On Wed, Jan 03, 2018 at 10:38:27PM +0000, Mark Rutland wrote: > Under speculation, CPUs may mis-predict branches in bounds checks. Thus, > memory accesses under a bounds check may be speculated even if the > bounds check fails, providing a primitive for building a side channel. > > The EBPF map code has a number of such bounds-checks accesses in > map_lookup_elem implementations. This patch modifies these to use the > nospec helpers to inhibit such side channels. > > The JITted lookup_elem implementations remain potentially vulnerable, > and are disabled (with JITted code falling back to the C > implementations). Since this is now public, let me re-iterate that I don't particularly like this approach. If you have to kill the JIT, could we please keep that in the arch JIT implementation?
