On 05/31/23 at 10:19am, Leizhen (ThunderTown) wrote:
>
>
> On 2023/5/31 8:17, Baoquan He wrote:
> > On 05/27/23 at 08:34pm, Zhen Lei wrote:
> >> The check '(crashk_res.parent != NULL)' is added by
> >> commit e05bd3367bd3 ("kexec: fix Oops in crash_shrink_memory()"), but it's
> >> stale now. Because if 'crashk_res' is not reserved, it will be zero in
> >> size and will be intercepted by the above 'if (new_size >= old_size)'.
> >>
> >> Ago:
> >> if (new_size >= end - start + 1)
> >>
> >> Now:
> >> old_size = (end == 0) ? 0 : end - start + 1;
> >> if (new_size >= old_size)
> >
> > Hmm, I would strongly suggest we keep that check. Even though the
> > current code like above can do the acutal checking, but its actual usage
> > is not obvious for checking of crashk_res existence. In the future,
> > someone may change above calculation and don't notice the hidden
> > functionality at all behind the calculation. The cost of the check is
> > almost zero, right?
>
> The cost of the check is negligible. The only downside is that it's hard to
> understand why it's added, and I only found out why by looking at the history
> log. In my opinion, the above 'Now:' is the right fix.
It checks if the resource exists before releasing, just a normal
checking?
>
> >
> >>
> >> Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
> >> ---
> >> kernel/kexec_core.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> >> index 22acee18195a591..d1ab139dd49035e 100644
> >> --- a/kernel/kexec_core.c
> >> +++ b/kernel/kexec_core.c
> >> @@ -1137,7 +1137,7 @@ int crash_shrink_memory(unsigned long new_size)
> >> end = start + new_size;
> >> crash_free_reserved_phys_range(end, crashk_res.end);
> >>
> >> - if ((start == end) && (crashk_res.parent != NULL))
> >> + if (start == end)
> >> release_resource(&crashk_res);
> >>
> >> ram_res->start = end;
> >> --
> >> 2.25.1
> >>
> >
> > .
> >
>
> --
> Regards,
> Zhen Lei
>
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