On Tue, May 12, 2020 at 11:55:20AM +0800, WeiXiong Liao wrote:
> On 2020/5/12 AM 7:32, Kees Cook wrote:
> > [...]
> > +struct psz_context {
> > + struct pstore_zone **kpszs;
> > + unsigned int kmsg_max_cnt;
> > + unsigned int kmsg_read_cnt;
> > + unsigned int kmsg_write_cnt;
> > + /*
> > + * These counters should be calculated during recovery.
> > + * It records the oops/panic times after crashes rather than boots.
> > + */
> > + unsigned int oops_counter;
> > + unsigned int panic_counter;
>
> oops/panic_counter is designed to count the crash times since the
> linux kernel was installed. pstore/zone lookup the max counter from all
> valid kmsg zones when recovery and saves them to oops/panic_counter.
> However, they are unable to get real number if we remove files. It's
> not serious, we can fix it after this series.
Since the kernel was installed? I don't see a kernel version check in
here? Or do you mean "since ever", in that it's a rolling count?
> And since pstore supports "max_reason", should pstore/zone count for
> other reason?
For now, no. I opted to try to keep this as simple as possible a port
from dump_oops to max_reason for now.
> > +static inline int psz_kmsg_erase(struct psz_context *cxt,
> > + struct pstore_zone *zone, struct pstore_record *record)
> > +{
> > + struct psz_buffer *buffer = zone->buffer;
> > + struct psz_kmsg_header *hdr =
> > + (struct psz_kmsg_header *)buffer->data;
> > +
> > + if (unlikely(!psz_ok(zone)))
> > + return 0;
> > + /* this zone is already updated, no need to erase */
> > + if (record->count != hdr->counter)
> > + return 0;
>
> These codes is to fix bug that user remove files on pstore filesystem
> but kmsg zone is already updated and pstore/zone should not erase
> zone. It work for oops and panic because the count number is increasing.
> However, it's useless for other reason of kmsg. We can fix it after this
> series.
Okay, sounds good.
--
Kees Cook
