From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7BC23EAFA for ; Sun, 25 Feb 2024 10:45:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708857949; cv=none; b=WRdvRjNbxHeQaXftBu1Mcd9TcGNLli2xQNOFRvf9CN86wrsSpmR0qWSK9yxZi4ka2w41POci5RaMrhQSo2aW2XVWE2rF7KS1xvtuszKCTnX1Qv5St3Gi0GdMf9qJ8WSK6fqqpNda0AeqJm+7KPmODxUg/qlgXzFhG2M0ntvCWn8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708857949; c=relaxed/simple; bh=xaEEwq+zhwXXlXUsjzZ1qKHdigMxUKVoFzGsp+eDLQo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=gWCwj/zQS5bhbL3vacOcBhGASMWmWNqJs2jpf4iHMmUkPxeuDYWZvAuHxqS1Tr0+gGq+lZDrM6iB06AmaDljOT8xkOIK9CPJsNDC4rg7dss9WrWICnSINzizO2lOD2RA3vJKwkGNLIShrsruIZ/+K9cI2ogVqLFr4EszaxTPthI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=bElAIKkS; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="bElAIKkS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B0C45C433C7; Sun, 25 Feb 2024 10:45:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1708857949; bh=xaEEwq+zhwXXlXUsjzZ1qKHdigMxUKVoFzGsp+eDLQo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=bElAIKkS0nZ5nI2Igh69rC7Xfk/xt7Sv1fU0GpVr6WHie65ArcfLGblmx6+f/eKmd 1pSeTX+oGvXb8s3DWKZG03NiGEHdFFSX/1jgRFPa/78p05yW8jC5DAwAZD1GaVUSXk Y92kQYZ+TjMbOJNcWv1CPzKKjKWU02x1ncaGURW4= Date: Sun, 25 Feb 2024 11:45:43 +0100 From: Greg KH To: Gao Xiang Cc: stable@vger.kernel.org, linux-erofs@lists.ozlabs.org, Juhyung Park , Yifan Zhao Subject: Re: [PATCH 5.10.y] erofs: fix lz4 inplace decompression Message-ID: <2024022527-voicing-overbite-04be@gregkh> References: <2024012650-altitude-gush-572f@gregkh> <20240224063248.2157885-1-hsiangkao@linux.alibaba.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240224063248.2157885-1-hsiangkao@linux.alibaba.com> On Sat, Feb 24, 2024 at 02:32:48PM +0800, Gao Xiang wrote: > commit 3c12466b6b7bf1e56f9b32c366a3d83d87afb4de upstream. > > Currently EROFS can map another compressed buffer for inplace > decompression, that was used to handle the cases that some pages of > compressed data are actually not in-place I/O. > > However, like most simple LZ77 algorithms, LZ4 expects the compressed > data is arranged at the end of the decompressed buffer and it > explicitly uses memmove() to handle overlapping: > __________________________________________________________ > |_ direction of decompression --> ____ |_ compressed data _| > > Although EROFS arranges compressed data like this, it typically maps two > individual virtual buffers so the relative order is uncertain. > Previously, it was hardly observed since LZ4 only uses memmove() for > short overlapped literals and x86/arm64 memmove implementations seem to > completely cover it up and they don't have this issue. Juhyung reported > that EROFS data corruption can be found on a new Intel x86 processor. > After some analysis, it seems that recent x86 processors with the new > FSRM feature expose this issue with "rep movsb". > > Let's strictly use the decompressed buffer for lz4 inplace > decompression for now. Later, as an useful improvement, we could try > to tie up these two buffers together in the correct order. > > Reported-and-tested-by: Juhyung Park > Closes: https://lore.kernel.org/r/CAD14+f2AVKf8Fa2OO1aAUdDNTDsVzzR6ctU_oJSmTyd6zSYR2Q@mail.gmail.com > Fixes: 0ffd71bcc3a0 ("staging: erofs: introduce LZ4 decompression inplace") > Fixes: 598162d05080 ("erofs: support decompress big pcluster for lz4 backend") > Cc: stable # 5.4+ > Tested-by: Yifan Zhao > Signed-off-by: Gao Xiang > Link: https://lore.kernel.org/r/20231206045534.3920847-1-hsiangkao@linux.alibaba.com > --- > Adapt 5.10.y codebase due to non-trivial conflicts out of > recent new features & cleanups. Both now queued up, thanks. greg k-h