From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ed1-f45.google.com (mail-ed1-f45.google.com [209.85.208.45]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 46D9259B71 for ; Tue, 22 Oct 2024 21:08:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.208.45 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729631321; cv=none; b=HvpKT0j2N328hmj/cw4aSomVUaUzRuBpcK/xvcqRic+DHPFKIg3R2ppEV/Pj2JqIJgqWnI2owYui8wo9o4Ullds77mrkgedn3YgFaoddknncaZX0OiP52Gw4mTZVLGOQ2RAShjMxeNaMzXZAIVEGKTaXcp/oEWUBEAsaBRNEXQo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729631321; c=relaxed/simple; bh=Xjkh40l5vufdwsVJi34MeQcxCKaA1g1UjKdcEwBvBQs=; h=From:Date:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Buorz+NoyAKWqIRd5hBUUbZY7vW7WT6F8S2JgbwWIRtk+VTzbRiNHl+7W4lzUKQhlX5oFMC0c9Jfog9+1+d+hEgymAkQUYGUiejPEu/1d2rnIa2jtXb22LVQGtjRYQp/tjnNh/fJ3a7ZAS2AGDvf7nEbJEc2bNgQCc+tirtgmQY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=Ol3FfQ6p; arc=none smtp.client-ip=209.85.208.45 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Ol3FfQ6p" Received: by mail-ed1-f45.google.com with SMTP id 4fb4d7f45d1cf-5c95a962c2bso7358250a12.2 for ; Tue, 22 Oct 2024 14:08:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1729631318; x=1730236118; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:from:to:cc:subject:date:message-id:reply-to; bh=OlGVD1afRO0J0hySzv5lIBijcdOAPnGH7GUqjHaMbBA=; b=Ol3FfQ6pgPBxDBTwXiZZYEQRZfqQ3jc9xiOZY6e5l+7A9qLi21y6jgBkfix6iD1vNn 18fBIZi5++/JUbcSJ+r0xsSH9TRLDxVpmoEtkLFZMZVGuvvlC5STbDff60U3g4BMgGW5 ksbKwRa+BgsIIOreK0DOHKgBn07Kf/DbF652+MGZzKIwRWnoTk1GxG+k1kGt2KDuAZge z6mFKLgNkq0xVaHenI6vFBuGbK1/RO7J8M+VJLt0gqNyDP5l4chYvCwtnDIQA6nvT4/Q SMN2k8bboKzCE9G+3sN3S474UhbGxjWt83g+QBXIcC8l9rOSY23Yyhei6TmOrZXuZMMw Cwsg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1729631318; x=1730236118; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=OlGVD1afRO0J0hySzv5lIBijcdOAPnGH7GUqjHaMbBA=; b=OtUazyngg7m6Dnq6wueoQB0lfD405nFfTpZp+cXG6fUm6BAAGvhkczzcEmgeMpB6EG gROUXsN/Y0LwszvGd0z25mWqbG3PWuRA1mlGP37X+vTW1+w5MUQFRrYrcDvrZZmPtSvB FX3cZWuXRKmNNBLeGX5KfqARIREUAjFle9NsCVoM74IYTPL30ecDY8teFHFFhsj+M4il e7I8RmRisv9PeDQj1KBt8qmNBCHr+mNTW0LGwnZHdDUPqwLXDBRNHpP/zPlSbx7bcba8 OcJSES6ee2Wse0qnFSP+XU+k/qMgJR9uNWqF9nJ8oHB8Y5PiYwZDTJNrhkC/AalaJ3Vf ukqA== X-Forwarded-Encrypted: i=1; AJvYcCXiVJn8hiFxFQ7i0OjiooLdRHoBzWcVaZnE05IIX9wsuuQsVlK3ojg0WYrexatd26Y5ZUuxoNhap9tU/po=@vger.kernel.org X-Gm-Message-State: AOJu0YzAoDsCeRZP6Z4I8+SEyCucoiszVfYty2qo9vkXF4w/yxSdGsaO aJ1ZY12oO5ZPGLj9LavN2W8zuu4HXR0oZTmEpcyFeHHjeLXFEtrp X-Google-Smtp-Source: AGHT+IFFVdf8pqWTuEQkBRUxBKqit4E0lHS9zIxLQSP7StFEjoXKZHYFRqZpd6WtkkmoMmjw7nwC2Q== X-Received: by 2002:a17:907:3e02:b0:a9a:222f:45d1 with SMTP id a640c23a62f3a-a9abf86a5b5mr27086766b.20.1729631318215; Tue, 22 Oct 2024 14:08:38 -0700 (PDT) Received: from krava (85-193-35-199.rib.o2.cz. [85.193.35.199]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a9a912f7db1sm385074466b.89.2024.10.22.14.08.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Oct 2024 14:08:37 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Tue, 22 Oct 2024 23:08:36 +0200 To: Sean Young Cc: Jiri Olsa , Peter Zijlstra , andrii@kernel.org, yhs@fb.com, linux-kernel@vger.kernel.org, daniel@iogearbox.net Subject: Re: perf_event_detach_bpf_prog() broken? Message-ID: References: <20241022111638.GC16066@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Oct 22, 2024 at 03:12:38PM +0100, Sean Young wrote: > On Tue, Oct 22, 2024 at 04:03:40PM +0200, Jiri Olsa wrote: > > On Tue, Oct 22, 2024 at 01:16:38PM +0200, Peter Zijlstra wrote: > > > Hi guys, > > > > > > Per commit 170a7e3ea070 ("bpf: bpf_prog_array_copy() should return > > > -ENOENT if exclude_prog not found") perf_event_detach_bpf_prog() can now > > > return without doing bpf_prog_put() and leaving event->prog set. > > > > > > This is very 'unexpected' behaviour. > > > > > > I'm not sure what's sane from the BPF side of things here, but leaving > > > event->prog set is really rather unexpected. > > > > > > Help? > > > > IIUC the ENOENT should never happen in perf event context, so not > > sure why we have that check.. also does not seem to be used from > > lirc code, Sean? > > You can deattach a lirc program using the bpf syscall with command > BPF_PROG_DETACH, and if you pass an incorrect (as in, not attached) program, > then this commit ensures you get ENOENT rather than success. I see.. so that's for lirc programs, but we can't detach perf event's program like that the program is stored in event and is detached and released only when the event is freed, so even for ENOENT error (which can't happen) we still need to release the event's program I think we can just remove the check like below jirka --- diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index e7370a321126..e4e22499956d 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2240,8 +2240,6 @@ void perf_event_detach_bpf_prog(struct perf_event *event) old_array = bpf_event_rcu_dereference(event->tp_event->prog_array); ret = bpf_prog_array_copy(old_array, event->prog, NULL, 0, &new_array); - if (ret == -ENOENT) - goto unlock; if (ret < 0) { bpf_prog_array_delete_safe(old_array, event->prog); } else {