[PATCH]: Bug in ppc32 ld.so

Benjamin Herrenschmidt benh at kernel.crashing.org
Sat May 11 07:13:53 EST 2002

>Hi Ben,
>Its seems Geoff Keating and Anton are debating whether this patch should
>not be included in glibc and instead the new kernel behavior be reverted
>to icache synchronizing zero'd pages handed out by the kernel.
>It seems Geoff thinks there may be a security risk in allowing the stale
>code in the instruction cache code to be run and some benefit result by a
>malicious process (not just library loading obviously).
>So people might want to wait on this patch until things get flushed out
>(puin intended!).
>Either way, I would rather have a ld.so doing the complete icbi cache flush
>anyway since it makes me feel safer inside!  I have been bitten by too
>many cache flush related errors and I favor great overkill!

I fully agree with you ! Whatever we decide to do with the kernel
cache flush code, let's do the proper icbi in ld.so.

>The discussion is on the libc-alpha mailing list (just follow the link I
>sent and go to followups at the bottom).
>Do you know where in the kernel this change was made by Paul  (head.S with
>the zero page code? idle.c - with its zero page code during idle, or
>misc.S where the cache flush routines are now or ...).  I am trying to
>figure out when (what specific 2.4 kernel revision)  this came into.

clear_user_page, somewhere in arch/ppc/mm

>Thought you might like to know.
>On May 10, 2002 02:06, Benjamin Herrenschmidt wrote:
>> >Hi Anton,
>> >
>> >I saw:
>> >
>> >http://sources.redhat.com/ml/libc-alpha/2002-05/msg00052.html
>> >
>> >Thanks for posting that patch.  Have you by any chance alerted or sent
>> >similar mail to YDL dev lists, Debian dev lists, SuSE dev lists, and
>> >dev at linuxppc.
>> >
>> >This would be a nasty bug to track down and those distributions may
>> > want to know about this and get an udpated glibc-2.2.5 packages posted
>> > on their sites for those brave users who are using later 2.4 kernels?
>> >
>> >BTW, any idea when this change by Paul was introduced into the 2.4
>> > kernel series (specifically which 2.4.XX kernel?).
>> I submited a debian bug report with Anton message, Olaf (suse) is on
>> the linuxppc64 list and had the patch, YDL folks have or will have it
>> rsn (thanks to IRC magic ;)
>> Ben.

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