Re: [Xen-devel] [PATCH v7 00/22] XSA55 libelf fixes for unstable

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Ian Jackson writes ("Re: [PATCH v7 00/22] XSA55 libelf fixes for unstable"):
> I have had a review from Oracle by private email.  Prompted by that
> review I did a search and now I'm suspicious of a range test in
> xc_dom_alloc_segment.

The status of this is as follows:

I have no review as yet of the post-v7 patch:
 23/?? libxc: Better range check in xc_dom_alloc_segment
just posted by me in the v7 00/22 subthread.

I only have one formal review (Andrew Cooper's) on:
 03/22 159 libxc: Fix range checking in xc_dom_pfn_to_ptr etc.
 15/22 773 libelf: use only unsigned integers
 16/22 413 libelf: check loops for running away
 18/22  72 libxc: Add range checking to xc_dom_binloader
 19/22 322 libxc: check failure of xc_dom_*_to_ptr, xc_map_foreign_range
 20/22 307 libxc: check return values from malloc
 21/22  47 libxc: range checks in xc_dom_p2m_host and _guest
(numbers are length of the patch file in lines).

On these patches I have Andrew Cooper's review on the latest version
but other review(s) on earlier versions which I decided not to
consider applied to the current version:
 11/22 libelf: check all pointer accesses    [v2 acked by Ian Campbell]

Of these I think the most troublesome areas are:
 15: Risk of regressions and other unintended functional changes.
 16: Risk of regressions or of failure to catch all problematic loops.
 18: Risk of failure to catch all problems in this fiddly code.

I'm still waiting for a comment from Tim Deegan or some other
hypervisor memory arrangemente expert on patch 21, on what
xc_dom_p2m_host and xc_dom_p2m_guest should do with out-of-range pfns
in shadow mode.  Should they turn them into INVALID_MFN rather than
simply returning them ?  (And is the definition of "invalid" the same
as for non-shadow, ie using rambase_pfn and total_pages.()

Thanks,
Ian.

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