Fixing the glibc adobe flash incompatibility

nodata lsof at nodata.co.uk
Wed Nov 17 09:17:52 UTC 2010


On 17/11/10 08:57, Hans de Goede wrote:
> Hi all,
>
> For those who do not know it yet, recent Fedora glibc updates include
> an optimized memcpy (which gets used on some processors) which breaks the
> 64 bit adobe flash plugin.
>
> The problem has been analyzed and is known, as well as a fix for it, see:
> https://bugzilla.redhat.com/show_bug.cgi?id=638477
>
> The problem still exists however. The glibc developers say that this is
> not a glibc bug, but a flash plugin bug. And technically they are 100%
> correct, and the adobe flash plugin is a buggy .... (no surprise there).
> To be specific the flash plugin is doing overlapping memcpy-s which is
> clearly not how memcpy is supposed to be used. But the way the flash
> plugin does overlapping memcpy's happens to work fine as long as one as
> the c library does the memcpy-s in forward direction. And the new memcpy
> implementation does the memcpy in backward direction.
>
> The glibc developers being technically 100% correct is not helping our
> end users in this case though. So we (The Fedora project) need to come up
> with a solution to help our end users, many of whom want to use the adobe
> flash plugin.
>
> This solution could be reverting the problem causing glibc change, or
> maybe changing it to do forward memcpy's while still using the new SSE
> instructions, or something more specific to the flash plugin, as long
> as it will automatically fix things with a yum upgrade without requiring
> any further user intervention.
>
> I would also like to point out that if this were to happen in Ubuntu
> which we sometimes look at jealously for getting more attention / users
> then us, the glibc change would likely be reverted immediately, as that
> is the right thing to do from an end user pov.
>
> I've filed a ticket for FESCo to look into this, as I believe this
> makes us look really bad, and the glibc maintainers do not seem to be
> willing to fix it without some sort of intervention:
> https://fedorahosted.org/fesco/ticket/501
>
> Regards,
>
> Hans

Is someone talking to Adobe about this?


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