Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix missing migration protection in __rhtab_map_lookup_and_delete_batch()

bpf_mem_cache_free_rcu() uses this_cpu_ptr() which requires migration to be disabled. All callers of rhtab_delete_elem() disable migration except __rhtab_map_lookup_and_delete_batch(), which calls it under rcu_read_lock() only.

On CONFIG_PREEMPT_RCU, rcu_read_lock() does not disable preemption or migration, so the task can migrate between CPUs during the delete loop, causing this_cpu_ptr() to trigger:

BUG: using smp_processor_id() in preemptible [00000000] code

Fix by wrapping the delete loop in migrate_disable()/migrate_enable() in __rhtab_map_lookup_and_delete_batch(), matching the migration protection that the other callers already provide.