[PATCH v4] readelf: Save and dump the original section header values

[H.J. Lu]

On Thu, Jul 9, 2026 at 2:55 PM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 09.07.2026 08:32, H.J. Lu wrote:
> > On Thu, Jul 9, 2026 at 2:06 PM Jan Beulich <jbeulich@suse.com> wrote:
> >>
> >> On 04.07.2026 13:06, H.J. Lu wrote:
> >>> On Sat, Jul 4, 2026 at 11:01 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> >>>> On Sat, Jul 4, 2026 at 8:39 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> >>>>> On Sat, Jul 4, 2026 at 7:49 AM Alan Modra <amodra@gmail.com> wrote:
> >>>>>>
> >>>>>> On Fri, Jul 03, 2026 at 10:30:14PM +0800, H.J. Lu wrote:
> >>>>>>> validate_section_info clears the garbage values in the section header
> >>>>>>> to avoid crash later.  Save and dump the original section header values
> >>>>>>> to make the garbage values in the section header visible when dumping
> >>>>>>> section headers.
> >>>>>>
> >>>>>> I think this would be better done the other way around.  ie. have a
> >>>>>> Elf_Internal_Shdr **sane_section_headers that is initialised to point
> >>>>>> at entries in section_headers, with sane_section_headers[i] allocated
> >>>>>> as necessary when needing to correct a bogus header.
> >>>>>>
> >>>>>
> >>>>> I have thought about something similar and decided against it
> >>>>> since filedata->section_headers is used in many places.   However,
> >>>>> I can change filedata->orig_section_headers to on demand.
> >>
> >> I find this a plausible argument, so ...
> >>
> >>>> Changes in v2:
> >>>>
> >>>> 1.  filedata->orig_section_headers is changed to on demand.
> >>>
> >>> Changes in v3:
> >>>
> >>> 1.  Clear filedata->orig_section_headers first.
> >>
> >> ... the patch is okay unless you get an objection from Alan within another
> >
> > Will do.
> >
> >> day or two. Just one thing though: calloc() + memset(, 0,) is redundant.
> >> Please drop those memset()s.
> >
> > It is cmalloc, not calloc:
> >
> >   filedata->orig_section_headers = (Elf_Internal_Shdr **)
> >     cmalloc (num, sizeof (Elf_Internal_Shdr *));
> >
> > cmalloc doesn't clear memory.  memset is needed.
>
> Seeing that cmalloc() uses xmalloc() (not malloc()), why don't you then
> simply use xcmalloc2()?

Did you mean xcalloc2?

> Further, again seeing that cmalloc() uses xmalloc() - the NULL checks
> that you add are then solely to cover the multiplication overflow case.
> That doesn't match the use of malloc() elsewhere in the patch.
>
> Taken together, why is it that calloc() isn't used here in the first
> place (to match the use of malloc())? There's no truncation risk on the
> first argument passed, and surely a sane implementation of calloc() has
> to check for overflow of the multiplication when determining overall

I guess we don't know what calloc will be used.

> size.
>
> Jan

Here is the v4 patch to use xcalloc2.

-- 
H.J.
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