From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-lf1-f42.google.com (mail-lf1-f42.google.com [209.85.167.42]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9E5F73A7836 for ; Mon, 27 Apr 2026 14:45:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.42 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777301148; cv=none; b=s9khyevBCNnf71y+iGfLShMjx7Gb8ABbo+27z7yRRV2XEEbD2XnHgzTvlOAtz4mKdIfup4uf6tovmECS5FCZ1UQ3Qb38KfElGjeiyZptIT66wNq+JE+F8+SGc+rFsqAhwaNkOz6npFAxAyzk8HAFu5iRVMhcG4zwk1uc3r6cY38= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777301148; c=relaxed/simple; bh=q3aIvjod1hkwBWwjEQMOyxGraz9Cd8sLurUppc9iXOo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=C31N0P4/6A9VMuhxBEs1WD2aSMqmXGsbs1c95uP06avVH5PAQjkQovu2pOvWHwS6dtPrDGw82PJEiC4nV2Gq5Zk+wAVS9c0dutS4bFnxrpjryk0qTi72OqjYQ+UKAQp9bEDtFgUnZ+yOJcXDug2EGrEv3SMVnGEpRLXo7cvtTd8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=ao8boELJ; arc=none smtp.client-ip=209.85.167.42 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ao8boELJ" Received: by mail-lf1-f42.google.com with SMTP id 2adb3069b0e04-5a337552604so9283067e87.2 for ; Mon, 27 Apr 2026 07:45:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1777301145; x=1777905945; darn=vger.kernel.org; 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=q3aIvjod1hkwBWwjEQMOyxGraz9Cd8sLurUppc9iXOo=; b=ao8boELJct7l5U4NwJLHaf/JLkuHxhw0m/FZd5n27HkR/qiRpo3etdc1OLeAhN1SdK Auv9v+dBixywnGknzzx4xJnnjo4pYNwOFaeDCVbpDmQQuwma4tCLdMbr3cHEEOPZMS5J I+Io8acWGqnXujfVj+vPnxLxUGxBITjxcCoOCMYAKGGrBOA8u+YHTI3NpjA0n35CaGhe SVyZTTYmhcoqf5ntTxwwh6AHQMGd054i6IBv5DMAQA70MmEaT3uucezI3ErbMNGyYrkg DLl9CtMe3zw1IFDO3sj7T7Wf3U9em0JGsUpXxGrcN4qufbwbRCJ9lLoy+d4P1V+m11Il x8gw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1777301145; x=1777905945; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=q3aIvjod1hkwBWwjEQMOyxGraz9Cd8sLurUppc9iXOo=; b=R40/j7+MY7Z3Jn5TaKO6c9b0xDicztcfDqA8WaUCLrF98hORe4jCknwwkrXiN4rEgh IW2cB4kDiX/oGffeNeWTHp/41LfjhEcSodFpfp+OLTcNyXlJg6vvLh38na32CbC6J9dM XKGrOKb52oLzHfnv6t58+U4gSABEU6GThbPBjsXdbETNynBuG9N2Ok6MZlMKlVlJeZkt sLya3EGXx4IXL32dbqPHTGVnEY10/W5RXoGiQV/Kh8S3a1XsN3gGDDknYxk8StiseXvh dX0DsciOis404HdJxwF9lulvKqwXXaF8FthO1oq/Wu6Y1gL+qo/xIdAXJcOSUyVfvKq5 vbhg== X-Forwarded-Encrypted: i=1; AFNElJ+AajbBorDbWpW5D1gcOWc0wFeSAxgeuUt6tUvPX9DNlu2gSfdnWDCTTk3BIIP60oaGWvPRZmXRBd/s5dU=@vger.kernel.org X-Gm-Message-State: AOJu0YzxLRagCKBmInfkonDojPDhQy67ySEY41A34kFJyoV4B4TrbhmV bLuC52Vo19s2GGg2w7vrwyAt3pO6cXJJyqiglcaI3QiLI+zzsC2lMI45fXmHHg== X-Gm-Gg: AeBDievJLVSP8oB0YSqsjH8c7X8zk/URjrJLRBnm1c1K2BWNn1fmMS1TyIRbItppDCm oN2Y14bS9gg4YTgGwkGeDQk3b6HCrVsvP6R6oZ26pJQxmUREtCrTRaSloFnxoLJ/rKgZllZATDl QhjPKT/BLldn/UypjHmvO/9GHQLxmOWlFzvq1A8spRT96qWjPSLnLaHUc3XhoQKP1+TRTdxZvR9 y9WOtRRjBZ4Zgjs5zEGRY5QxrFUqhmeuBgmvs3Oy450YLRi6M9dLC38c/weIXFCYRcud9Iej+ZS QppXRo325khFvPrNK+n0qrqgYWRmmvj7CL8oIyiborqibPD1jsj+KgXq//ergrB+MkAQ+Y3qcN0 l3dU4wp9JyfoPnXGmdcCtXu+2kz9tQLzEHYx7ysQ7vbEai4OKKPpyJue4Jdi9A3hg+3nHFsxo9U pg7rMxlqmuIJtCsAcEUb0ASkOcUJn/V1hKISyVf4kagX/Csmlz X-Received: by 2002:a05:6512:124d:b0:5a4:304:43cc with SMTP id 2adb3069b0e04-5a4172bb851mr13268087e87.9.1777301144378; Mon, 27 Apr 2026 07:45:44 -0700 (PDT) Received: from [192.168.0.111] ([77.220.140.242]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a4187e7ad0sm8223836e87.58.2026.04.27.07.45.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Apr 2026 07:45:43 -0700 (PDT) Message-ID: <24d53360-52c7-452c-8b8c-3c94a8cab65a@gmail.com> Date: Mon, 27 Apr 2026 17:45:42 +0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: erofs pointer corruption and kernel crash Content-Language: ru To: Gao Xiang , Arseniy Krasnov Cc: linux-erofs@lists.ozlabs.org, linux-kernel@vger.kernel.org, kernel@salutedevices.com, Gao Xiang References: <4a2f3801-fac1-42fe-ae75-da315822e088@salutedevices.com> <2e916997-0557-45e7-831a-b436c07c5ba4@salutedevices.com> <97ca00c7-822d-4b57-9dc0-9b396049adc9@salutedevices.com> <8c0bdfab-dbf2-4f1e-8e2a-ce18f166d841@linux.alibaba.com> <2ca3c8c6-f3ed-40ca-8f5c-1b43df479ad7@salutedevices.com> <36cddf44-3e08-4a19-82ed-04ca178ffab5@linux.alibaba.com> <15702a84-ea4f-4d12-b9e5-a37a4c3bb014@salutedevices.com> From: Arseniy Krasnov In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 26.04.2026 14:42, Arseniy Krasnov wrote: > 25.04.2026 18:29, Gao Xiang пишет: >> Hi Arseniy, >> >> On 2026/4/13 15:20, Arseniy Krasnov wrote: >>> >>> 13.04.2026 10:08, Gao Xiang пишет: >>>> >>>> On 2026/4/11 23:10, Arseniy Krasnov wrote: >>>>> >>>>> 10.04.2026 18:41, Gao Xiang пишет: >>>>>> Hi Arseniy, >>>>>> >>>>>> On 2026/4/10 21:27, Arseniy Krasnov wrote: >>>>>>> >>>>>>> 10.04.2026 15:20, Gao Xiang пишет: >>>>>>>> >>>>>>>> On 2026/4/10 19:37, Arseniy Krasnov wrote: >>>>>>>> >>>>>>>> (drop unrelated folks since they all subscribed erofs mailing list) >>>>>>>> >>>>>>>>> >>>>>>>>> 10.04.2026 11:31, Gao Xiang wrote: >>>>>>>>>> Hi, >>>>>>>>>> >>>>>>>>>> On 2026/4/10 16:13, Arseniy Krasnov wrote: >>>> ... >>>> >>>>>>>>>> I need more informations to find some clues. >>>>>>>>> >>>>>>>>> >>>>>>>>> So reproduced again with this debug patch which adds magic to 'struct z_erofs_pcluster' and prints 'struct folio' >>>>>>>>> when pointer in 'private' is passed to 'erofs_onlinefolio_end()'. In short - 'private' points to 'struct z_erofs_pcluster'. >>>>>>>> First, erofs-utils 1.8.10 doesn't support `-E48bit`: >>>>>>>> only erofs-utils 1.9+ ship it as an experimental >>>>>>>> feature, see Changelog; so I think you're using >>>>>>>> modified erofs-utils 1.8.10: >>>>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs-utils.git/tree/ChangeLog >>>>>>>> >>>>>>>> ``` >>>>>>>> erofs-utils 1.9 >>>>>>>> >>>>>>>>     * This release includes the following updates: >>>>>>>>       - Add 48-bit layout support for larger filesystems (EXPERIMENTAL); >>>>>>>> ``` >>>>>>>> >>>>>>>> Second, I'm pretty sure this issue is related to >>>>>>>> experimenal `-E48bit`, and those information is >>>>>>>> not enough for me to find the root cause, so I >>>>>>>> need to find a way to reproduce myself: It may >>>>>>>> take time; you could debug yourself but I don't >>>>>>>> think it's an easy task if you don't quite familiar >>>>>>>> with the EROFS codebase. >>>>>>>> >>>>>>>> Anyway I really suggest if you need a rush solution >>>>>>>> for production, don't use `-E48bit + zstd` like >>>>>>>> this for now: try to use other options like >>>>>>>> `-zzstd -C65536 -Efragments` instead since those >>>>>>>> are common production choices. >>>>>>> Ok thanks for this advice! One more question: currently we use this options: >>>>>>> "zstd,22 --max-extent-bytes 65536 -E48bit". Ok we remove "zstd,22" and "E48bit", >>>>>>> but what about "--max-extent-bytes 65536" - is it considered stable option? >>>>>>> Or it is better to use your version: "-zzstd -C65536 -Efragments" ? >>>>>> I'm not sure how you find this >>>>>> "zstd,22 --max-extent-bytes 65536 -E48bit" combination. >>>>>> >>>>>> My suggestion based on production is that as long as >>>>>> you don't use `-zzstd` ++ `-E48bit`, it should be fine. >>>>>> >>>>>> If you need smaller images, I suggest: `-zlzma,9 -C65536 -Efragments` >>>>>> Or like Android, they all use `-zlz4hc`, >>>>>> Or zstd, but don't add `-E48bit`. >>>>>> >>>>>> As for "--max-extent-bytes 65536", it can be dropped >>>>>> since if `-E48bit` is not used, it only has negative >>>>>> impacts. >>>>>> >>>>>> In short, `-E48bit` + `-zzstd` + `--max-extent-bytes` >>>>>> enables new unaligned compression for zstd, but it's >>>>>> a relatively new feature, I still still some time to >>>>>> stablize it but my own time is limited and all things >>>>>> are always prioritized. >>>>> Ok, thanks for this advice! >>>> FYI, I can reproduce this issue locally with `-E48bit` >>>> on in 600s. >>>> >>>> I do think it's a `-E48bit` + zstd issue so >>>> non-`-E48bit` won't be impacted and I will find time >>>> to troubleshoot it this week. >>> Yes, without '-E48bit' we also can't reproduce it for entire weekend on several boards. No such panics. >> Can you check if the following informal patch resolves >> this issue?  I've checked it locally: >> >> diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c >> index 8a0b15511931..824ffe4b871c 100644 >> --- a/fs/erofs/zdata.c >> +++ b/fs/erofs/zdata.c >> @@ -1509,12 +1509,6 @@ static void z_erofs_fill_bio_vec(struct bio_vec *bvec, >>      DBG_BUGON(z_erofs_is_shortlived_page(bvec->bv_page)); >> >>      folio = page_folio(zbv.page); >> -    /* For preallocated managed folios, add them to page cache here */ >> -    if (folio->private == Z_EROFS_PREALLOCATED_FOLIO) { >> -        tocache = true; >> -        goto out_tocache; >> -    } >> - >>      mapping = READ_ONCE(folio->mapping); >>      /* >>       * File-backed folios for inplace I/Os are all locked steady, >> @@ -1527,6 +1521,12 @@ static void z_erofs_fill_bio_vec(struct bio_vec *bvec, >>          return; >>      } >> >> +    if (cmpxchg(&folio->private, Z_EROFS_PREALLOCATED_FOLIO, NULL) == >> +        Z_EROFS_PREALLOCATED_FOLIO) { >> +        tocache = true; >> +        goto out_tocache; >> +    } >> + >>      folio_lock(folio); >>      if (likely(folio->mapping == mc)) { >>          /* >> @@ -1546,14 +1546,8 @@ static void z_erofs_fill_bio_vec(struct bio_vec *bvec, >>              } >>              return; >>          } >> -        /* >> -         * Already linked with another pcluster, which only appears in >> -         * crafted images by fuzzers for now.  But handle this anyway. >> -         */ >> -        tocache = false;    /* use temporary short-lived pages */ >>      } else { >> -        DBG_BUGON(1); /* referenced managed folios can't be truncated */ >> -        tocache = true; >> +        DBG_BUGON(1);        /* referenced managed folios can't be truncated */ >>      } >>      folio_unlock(folio); >>      folio_put(folio); >> >> >> I will form a formal patch later with comments and commit >> message later. > > Hi, thanks! I'll test it! Just tested this patch. Looks like problem is fixed in my reproducer! Thanks! > > >> Thanks, >> Gao Xiang