Messages in this thread | | | Date | Wed, 2 Feb 2011 11:33:42 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] ptrace: use safer wake up on ptrace_detach() |
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On Wed, 2 Feb 2011 11:34:02 +0100 Tejun Heo <tj@kernel.org> wrote:
> Hello, > > On Tue, Feb 01, 2011 at 09:38:28PM -0800, Andrew Morton wrote: > > On Tue, 1 Feb 2011 21:33:31 -0800 (PST) Roland McGrath <roland@redhat.com> wrote: > > > > > > Am unable to work out why you tagged it for backporting. It fixes some > > > > observed bug? Perhaps a regression? > > > > > > No observed bug, only theoretical ones (AFAIK, never even a ginned-up > > > synthetic test case has been demonstrated). Certainly not a regression, > > > since it has been this (wrong) way since the dawn of time. I don't think > > > this first change is dangerous for -stable, but I have seen no positive > > > rationale for pushing it there. > > > > > > > OK, thanks. I shall destabilize my copy of this patch. > > It can be used as an attack vector. I don't think it will take too > much effort to come up with an attack which triggers oops somewhere. > Most sleeps are wrapped in condition test loops and should be safe but > we have quite a number of places where sleep and wakeup conditions are > expected to be interlocked. Although the window of opportunity is > tiny, ptrace can be used by non-privileged users and with some loading > the window can definitely be extended and exploited. > > The chance of this problem being visible under normal usage is > extremely low so no wonder there is no related bug report but that is > very different from being safe against targeted attacks. > > As the likelihood of causing user noticeable breakage is very low, I > think we better push it through -stable. >
We're learning some lessons about changelogging here :(
I added this:
: This bug can possibly be used as an attack vector. I don't think : it will take too much effort to come up with an attack which triggers : oops somewhere. Most sleeps are wrapped in condition test loops and : should be safe but we have quite a number of places where sleep and : wakeup conditions are expected to be interlocked. Although the : window of opportunity is tiny, ptrace can be used by non-privileged : users and with some loading the window can definitely be extended and : exploited.
to the changelog so the -stable maintainers can understand why we're sending this patch at them.
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