From patchwork Sat Dec 17 15:02:06 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tonghao Zhang X-Patchwork-Id: 13075845 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C6CD6C4332F for ; Sat, 17 Dec 2022 15:02:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229613AbiLQPCW (ORCPT ); Sat, 17 Dec 2022 10:02:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54930 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229704AbiLQPCS (ORCPT ); Sat, 17 Dec 2022 10:02:18 -0500 Received: from mail-pf1-x42d.google.com (mail-pf1-x42d.google.com [IPv6:2607:f8b0:4864:20::42d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BABD2E0D3 for ; Sat, 17 Dec 2022 07:02:16 -0800 (PST) Received: by mail-pf1-x42d.google.com with SMTP id a14so3596701pfa.1 for ; Sat, 17 Dec 2022 07:02:16 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=ac34a4260OiGhUdPdxmE/Jcjul2AuDI7xA9NMT5T/gM=; b=fRZfDLwU5m1extAUTZYVjRN5Wg6tDFda1KGXRuXXKy0Oy+uav0+UCa4CZgjQ0QLatC 0GnvnOC3hOdgnT7GND/TqjHlmUduM6mFYw9NDOUigLLuuJUZzYcjwEsdxcnVz6dKBC+S yjZjR7S2fUV0qwABvawSCeSmqs4VpISn3m+WbqDdDxZLZAYKeNkhCiDm3TmNVbtyFNE4 vQOiEoQ51rVsEFiV/8cze/J2N601PxZSZzcAUbXjYvs6Ms33Mr9MBa7WySZX2/TOqWvK 3AdZPh+KzZ5j5lAvteF6PsVVMo35ay7xPeduscv5iecA/GcDIv5jz2nGgyCbJrQAJHUV kCEg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=ac34a4260OiGhUdPdxmE/Jcjul2AuDI7xA9NMT5T/gM=; b=7raica8ntcyh33ZhSChaiTpNV6Ej3V3OrdwEIzoBZFIfqe7mSjOH6B6S8cCdw4Qdi0 8q8rvanacht3SA6HZTQVtpW04b1ZgzdNrn6X2PxDESrl5oZyM9cP+3hBEfZunWFxBnx4 zFibv37zCmTKo1lRIgkxiguZxT8avQwU1cvFUUT2XvXfmENrM8yP2XGMipcgybA7YKT/ i8VDUX5fu2aMPa6Vd0Nre7+nhYi68XBT7hcIG1z83lDuEDjbmZIuRZw34VN6Q4VaO7uL c2FT3MDECKGvwsriTADaE6oufX2JG6Q2rjAn+NXdRI0mD0Nes2pq/9LV0Wacoe74wTTs UkyA== X-Gm-Message-State: ANoB5plTIFUu+5cQFur2bh0pSSnsDoCEzHn29G8Ih8vBDs9txBC8/f3r V4SA+O98uprxSskjrM3NCU//MaankJZ+uw== X-Google-Smtp-Source: AA0mqf5OjFZgW8PFyPqqNsaW3ehvPlSdTpgv/QNUtmtEPlQ0fbcC1Z4o9KEB7aVB5hwO9Zd1H39vdg== X-Received: by 2002:aa7:91c5:0:b0:566:900d:a1cd with SMTP id z5-20020aa791c5000000b00566900da1cdmr33181903pfa.9.1671289335803; Sat, 17 Dec 2022 07:02:15 -0800 (PST) Received: from bogon.xiaojukeji.com ([111.201.145.40]) by smtp.gmail.com with ESMTPSA id s17-20020aa78bd1000000b00576ebde78ffsm3250880pfd.192.2022.12.17.07.02.11 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sat, 17 Dec 2022 07:02:14 -0800 (PST) From: xiangxia.m.yue@gmail.com To: bpf@vger.kernel.org Cc: Tonghao Zhang , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Hou Tao Subject: [bpf-next v2 1/2] bpf: hash map, avoid deadlock with suitable hash mask Date: Sat, 17 Dec 2022 23:02:06 +0800 Message-Id: <20221217150207.58577-1-xiangxia.m.yue@gmail.com> X-Mailer: git-send-email 2.30.1 (Apple Git-130) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net From: Tonghao Zhang The deadlock still may occur while accessed in NMI and non-NMI context. Because in NMI, we still may access the same bucket but with different map_locked index. For example, on the same CPU, .max_entries = 2, we update the hash map, with key = 4, while running bpf prog in NMI nmi_handle(), to update hash map with key = 20, so it will have the same bucket index but have different map_locked index. To fix this issue, using min mask to hash again. Signed-off-by: Tonghao Zhang Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: Andrii Nakryiko Cc: Martin KaFai Lau Cc: Song Liu Cc: Yonghong Song Cc: John Fastabend Cc: KP Singh Cc: Stanislav Fomichev Cc: Hao Luo Cc: Jiri Olsa Cc: Hou Tao Acked-by: Yonghong Song Acked-by: Hou Tao --- kernel/bpf/hashtab.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index 5aa2b5525f79..974f104f47a0 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -152,7 +152,7 @@ static inline int htab_lock_bucket(const struct bpf_htab *htab, { unsigned long flags; - hash = hash & HASHTAB_MAP_LOCK_MASK; + hash = hash & min_t(u32, HASHTAB_MAP_LOCK_MASK, htab->n_buckets -1); preempt_disable(); if (unlikely(__this_cpu_inc_return(*(htab->map_locked[hash])) != 1)) { @@ -171,7 +171,7 @@ static inline void htab_unlock_bucket(const struct bpf_htab *htab, struct bucket *b, u32 hash, unsigned long flags) { - hash = hash & HASHTAB_MAP_LOCK_MASK; + hash = hash & min_t(u32, HASHTAB_MAP_LOCK_MASK, htab->n_buckets -1); raw_spin_unlock_irqrestore(&b->raw_lock, flags); __this_cpu_dec(*(htab->map_locked[hash])); preempt_enable();