From mboxrd@z Thu Jan 1 00:00:00 1970 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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6D8D5C61DA4 for ; Tue, 14 Feb 2023 16:09:11 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pRxrR-0001BG-Ni; Tue, 14 Feb 2023 11:08:53 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pRxrQ-00019t-CF for qemu-devel@nongnu.org; Tue, 14 Feb 2023 11:08:52 -0500 Received: from mail-wr1-x432.google.com ([2a00:1450:4864:20::432]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1pRxrO-0002SY-BO for qemu-devel@nongnu.org; Tue, 14 Feb 2023 11:08:52 -0500 Received: by mail-wr1-x432.google.com with SMTP id h16so16174825wrz.12 for ; Tue, 14 Feb 2023 08:08:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=xVSCeYOyMug0x9LmE6mrm+Kpn6VeDGJ6hpmmyfOxL8M=; b=GUYsgCKoSpTVHTMVSQN5wlErbFKtRrg/4ta6lgXNQEoq9VOBxfX9IwYK6hv+QH+pgE pH4e37vIeiuC56cb1LPVVIdR5L8gq1imrIJrUKvRFyNh6I+o4WcMIANpH9wPDwrk0oJa VpCElS9h/djzM3ES+AQXiWiIRSjAG0sy1mofmsGNZf1alElKgyjRIwy3RTDTLBeEgtA8 y7NoELvXytA8K1wgnrWcL+mtcxzypbooZr/zp9zMI+UCh0iIKGj/0THdj1REoYV6G44G hNIFV1aFzfD1/aAxH7dfdKasR/voX1G2tkj2Z5gQGM1BUwzjBPVbEcywdx4DxcpNPSkR DdVw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=xVSCeYOyMug0x9LmE6mrm+Kpn6VeDGJ6hpmmyfOxL8M=; b=wsGMkMPwatpzMxkh3pHznNvTc5hBXePZO6IDoyxYI4BzyRPAM4rEC3Xts9q6JfUktd AOAchuZjsIJHu/ZFjejfuOVY2tgR89oSpZn021wdfh3F2+8syFsjMM5SsNb/RMt/02cg 6zV8D0EAv8EF5hqW3ZMiVSBfnnGp2FdsWP194vouObIhpDfKBbW4pleUIXTJ7yLw25XS lL3zgGZBywpONkg4lG1xx/9VtIPiCB8WBIWznWny0g5oV2YcxP5wYVoNtPuZ25bK+W5Q Cep870mIUznBXA0BeykDag2fMDAuHU8wchGOgLlwMfF2VEFR5qxK1lEC34rrEz/X/d8A Sm4Q== X-Gm-Message-State: AO0yUKU8l6hCZTrUka0rrJ8GRqipb/a9zGE6o4S4IB2EYwJz0L4RjhLU DunQJwONLu+kFhRGmQFTPhueJw== X-Google-Smtp-Source: AK7set+XFofX2eM96Rx3kuZQIuUg/4PZSAJilarrTVsPA0Yh3lXDqLvOFS+Qqif5iYV+5agjOkyG1Q== X-Received: by 2002:adf:ec06:0:b0:2c5:617f:e348 with SMTP id x6-20020adfec06000000b002c5617fe348mr80775wrn.25.1676390928677; Tue, 14 Feb 2023 08:08:48 -0800 (PST) Received: from [192.168.30.216] ([81.0.6.76]) by smtp.gmail.com with ESMTPSA id b4-20020a5d4d84000000b002c5621263e3sm2406041wru.19.2023.02.14.08.08.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 14 Feb 2023 08:08:48 -0800 (PST) Message-ID: Date: Tue, 14 Feb 2023 17:08:46 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.7.2 Subject: Re: [PATCH 00/10] Retire Fork-Based Fuzzing Content-Language: en-US To: Stefan Hajnoczi , Alexander Bulekov Cc: qemu-devel@nongnu.org, Bandan Das , Darren Kenny , Paolo Bonzini , Laurent Vivier , Thomas Huth References: <20230205042951.3570008-1-alxndr@bu.edu> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::432; envelope-from=philmd@linaro.org; helo=mail-wr1-x432.google.com X-Spam_score_int: -4 X-Spam_score: -0.5 X-Spam_bar: / X-Spam_report: (-0.5 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.35, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URI_DOTEDU=1.999 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 14/2/23 16:38, Stefan Hajnoczi wrote: > On Sat, Feb 04, 2023 at 11:29:41PM -0500, Alexander Bulekov wrote: >> Hello, >> This series removes fork-based fuzzing. >> How does fork-based fuzzing work? >> * A single parent process initializes QEMU >> * We identify the devices we wish to fuzz (fuzzer-dependent) >> * Use QTest to PCI enumerate the devices >> * After that we start a fork-server which forks the process and executes >> fuzzer inputs inside the disposable children. >> >> In a normal fuzzing process, everything happens in a single process. >> >> Pros of fork-based fuzzing: >> * We only need to do common configuration once (e.g. PCI enumeration). >> * Fork provides a strong guarantee that fuzzer inputs will not interfere with >> each-other >> * The fuzzing process can continue even after a child-process crashes >> * We can apply our-own timers to child-processes to exit slow inputs, early >> >> Cons of fork-based fuzzing: >> * Fork-based fuzzing is not supported by libfuzzer. We had to build our own >> fork-server and rely on tricks using linker-scripts and shared-memory to >> support fuzzing. ( https://physics.bu.edu/~alxndr/libfuzzer-forkserver/ ) >> * Fork-based fuzzing is currently the main blocker preventing us from enabling >> other fuzzers such as AFL++ on OSS-Fuzz >> * Fork-based fuzzing may be a reason why coverage-builds are failing on >> OSS-Fuzz. Coverage is an important fuzzing metric which would allow us to >> find parts of the code that are not well-covered. >> * Fork-based fuzzing has high overhead. fork() is an expensive system-call, >> especially for processes running ASAN (with large/complex) VMA layouts. >> * Fork prevents us from effectively fuzzing devices that rely on >> threads (e.g. qxl). >> >> These patches remove fork-based fuzzing and replace it with reboot-based >> fuzzing for most cases. Misc notes about this change: >> * libfuzzer appears to be no longer in active development. As such, the >> current implementation of fork-based fuzzing (while having some nice >> advantages) is likely to hold us back in the future. If these changes >> are approved and appear to run successfully on OSS-Fuzz, we should be >> able to easily experiment with other fuzzing engines (AFL++). >> * Some device do not completely reset their state. This can lead to >> non-reproducible crashes. However, in my local tests, most crashes >> were reproducible. OSS-Fuzz shouldn't send us reports unless it can >> consistently reproduce a crash. >> * In theory, the corpus-format should not change, so the existing >> corpus-inputs on OSS-Fuzz will transfer to the new reset()-able >> fuzzers. >> * Each fuzzing process will now exit after a single crash is found. To >> continue the fuzzing process, use libfuzzer flags such as -jobs=-1 >> * We no long control input-timeouts (those are handled by libfuzzer). >> Since timeouts on oss-fuzz can be many seconds long, I added a limit >> on the number of DMA bytes written. >> >> >> Alexander Bulekov (10): >> hw/sparse-mem: clear memory on reset >> fuzz: add fuzz_reboot API >> fuzz/generic-fuzz: use reboots instead of forks to reset state >> fuzz/generic-fuzz: add a limit on DMA bytes written >> fuzz/virtio-scsi: remove fork-based fuzzer >> fuzz/virtio-net: remove fork-based fuzzer >> fuzz/virtio-blk: remove fork-based fuzzer >> fuzz/i440fx: remove fork-based fuzzer >> fuzz: remove fork-fuzzing scaffolding >> docs/fuzz: remove mentions of fork-based fuzzing >> >> docs/devel/fuzzing.rst | 22 +----- >> hw/mem/sparse-mem.c | 13 +++- >> meson.build | 4 - >> tests/qtest/fuzz/fork_fuzz.c | 41 ---------- >> tests/qtest/fuzz/fork_fuzz.h | 23 ------ >> tests/qtest/fuzz/fork_fuzz.ld | 56 -------------- >> tests/qtest/fuzz/fuzz.c | 6 ++ >> tests/qtest/fuzz/fuzz.h | 2 +- >> tests/qtest/fuzz/generic_fuzz.c | 111 +++++++--------------------- >> tests/qtest/fuzz/i440fx_fuzz.c | 27 +------ >> tests/qtest/fuzz/meson.build | 6 +- >> tests/qtest/fuzz/virtio_blk_fuzz.c | 51 ++----------- >> tests/qtest/fuzz/virtio_net_fuzz.c | 54 ++------------ >> tests/qtest/fuzz/virtio_scsi_fuzz.c | 51 ++----------- >> 14 files changed, 72 insertions(+), 395 deletions(-) >> delete mode 100644 tests/qtest/fuzz/fork_fuzz.c >> delete mode 100644 tests/qtest/fuzz/fork_fuzz.h >> delete mode 100644 tests/qtest/fuzz/fork_fuzz.ld >> >> -- >> 2.39.0 >> > > Whose tree should this go through? Laurent's qtest tree? Do you mean Thomas? $ git shortlog -cs tests/qtest/fuzz | sort -rn 32 Thomas Huth 26 Paolo Bonzini 19 Stefan Hajnoczi 6 Markus Armbruster 5 Alexander Bulekov 4 Marc-André Lureau 3 Peter Maydell 2 Laurent Vivier 1 Michael S. Tsirkin 1 Gerd Hoffmann In doubt, cc'ing both :) > Acked-by: Stefan Hajnoczi