From patchwork Tue Sep 29 10:57:44 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 290950 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3AA28C4727C for ; Tue, 29 Sep 2020 12:08:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E38A6206CD for ; Tue, 29 Sep 2020 12:08:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601381289; bh=z7GkIRBfIpqHZ8dIEWx/p44xdirXNH0oyPkAC+8qQJg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=A6+HMlZFoukC5fHSC0z4cbgpYmqdvBkE6A4EBT2uABZbjH0NI3MSQgjp6LNl5AP7N 607f3J/vzRipyoea2B24kuh5tk7PRcCOIqkzwPnKvAq9KU/AYBmS8L6hegoEEH/hyA aXDqeTW+0CMAbEfPWZw4IVQ1L5pvC2XfUfdU8Eg8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730769AbgI2MII (ORCPT ); Tue, 29 Sep 2020 08:08:08 -0400 Received: from mail.kernel.org ([198.145.29.99]:58098 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730237AbgI2Lhg (ORCPT ); Tue, 29 Sep 2020 07:37:36 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E23F023A9C; Tue, 29 Sep 2020 11:36:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601379370; bh=z7GkIRBfIpqHZ8dIEWx/p44xdirXNH0oyPkAC+8qQJg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Xrs16mYGG5Md+t5vMzxlPUyDsqCQlqPHJH6U88517d9TwExFDy1i+Y9mca0CvD9n5 +CKVUT2IqMX3G6iHuzaAzhRYxYuQLq7o6vzymnLu7BnOKdqputGFFV2VYJFSuRAECI 9Ty6n+Z+Z9KzLSllkWEMdIguN0PCYDBSXbbkRXbo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Thomas Gleixner , Alexei Starovoitov , Sasha Levin Subject: [PATCH 5.4 133/388] bpf: Remove recursion prevention from rcu free callback Date: Tue, 29 Sep 2020 12:57:44 +0200 Message-Id: <20200929110016.910998769@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200929110010.467764689@linuxfoundation.org> References: <20200929110010.467764689@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Thomas Gleixner [ 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 039d64b1bfb7d..728ffec52cf36 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)