Re: [PATCH] uprobes: Fix handle_swbp() vs. unregister() + register() race once more

[Oleg Nesterov <oleg@redhat.com>]

On 11/22, Oleg Nesterov wrote:
> On 11/22, Andrea Parri wrote:
> >
> > Commit 142b18ddc8143 ("uprobes: Fix handle_swbp() vs unregister() +
> > register() race") added the UPROBE_COPY_INSN flag, and corresponding
> > smp_wmb() and smp_rmb() memory barriers, to ensure that handle_swbp()
> > uses fully-initialized uprobes only.
> > 
> > However, the smp_rmb() is mis-placed: this barrier should be placed
> > after handle_swbp() has tested for the flag, thus guaranteeing that
> > (program-order) subsequent loads from the uprobe can see the initial
> > stores performed by prepare_uprobe().
> > 
> > Move the smp_rmb() accordingly.  Also amend the comments associated
> > to the two memory barriers to indicate their actual locations.
> > 
> > Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
> > Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> > Cc: Jiri Olsa <jolsa@redhat.com>
> > Cc: Namhyung Kim <namhyung@kernel.org>
> > Cc: Oleg Nesterov <oleg@redhat.com>
> > Cc: stable@kernel.org
> > Fixes: 142b18ddc8143 ("uprobes: Fix handle_swbp() vs unregister() + register() race")
> 
> Thanks,
> 
> Acked-by: Oleg Nesterov <oleg@redhat.com>

Yes, but I am not sure this is the -stable material...

Oleg.