not possible to
> > know if pstore's messages were from a previous boot, or from very old
> > boots. This creates an awkard situation where its unclear if crash or
> > other logs are from the previous boot or from very old boots. Also
> > typically we dump the pstore buffers after one reboot and are interested
> > in only the previous boot's crash so let us reset the buffer after we
> > save them.
> >
> > Lastly, if we don't zap them, then I think it is possible that part of
> > the buffer will be from this boot and the other parts will be from
> > previous boots. So this revert fixes all of this by calling
> > persistent_ram_zap always.
> I like the other patches (comments coming), but not this one: it's
> very intentional to keep all crashes around until they're explicitly
> unlinked from the pstore filesystem from userspace. Especially true
> for catching chains of kernel crashes, or a failed log collection,
> etc. Surviving multiple reboots is the expected behavior on Chrome OS
> too.

Oh, ok. Hence the RFC tag ;-) We can drop this one then. I forgot that
unlinking was another way to clear the logs.


- Joel