On 02/26/16 at 04:56pm, Andrew Morton wrote:
> On Thu, 25 Feb 2016 22:02:40 +0800 Minfei Huang <mhuang at redhat.com> wrote:
>
> > From: Minfei Huang <mnfhuang at gmail.com>
> >
> > For some arch, kexec shall map the reserved pages, then use them, when
> > we try to start the kdump service.
> >
> > kexec may return directly, without unmaping the reserved pages, if it
> > fails during starting service. To fix it, we make a pair of map/unmap
> > reserved pages both in generic path and error path.
>
> This patch both refactors the code AND fixes the bug. It is a
> decent-looking refactoring, but mixing the two together makes it *much*
> harder to review the bugfix. These two steps should be separated
> please, with the bugfix patch coming first.
I will bisect this patch to make it more simple to be reviewed.
>
> > --- a/kernel/kexec.c
> > +++ b/kernel/kexec.c
> > @@ -103,6 +103,68 @@ out_free_image:
> > return ret;
> > }
> >
> > +static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
> > + struct kexec_segment __user *segments, unsigned long flags)
> > +{
> > + struct kimage **dest_image, *image;
> > + unsigned long i;
> > + int ret;
> > +
> > + if (flags & KEXEC_ON_CRASH)
> > + dest_image = &kexec_crash_image;
> > + else
> > + dest_image = &kexec_image;
> > +
> > + if (nr_segments == 0) {
> > + /* Uninstall image */
> > + kimage_free(xchg(dest_image, NULL));
> > + return 0;
> > + }
> > + if (flags & KEXEC_ON_CRASH) {
> > + /*
> > + * Loading another kernel to switch to if this one
> > + * crashes. Free any current crash dump kernel before
> > + * we corrupt it.
> > + */
> > + kimage_free(xchg(&kexec_crash_image, NULL));
> > + }
> > +
> > + ret = kimage_alloc_init(&image, entry, nr_segments, segments, flags);
> > + if (ret)
> > + return ret;
>
> This is a bug, isn't it? Missed kimage_free().
The variable image is NULL, if kimage_alloc_init returns with error. And
kimage_alloc_init will do the cleanup before returning. So it's fine
without calling kimage_free.
Thanks
Minfei
