From ceb56070359b7329b5678b5d95a376fcb24767be Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Mon, 27 Jun 2016 21:38:11 +0200 Subject: bpf, perf: delay release of BPF prog after grace period Commit dead9f29ddcc ("perf: Fix race in BPF program unregister") moved destruction of BPF program from free_event_rcu() callback to __free_event(), which is problematic if used with tail calls: if prog A is attached as trace event directly, but at the same time present in a tail call map used by another trace event program elsewhere, then we need to delay destruction via RCU grace period since it can still be in use by the program doing the tail call (the prog first needs to be dropped from the tail call map, then trace event with prog A attached destroyed, so we get immediate destruction). Fixes: dead9f29ddcc ("perf: Fix race in BPF program unregister") Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Cc: Jann Horn Signed-off-by: David S. Miller --- include/linux/bpf.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include/linux/bpf.h') diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 8269caf..0de4de6 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -264,6 +264,10 @@ static inline struct bpf_prog *bpf_prog_get(u32 ufd) static inline void bpf_prog_put(struct bpf_prog *prog) { } + +static inline void bpf_prog_put_rcu(struct bpf_prog *prog) +{ +} #endif /* CONFIG_BPF_SYSCALL */ /* verifier prototypes for helper functions called from eBPF programs */ -- cgit v1.1