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Re: [PATCH 1/2] unstrip: Don't try to use unstripped .symtab with stripped .strtab
- From: Mark Wielaard <mjw at redhat dot com>
- To: elfutils-devel at lists dot fedorahosted dot org
- Date: Mon, 24 Oct 2016 13:09:34 +0200
- Subject: Re: [PATCH 1/2] unstrip: Don't try to use unstripped .symtab with stripped .strtab
On Sun, 2016-10-23 at 10:25 -0700, Kevin Cernekee wrote:
> Prematurely matching up the stripped and unstripped .strtab sections
> in the "Match each debuginfo" loop can lead to a case where sec->outscn
> gets populated for the stripped .strtab, which we normally want to
> ignore. This causes the .strtab override in the "Make sure each main
> file section" loop to be skipped, so the code winds up using indices
> from the unstripped .symtab to look up strings in the stripped .strtab.
> This returns incorrect strings for a little while, and then fails
> catastrophically when it tries to read past the end of the (smaller)
> stripped file's .strtab section:
> eu-unstrip: invalid string offset in symbol 
> Fix this by adding logic to the "Match each debuginfo" loop to
> treat the unstripped .strtab, .shstrtab, and .symtab sections
> essentially the same way.
Looks good. Thanks for the analysis and the fix.
Applied to git master.
> The new logic will break if the .strtab section shows up earlier than
> the .symtab section. We will assume this never happens in practice.
grin. This screams for someone to show up with such a file tomorrow :)
But in practice this indeed doesn't happen because all tools create the
sections in order. If someone does create such a file with the sections
reversed we'll have to add another pass over the section headers.
> Signed-off-by: Kevin Cernekee <firstname.lastname@example.org>