linux-kernel - Re: [PATCH 6.6 00/28] fix CVE-2024-46701

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Message-ID: <epkfxxakvk5bsiucbfvrdgjcndpzumabljuginymvviv5edpxg@czr5gtkzxjyb>
Date: Thu, 7 Nov 2024 09:44:24 -0500
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Yu Kuai <yukuai1@...weicloud.com>
Cc: Chuck Lever III <chuck.lever@...cle.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        linux-stable <stable@...r.kernel.org>,
        "harry.wentland@....com" <harry.wentland@....com>,
        "sunpeng.li@....com" <sunpeng.li@....com>,
        "Rodrigo.Siqueira@....com" <Rodrigo.Siqueira@....com>,
        "alexander.deucher@....com" <alexander.deucher@....com>,
        "christian.koenig@....com" <christian.koenig@....com>,
        "Xinhui.Pan@....com" <Xinhui.Pan@....com>,
        "airlied@...il.com" <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, Al Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Sasha Levin <sashal@...nel.org>,
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        yangerkun <yangerkun@...wei.com>, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH 6.6 00/28] fix CVE-2024-46701

* Yu Kuai <yukuai1@...weicloud.com> [241106 19:57]:
> Hi,
> 
> 在 2024/11/06 23:19, Chuck Lever III 写道:
> > 
> > 
> > > On Nov 6, 2024, at 1:16 AM, Greg KH <gregkh@...uxfoundation.org> wrote:
> > > 
> > > On Thu, Oct 24, 2024 at 09:19:41PM +0800, Yu Kuai wrote:
> > > > From: Yu Kuai <yukuai3@...wei.com>
> > > > 
> > > > Fix patch is patch 27, relied patches are from:
> > 
> > I assume patch 27 is:
> > 
> > libfs: fix infinite directory reads for offset dir
> > 
> > https://lore.kernel.org/stable/20241024132225.2271667-12-yukuai1@huaweicloud.com/
> > 
> > I don't think the Maple tree patches are a hard
> > requirement for this fix. And note that libfs did
> > not use Maple tree originally because I was told
> > at that time that Maple tree was not yet mature.
> > 
> > So, a better approach might be to fit the fix
> > onto linux-6.6.y while sticking with xarray.
> 
> The painful part is that using xarray is not acceptable, the offet
> is just 32 bit and if it overflows, readdir will read nothing. That's
> why maple_tree has to be used.

Why does the xarray cause it to overflow vs the maple tree? The maple
tree conversion was for performance reasons, as far as I know [1].

Thanks,
Liam

[1]. https://lore.kernel.org/all/170820083431.6328.16233178852085891453.stgit@91.116.238.104.host.secureserver.net/

> 
> Thanks,
> Kuai
> 
> > 
> > This is the first I've heard of this CVE. It
> > would help if the patch authors got some
> > notification when these are filed.
> > 
> > 
> > > > - patches from set [1] to add helpers to maple_tree, the last patch to
> > > > improve fork() performance is not backported;
> > > 
> > > So things slowed down?
> > > 
> > > > - patches from set [2] to change maple_tree, and follow up fixes;
> > > > - patches from set [3] to convert offset_ctx from xarray to maple_tree;
> > > > 
> > > > Please notice that I'm not an expert in this area, and I'm afraid to
> > > > make manual changes. That's why patch 16 revert the commit that is
> > > > different from mainline and will cause conflict backporting new patches.
> > > > patch 28 pick the original mainline patch again.
> > > > 
> > > > (And this is what we did to fix the CVE in downstream kernels).
> > > > 
> > > > [1] https://lore.kernel.org/all/20231027033845.90608-1-zhangpeng.00@bytedance.com/
> > > > [2] https://lore.kernel.org/all/20231101171629.3612299-2-Liam.Howlett@oracle.com/T/
> > > > [3] https://lore.kernel.org/all/170820083431.6328.16233178852085891453.stgit@91.116.238.104.host.secureserver.net/
> > > 
> > > This series looks rough.  I want to have the maintainers of these
> > > files/subsystems to ack this before being able to take them.
> > > 
> > > thanks,
> > > 
> > > greg k-h
> > 
> > --
> > Chuck Lever
> > 
> > 
>