bpf, perf: delay release of BPF prog after grace period
authorDaniel Borkmann <daniel@iogearbox.net>
Mon, 27 Jun 2016 19:38:11 +0000 (21:38 +0200)
committerDavid S. Miller <davem@davemloft.net>
Wed, 29 Jun 2016 09:42:55 +0000 (05:42 -0400)
commitceb56070359b7329b5678b5d95a376fcb24767be
tree0f6deeff3c087009986f95158f27e1d2bd9ae549
parent565ce8f32ac4a233b474f401e1d3e7e1de0a31fd
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 <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Cc: Jann Horn <jann@thejh.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
include/linux/bpf.h
kernel/events/core.c