bugGNU GRUB - Bugs: bug #50237, Wrong descsz in Xen ELF note 9...


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bug #50237: Wrong descsz in Xen ELF note 9 (PAE_MODEL)

Submitted by:  Sergio Gelato <gelato>
Submitted on:  Mon 06 Feb 2017 08:56:23 AM UTC  
Category:  None Severity:  Major
Priority:  5 - Normal Item Group:  None
Status:  None Privacy:  Public
Assigned to:  None Originator Name: 
Open/Closed:  Open Release: 
Release:  other Reproducibility:  Every Time
Planned Release:  2.03+

Thu 09 Feb 2017 06:33:47 PM UTC, comment #1:

Yes, this looks wrong, but unless you can provide test case where it breaks, it is post 2.02 cleanup. Looking at note description, it will actually affect only older Xen versions. Otherwise it should simply get "yes" string.

grub-mkimage was created long before xen headers were imported into grub tree.

Feel free to submit cleanup patch to grub-devel. Please split it in to commits (one for "yes,bimodal" and one for using symbolic names.

Andrei Borzenkov <arvidjaar>
Project Member
Mon 06 Feb 2017 08:56:23 AM UTC, original submission:

In util/grub-mkimagexx.c, the code that sets up ELF notes for IMAGE_XEN on EM_386 is not self-consistent: it has

note_ptr->n_descsz = grub_host_to_target32 (sizeof ("yes,bimodal"));

followed by

memcpy (ptr, "yes", sizeof ("yes"));
ptr += ALIGN_UP (sizeof ("yes"), 4);

As a result, the note is shorter than its header implies.

The defined value of XEN_NOTE_SIZE in util/grub-mkimage32.c is consistent with the actual length of the note, so the likelier fix is to change note_ptr->n_descsz to be grub_host_to_target32 (sizeof ("yes")) .

I noticed this by source code inspection while researching bug #46014. Unfortunately, fixing this issue doesn't seem to solve that bug.

(Aside: maybe util/grub-mkimagexx.c should make use of the named symbols defined in include/xen/elfnote.h ?)

Sergio Gelato <gelato>


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    Follows 1 latest change.

    Date Changed by Updated Field Previous Value => Replaced by
    2017-02-09 arvidjaar Planned ReleaseNone => 2.03+

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