On Wed 30-10-19 11:14:49, Peter Zijlstra wrote: > 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> Do you have any other proposal that doesn't make any wild guesses about which node to use instead of the undefined one? -- Michal Hocko SUSE Labs
