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Date: Sun, 16 Feb 2020 20:29:57 +0100 From: Jiri Olsa <jolsa@...nel.org> To: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net> Cc: netdev@...r.kernel.org, bpf@...r.kernel.org, Andrii Nakryiko <andriin@...com>, Yonghong Song <yhs@...com>, Song Liu <songliubraving@...com>, Martin KaFai Lau <kafai@...com>, Jakub Kicinski <kuba@...nel.org>, David Miller <davem@...hat.com>, Björn Töpel <bjorn.topel@...el.com>, John Fastabend <john.fastabend@...il.com>, Jesper Dangaard Brouer <hawk@...nel.org>, Arnaldo Carvalho de Melo <acme@...hat.com> Subject: [PATCH 10/18] bpf: Re-initialize lnode in bpf_ksym_del When bpf_prog is removed from kallsyms it's on the way out to be removed, so we don't care about lnode state. However the bpf_ksym_del will be used also by bpf_trampoline and bpf_dispatcher objects, which stay allocated even when they are not in kallsyms list, hence the lnode re-init. The list_del_rcu commentary states that we need to call synchronize_rcu, before we can change/re-init the list_head pointers. Signed-off-by: Jiri Olsa <jolsa@...nel.org> --- kernel/bpf/core.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 739bef60d868..a0feba447e5d 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -676,6 +676,13 @@ void bpf_ksym_del(struct bpf_ksym *ksym) spin_lock_bh(&bpf_lock); __bpf_ksym_del(ksym); spin_unlock_bh(&bpf_lock); + + /* + * As explained in list_del_rcu, We must call synchronize_rcu + * before changing list_head pointers. + */ + synchronize_rcu(); + INIT_LIST_HEAD_RCU(&ksym->lnode); } static bool bpf_prog_kallsyms_candidate(const struct bpf_prog *fp) -- 2.24.1
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