From f60007c9e91402d936e300913eed62fa7fc2e54b Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 24 Feb 2020 15:01:39 +0100 Subject: [PATCH] bpf: Remove recursion prevention from rcu free callback [ Upstream commit 8a37963c7ac9ecb7f86f8ebda020e3f8d6d7b8a0 ] If an element is freed via RCU then recursion into BPF instrumentation functions is not a concern. The element is already detached from the map and the RCU callback does not hold any locks on which a kprobe, perf event or tracepoint attached BPF program could deadlock. Signed-off-by: Thomas Gleixner Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20200224145643.259118710@linutronix.de Signed-off-by: Sasha Levin --- kernel/bpf/hashtab.c | 8 -------- 1 file changed, 8 deletions(-) diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index 039d64b1bfb7..728ffec52cf3 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -664,15 +664,7 @@ static void htab_elem_free_rcu(struct rcu_head *head) struct htab_elem *l = container_of(head, struct htab_elem, rcu); struct bpf_htab *htab = l->htab; - /* must increment bpf_prog_active to avoid kprobe+bpf triggering while - * we're calling kfree, otherwise deadlock is possible if kprobes - * are placed somewhere inside of slub - */ - preempt_disable(); - __this_cpu_inc(bpf_prog_active); htab_elem_free(htab, l); - __this_cpu_dec(bpf_prog_active); - preempt_enable(); } static void htab_put_fd_value(struct bpf_htab *htab, struct htab_elem *l)