Re: [syzbot] [bpf?] BUG: using smp_processor_id() in preemptible code in bpf_mem_cache_free_rcu

[Edward Adam Davis]

#syz test

diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c
index bd45dda9dc35..1d7ddfc1c9d1 100644
--- a/kernel/bpf/memalloc.c
+++ b/kernel/bpf/memalloc.c
@@ -957,7 +957,9 @@ void notrace bpf_mem_cache_free_rcu(struct bpf_mem_alloc *ma, void *ptr)
 	if (!ptr)
 		return;
 
+	get_cpu();
 	unit_free_rcu(this_cpu_ptr(ma->cache), ptr);
+	put_cpu();
 }
 
 /* Directly does a kfree() without putting 'ptr' back to the free_llist