From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ian Jackson <Ian.Jackson@eu.citrix.com>
Subject: Re: [PATCH 15/22] libelf: use only unsigned integers
Date: Tue, 11 Jun 2013 14:16:01 +0100
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To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>, "mattjd@gmail.com" <mattjd@gmail.com>, "security@xen.org" <security@xen.org>
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Andrew Cooper writes ("Re: [PATCH 15/22] libelf: use only unsigned integers"):
> On 07/06/13 19:27, Ian Jackson wrote:
> >  ELF_PTRVAL_CONST_VOID elf_note_desc(struct elf_binary *elf, ELF_HANDLE_DECL(elf_note) note)
> >  {
> > -    int namesz = (elf_uval(elf, note, namesz) + 3) & ~3;
> > +    unsigned namesz = (elf_uval(elf, note, namesz) + 3) & ~3;
> 
> Here and elsewhere in this patch:
> 
> namesz is a guest-provided parameter.  If it is sufficiently high,
> namesz + 3 will overflow and end up being 0 after the rounding.
> 
> The result of this function would then falsely be elf_note_name() instead.

Yes, but I don't understand why it's a security problem.  If a
guest-provided kernel is corrupted then the guest should get to keep
all the resulting pieces.

Ian.