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 X-Spam-Level: X-Spam-Status: No, score=-2.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 D574BC433E0 for ; Tue, 16 Feb 2021 10:04:33 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4408864DDA for ; Tue, 16 Feb 2021 10:04:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4408864DDA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 964FB8D0169; Tue, 16 Feb 2021 05:04:32 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 912CA8D0140; Tue, 16 Feb 2021 05:04:32 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 801C98D0169; Tue, 16 Feb 2021 05:04:32 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0222.hostedemail.com [216.40.44.222]) by kanga.kvack.org (Postfix) with ESMTP id 64D298D0140 for ; Tue, 16 Feb 2021 05:04:32 -0500 (EST) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 37F35348D for ; Tue, 16 Feb 2021 10:04:32 +0000 (UTC) X-FDA: 77823696384.07.room24_501415127642 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin07.hostedemail.com (Postfix) with ESMTP id 1B9341803F9B7 for ; Tue, 16 Feb 2021 10:04:32 +0000 (UTC) X-HE-Tag: room24_501415127642 X-Filterd-Recvd-Size: 8333 Received: from mail-il1-f173.google.com (mail-il1-f173.google.com [209.85.166.173]) by imf16.hostedemail.com (Postfix) with ESMTP for ; Tue, 16 Feb 2021 10:04:31 +0000 (UTC) Received: by mail-il1-f173.google.com with SMTP id d20so7826793ilo.4 for ; Tue, 16 Feb 2021 02:04:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=Mz0DGdMjzic+Z5818lQgZsXyz6D0ia8qb6rrQBhtrig=; b=TtKU9O1kMEZQ92eXOuPAZOph+m+SDW4ClQPT0Tbm0pn+YsqEQTjwiZ/H3beWjq9jVE wJgM7C532e54Q6pzRbrTW8updXrKSi+LtC369R2CQEughn9qrs+BwsZtNlWGi5z5fRjW GawPSpZH4xqCzQ20Wu7Nfx4xc8mC1U8/dPDpAUCDjMRHRZoemsYZ0vg6BtO/7WJBQx6U +mqMfPch6LaN4Viv241zFR5sCu43bncWYyxfkEcjhC/l+uKR3f0E9+Qcyz0YsaOnOqhu 9Qm95Rb5q9mEVLcfXlVhGPnq01aZis5eyKB+qEspDnWqZsJbvQahFCA9mZ8jZeiL02zQ t8/A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=Mz0DGdMjzic+Z5818lQgZsXyz6D0ia8qb6rrQBhtrig=; b=dJEseBZ8l0Yn+iUjsoqPV2eYE/DisA91wRFLdMY9c//mzOKnLZgOZkRx43KQDV/T18 dbhhzkSUhnUs6a9hzAWm2SGZ910REbZ4PEt/5Oi5xrUvigQBgyPIFcCDbC2VUxRUb0TC AeGDAPJGKAajcmd31G6pEZroXGcluwujSRgND+QVnHixfc6m6RpGyg4LVsWZQKpCe1FM PYr79VMFVCfvC2LjdTagcZsbJxwr+AcQqMsI3CuzHjnXeLrenUeQDVWKMegGKSFSJGtT OnDJJFBivogBUEFfftwe4S9K4srSppdhss0uNkMYhoJZnlMd7/xew4k2bt+MabjGUgFc S7GQ== X-Gm-Message-State: AOAM532o2H5WLbezMfNyCKDbbAMoqW6rvNtoc5DRBVyQhlASAluV+YxS vrcjC0Q4dalbs10SDC1lCCTbenVr2wJ726ta6yI= X-Google-Smtp-Source: ABdhPJxtwuMwouBVCpFXNSADxXIhbOlzhD8XtrJAU8tKlNXtZf5cqv4Jc7lMhETNwW/nft1mmuckFJFRA/lFOcVcGTs= X-Received: by 2002:a05:6e02:1bee:: with SMTP id y14mr16449921ilv.256.1613469870951; Tue, 16 Feb 2021 02:04:30 -0800 (PST) MIME-Version: 1.0 References: <8c4f1cb7c51b03d2b2cd451a6404db8e269d94b7.1613465062.git.tommyhebb@gmail.com> In-Reply-To: From: Tom Hebb Date: Tue, 16 Feb 2021 02:04:20 -0800 Message-ID: Subject: Re: [RFC PATCH] z3fold: prevent reclaim/free race for headless pages To: Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, Andrew Morton , Vitaly Wool , linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Feb 16, 2021 at 1:21 AM Greg Kroah-Hartman wrote: > > On Tue, Feb 16, 2021 at 12:44:40AM -0800, Thomas Hebb wrote: > > commit ca0246bb97c2 ("z3fold: fix possible reclaim races") introduced > > the PAGE_CLAIMED flag "to avoid racing on a z3fold 'headless' page > > release." By atomically testing and setting the bit in each of > > z3fold_free() and z3fold_reclaim_page(), a double-free was avoided. > > > > However, commit 746d179b0e66 ("z3fold: stricter locking and more carefu= l > > reclaim") appears to have unintentionally broken this behavior by movin= g > > the PAGE_CLAIMED check in z3fold_reclaim_page() to after the page lock > > gets taken, which only happens for non-headless pages. For headless > > pages, the check is now skipped entirely and races can occur again. > > > > I have observed such a race on my system: > > > > page:00000000ffbd76b7 refcount:0 mapcount:0 mapping:000000000000000= 0 index:0x0 pfn:0x165316 > > flags: 0x2ffff0000000000() > > raw: 02ffff0000000000 ffffea0004535f48 ffff8881d553a170 00000000000= 00000 > > raw: 0000000000000000 0000000000000011 00000000ffffffff 00000000000= 00000 > > page dumped because: VM_BUG_ON_PAGE(page_ref_count(page) =3D=3D 0) > > ------------[ cut here ]------------ > > kernel BUG at include/linux/mm.h:707! > > invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI > > CPU: 2 PID: 291928 Comm: kworker/2:0 Tainted: G B 5.= 10.7-arch1-1-kasan #1 > > Hardware name: Gigabyte Technology Co., Ltd. H97N-WIFI/H97N-WIFI, B= IOS F9b 03/03/2016 > > Workqueue: zswap-shrink shrink_worker > > RIP: 0010:__free_pages+0x10a/0x130 > > Code: c1 e7 06 48 01 ef 45 85 e4 74 d1 44 89 e6 31 d2 41 83 ec 01 e= 8 e7 b0 ff ff eb da 48 c7 c6 e0 32 91 88 48 89 ef e8 a6 89 f8 ff <0f> 0b 4c= 89 e7 e8 fc 79 07 00 e9 33 ff ff ff 48 89 ef e8 ff 79 07 > > RSP: 0000:ffff88819a2ffb98 EFLAGS: 00010296 > > RAX: 0000000000000000 RBX: ffffea000594c5a8 RCX: 0000000000000000 > > RDX: 1ffffd4000b298b7 RSI: 0000000000000000 RDI: ffffea000594c5b8 > > RBP: ffffea000594c580 R08: 000000000000003e R09: ffff8881d5520bbb > > R10: ffffed103aaa4177 R11: 0000000000000001 R12: ffffea000594c5b4 > > R13: 0000000000000000 R14: ffff888165316000 R15: ffffea000594c588 > > FS: 0000000000000000(0000) GS:ffff8881d5500000(0000) knlGS:0000000= 000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 00007f7c8c3654d8 CR3: 0000000103f42004 CR4: 00000000001706e0 > > Call Trace: > > z3fold_zpool_shrink+0x9b6/0x1240 > > ? sugov_update_single+0x357/0x990 > > ? sched_clock+0x5/0x10 > > ? sched_clock_cpu+0x18/0x180 > > ? z3fold_zpool_map+0x490/0x490 > > ? _raw_spin_lock_irq+0x88/0xe0 > > shrink_worker+0x35/0x90 > > process_one_work+0x70c/0x1210 > > ? pwq_dec_nr_in_flight+0x15b/0x2a0 > > worker_thread+0x539/0x1200 > > ? __kthread_parkme+0x73/0x120 > > ? rescuer_thread+0x1000/0x1000 > > kthread+0x330/0x400 > > ? __kthread_bind_mask+0x90/0x90 > > ret_from_fork+0x22/0x30 > > Modules linked in: rfcomm ebtable_filter ebtables ip6table_filter i= p6_tables iptable_filter ccm algif_aead des_generic libdes ecb algif_skciph= er cmac bnep md4 algif_hash af_alg vfat fat intel_rapl_msr intel_rapl_commo= n x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel iwlmvm hid_logit= ech_hidpp kvm at24 mac80211 snd_hda_codec_realtek iTCO_wdt snd_hda_codec_ge= neric intel_pmc_bxt snd_hda_codec_hdmi ledtrig_audio iTCO_vendor_support me= i_wdt mei_hdcp snd_hda_intel snd_intel_dspcfg libarc4 soundwire_intel irqby= pass iwlwifi soundwire_generic_allocation rapl soundwire_cadence intel_csta= te snd_hda_codec intel_uncore btusb joydev mousedev snd_usb_audio pcspkr bt= rtl uvcvideo nouveau btbcm i2c_i801 btintel snd_hda_core videobuf2_vmalloc = i2c_smbus snd_usbmidi_lib videobuf2_memops bluetooth snd_hwdep soundwire_bu= s snd_soc_rt5640 videobuf2_v4l2 cfg80211 snd_soc_rl6231 videobuf2_common sn= d_rawmidi lpc_ich alx videodev mdio snd_seq_device snd_soc_core mc ecdh_gen= eric mxm_wmi mei_me > > hid_logitech_dj wmi snd_compress e1000e ac97_bus mei ttm rfkill sn= d_pcm_dmaengine ecc snd_pcm snd_timer snd soundcore mac_hid acpi_pad pkcs8_= key_parser it87 hwmon_vid crypto_user fuse ip_tables x_tables ext4 crc32c_g= eneric crc16 mbcache jbd2 dm_crypt cbc encrypted_keys trusted tpm rng_core = usbhid dm_mod crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_inte= l aesni_intel crypto_simd cryptd glue_helper xhci_pci xhci_pci_renesas i915= video intel_gtt i2c_algo_bit drm_kms_helper syscopyarea sysfillrect sysimg= blt fb_sys_fops cec drm agpgart > > ---[ end trace 126d646fc3dc0ad8 ]--- > > > > To fix the issue, re-add the earlier test and set in the case where we > > have a headless page. > > > > Fixes: 746d179b0e66 ("z3fold: stricter locking and more careful reclaim= ") > > This commit id is not in Linus's tree :( Oops, I was building from a 5.10 stable tree and accidentally grabbed the ID of the pick there. This is the correct line, will fix in v1: Fixes: dcf5aedb24f8 ("z3fold: stricter locking and more careful reclaim") (And sorry for my initial failure to reply-all; I contribute to projects that use mailing lists just infrequently enough for me to forget all the common mistakes, meaning I repeat them every time.) > thanks, > > greg k-h