From patchwork Thu Sep 16 15:59:26 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 513872 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=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, 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 A35C3C433F5 for ; Thu, 16 Sep 2021 16:51:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 91BA0615E1 for ; Thu, 16 Sep 2021 16:51:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244825AbhIPQwn (ORCPT ); Thu, 16 Sep 2021 12:52:43 -0400 Received: from mail.kernel.org ([198.145.29.99]:36672 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345702AbhIPQui (ORCPT ); Thu, 16 Sep 2021 12:50:38 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id A4A6A615E1; Thu, 16 Sep 2021 16:28:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1631809702; bh=HHzXryoclVb28PAEcdGV2ae0lvs1Y5+1rSLNsbTxRDc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0nDYLLM8YkCoEk+llQd++7nKwANjq6Uop/jAG8mE1HrwhYBE3B1Xxg6S/zVkFHrIk rUqJT+CY1tadZ8EeYLwveEp/3nRoCMrAZsq1LdnylHQEZZVC+zTIC9pqd0fgiM7DTf 71GxOKV8j0G85kE2quWTe3xKAyFXDXinObIog3DI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Martynas Pumputis , Andrii Nakryiko , Sasha Levin Subject: [PATCH 5.13 209/380] libbpf: Fix race when pinning maps in parallel Date: Thu, 16 Sep 2021 17:59:26 +0200 Message-Id: <20210916155811.188893140@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210916155803.966362085@linuxfoundation.org> References: <20210916155803.966362085@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Martynas Pumputis [ Upstream commit 043c5bb3c4f43670ab4fea0b847373ab42d25f3e ] When loading in parallel multiple programs which use the same to-be pinned map, it is possible that two instances of the loader will call bpf_object__create_maps() at the same time. If the map doesn't exist when both instances call bpf_object__reuse_map(), then one of the instances will fail with EEXIST when calling bpf_map__pin(). Fix the race by retrying reusing a map if bpf_map__pin() returns EEXIST. The fix is similar to the one in iproute2: e4c4685fd6e4 ("bpf: Fix race condition with map pinning"). Before retrying the pinning, we don't do any special cleaning of an internal map state. The closer code inspection revealed that it's not required: - bpf_object__create_map(): map->inner_map is destroyed after a successful call, map->fd is closed if pinning fails. - bpf_object__populate_internal_map(): created map elements is destroyed upon close(map->fd). - init_map_slots(): slots are freed after their initialization. Signed-off-by: Martynas Pumputis Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20210726152001.34845-1-m@lambda.lt Signed-off-by: Sasha Levin --- tools/lib/bpf/libbpf.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index c4d36328069c..533512d933c6 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -4570,10 +4570,13 @@ bpf_object__create_maps(struct bpf_object *obj) char *cp, errmsg[STRERR_BUFSIZE]; unsigned int i, j; int err; + bool retried; for (i = 0; i < obj->nr_maps; i++) { map = &obj->maps[i]; + retried = false; +retry: if (map->pin_path) { err = bpf_object__reuse_map(map); if (err) { @@ -4581,6 +4584,12 @@ bpf_object__create_maps(struct bpf_object *obj) map->name); goto err_out; } + if (retried && map->fd < 0) { + pr_warn("map '%s': cannot find pinned map\n", + map->name); + err = -ENOENT; + goto err_out; + } } if (map->fd >= 0) { @@ -4614,9 +4623,13 @@ bpf_object__create_maps(struct bpf_object *obj) if (map->pin_path && !map->pinned) { err = bpf_map__pin(map, NULL); if (err) { + zclose(map->fd); + if (!retried && err == -EEXIST) { + retried = true; + goto retry; + } pr_warn("map '%s': failed to auto-pin at '%s': %d\n", map->name, map->pin_path, err); - zclose(map->fd); goto err_out; } }