From patchwork Thu Aug 5 14:05:15 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tatsuhiko Yasumatsu X-Patchwork-Id: 493264 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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 19AD9C432BE for ; Thu, 5 Aug 2021 14:07:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 020B96113E for ; Thu, 5 Aug 2021 14:07:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241855AbhHEOIC (ORCPT ); Thu, 5 Aug 2021 10:08:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37292 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239887AbhHEOIA (ORCPT ); Thu, 5 Aug 2021 10:08:00 -0400 Received: from mail-pj1-x102f.google.com (mail-pj1-x102f.google.com [IPv6:2607:f8b0:4864:20::102f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 91EDAC061765; Thu, 5 Aug 2021 07:07:45 -0700 (PDT) Received: by mail-pj1-x102f.google.com with SMTP id u13-20020a17090abb0db0290177e1d9b3f7so15072025pjr.1; Thu, 05 Aug 2021 07:07:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=OibPOHM4csfd5W9jXrElMvcVRfnZS6gDVVfoFCeSUOI=; b=BVuGKKHnUlwvm+fNGyv2t1uabrBpZuVRIaJvS/V7uR4Hsfspd77wayaNwI3LvSJ6qk mYMltcw12BRXxY8FPF9M9JR2p+H7A5x7iaD8c+2Lkdlt3SYIaQICLEgJybUxtoaI8Q5W nCAen9+yaNXxdLna9VdqvtGm9L4hsKgRkMrphhPDkBDVJlNEMQKjLh9tHqljySEwlatU 8QcbMaVHlIF6on0byMk08kt5VDYBRiFzgIsUbZLiOWlLYajfqFv8lHsKQ3xYxqoC0hdH T8+riozdQgYYzDyy6zPATqR0DcZa1MovepWN06sbCUdye2gW5ef3m3aF9wNf6XfxbfVj RUAw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=OibPOHM4csfd5W9jXrElMvcVRfnZS6gDVVfoFCeSUOI=; b=EtXgCi7Mgn2PKnx9VvrW63/s/JRzBY/Ok7Jo/8PqkdLmq4C1KY+iDLl2bpBVLBMpfK JmnPz+Y2J2bCZ2DPJlJ4CS8GAQedgvDbeuOcYFSg/E2cCT+Lx9pEC6hRsratjxetRRjN 85AfvWiFcd2XARRlADKxThTEDrf6CPywUxUtGTFDgln+5aU0/lI1Hyfn5yEdtPatqx0P id3U0O0PkmYBQcs+ZzrGR8sDflJ0f/baa0GCtgavHq0Y4ZlUPEcp4VMA5X3hW2QgGDBL qKSt/FazUrdoUZSKsI4BNXiireb78FfiTwcZn0fz4ifvCzy2uZQJ4Xj3Ax9DBNcPKp1X /0fw== X-Gm-Message-State: AOAM533kCl9e31CuCuT2uDnsMKfBhSYw5E9eAYcquZlRRaLhYrsz8zv+ 8rXZxSdNxGxy4f2qG5M5zzs= X-Google-Smtp-Source: ABdhPJwullE2U2YB4rB8fXaVU00zqEu67SeTVjhu1pKKItUzNZFPjttiUIylxx/1wTB+JW7yVq2CKg== X-Received: by 2002:a63:e14c:: with SMTP id h12mr510070pgk.431.1628172465075; Thu, 05 Aug 2021 07:07:45 -0700 (PDT) Received: from localhost.localdomain ([240b:11:82a2:3000:45ab:3f64:7350:39b4]) by smtp.gmail.com with ESMTPSA id y12sm8682892pgk.7.2021.08.05.07.07.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Aug 2021 07:07:44 -0700 (PDT) From: Tatsuhiko Yasumatsu To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko Cc: th.yasumatsu@gmail.com, Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] bpf: Fix integer overflow involving bucket_size Date: Thu, 5 Aug 2021 23:05:15 +0900 Message-Id: <20210805140515.35630-1-th.yasumatsu@gmail.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org In __htab_map_lookup_and_delete_batch(), hash buckets are iterated over to count the number of elements in each bucket (bucket_size). If bucket_size is large enough, the multiplication to calculate kvmalloc() size could overflow, resulting in out-of-bounds write as reported by KASAN. [...] [ 104.986052] BUG: KASAN: vmalloc-out-of-bounds in __htab_map_lookup_and_delete_batch+0x5ce/0xb60 [ 104.986489] Write of size 4194224 at addr ffffc9010503be70 by task crash/112 [ 104.986889] [ 104.987193] CPU: 0 PID: 112 Comm: crash Not tainted 5.14.0-rc4 #13 [ 104.987552] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 [ 104.988104] Call Trace: [ 104.988410] dump_stack_lvl+0x34/0x44 [ 104.988706] print_address_description.constprop.0+0x21/0x140 [ 104.988991] ? __htab_map_lookup_and_delete_batch+0x5ce/0xb60 [ 104.989327] ? __htab_map_lookup_and_delete_batch+0x5ce/0xb60 [ 104.989622] kasan_report.cold+0x7f/0x11b [ 104.989881] ? __htab_map_lookup_and_delete_batch+0x5ce/0xb60 [ 104.990239] kasan_check_range+0x17c/0x1e0 [ 104.990467] memcpy+0x39/0x60 [ 104.990670] __htab_map_lookup_and_delete_batch+0x5ce/0xb60 [ 104.990982] ? __wake_up_common+0x4d/0x230 [ 104.991256] ? htab_of_map_free+0x130/0x130 [ 104.991541] bpf_map_do_batch+0x1fb/0x220 [...] In hashtable, if the elements' keys have the same jhash() value, the elements will be put into the same bucket. By putting a lot of elements into a single bucket, the value of bucket_size can be increased to trigger the integer overflow. Triggering the overflow is possible for both callers with CAP_SYS_ADMIN and callers without CAP_SYS_ADMIN. It will be trivial for a caller with CAP_SYS_ADMIN to intentionally reach this overflow by enabling BPF_F_ZERO_SEED. As this flag will set the random seed passed to jhash() to 0, it will be easy for the caller to prepare keys which will be hashed into the same value, and thus put all the elements into the same bucket. If the caller does not have CAP_SYS_ADMIN, BPF_F_ZERO_SEED cannot be used. However, it will be still technically possible to trigger the overflow, by guessing the random seed value passed to jhash() (32bit) and repeating the attempt to trigger the overflow. In this case, the probability to trigger the overflow will be low and will take a very long time. Fix the integer overflow by casting 1 operand to u64. Fixes: 057996380a42 ("bpf: Add batch ops to all htab bpf map") Signed-off-by: Tatsuhiko Yasumatsu --- 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 72c58cc516a3..e29283c3b17f 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -1565,8 +1565,8 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map, /* We cannot do copy_from_user or copy_to_user inside * the rcu_read_lock. Allocate enough space here. */ - keys = kvmalloc(key_size * bucket_size, GFP_USER | __GFP_NOWARN); - values = kvmalloc(value_size * bucket_size, GFP_USER | __GFP_NOWARN); + keys = kvmalloc((u64)key_size * bucket_size, GFP_USER | __GFP_NOWARN); + values = kvmalloc((u64)value_size * bucket_size, GFP_USER | __GFP_NOWARN); if (!keys || !values) { ret = -ENOMEM; goto after_loop;