On Wed, Oct 30, 2019 at 05:34:28PM +0800, Yunsheng Lin wrote: > When passing the return value of dev_to_node() to cpumask_of_node() > without checking if the device's node id is NUMA_NO_NODE, there is > global-out-of-bounds detected by KASAN. > > From the discussion [1], NUMA_NO_NODE really means no node affinity, > which also means all cpus should be usable. So the cpumask_of_node() > should always return all cpus online when user passes the node id as > NUMA_NO_NODE, just like similar semantic that page allocator handles > NUMA_NO_NODE. > > But we cannot really copy the page allocator logic. Simply because the > page allocator doesn't enforce the near node affinity. It just picks it > up as a preferred node but then it is free to fallback to any other numa > node. This is not the case here and node_to_cpumask_map will only restrict > to the particular node's cpus which would have really non deterministic > behavior depending on where the code is executed. So in fact we really > want to return cpu_online_mask for NUMA_NO_NODE. > > Also there is a debugging version of node_to_cpumask_map() for x86 and > arm64, which is only used when CONFIG_DEBUG_PER_CPU_MAPS is defined, this > patch changes it to handle NUMA_NO_NODE as normal node_to_cpumask_map(). > > [1] https://lkml.org/lkml/2019/9/11/66 > Signed-off-by: Yunsheng Lin <linyunsheng@xxxxxxxxxx> > Suggested-by: Michal Hocko <mhocko@xxxxxxxxxx> > Acked-by: Michal Hocko <mhocko@xxxxxxxx> > Acked-by: Paul Burton <paul.burton@xxxxxxxx> # MIPS bits Still: Nacked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
