linux-kernel - Re: [PATCH v3] lz4: fix LZ4_decompress_safe

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Date:   Tue, 5 Apr 2022 06:28:17 +0800
From:   Gao Xiang <hsiangkao@...ux.alibaba.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Nick Terrell <terrelln@...com>, Guo Xuenan <guoxuenan@...wei.com>,
        Chengyang Fan <cy.fan@...wei.com>, Yann Collet <cyan@...com>,
        "fangwei1@...wei.com" <fangwei1@...wei.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "syzbot+63d688f1d899c588fb71@...kaller.appspotmail.com" 
        <syzbot+63d688f1d899c588fb71@...kaller.appspotmail.com>,
        "wangli74@...wei.com" <wangli74@...wei.com>
Subject: Re: [PATCH v3] lz4: fix LZ4_decompress_safe_partial read out of bound

On Mon, Apr 04, 2022 at 02:21:23PM -0700, Andrew Morton wrote:
> On Sat, 2 Apr 2022 12:55:39 +0800 Gao Xiang <hsiangkao@...ux.alibaba.com> wrote:
> 
> > On Fri, Nov 19, 2021 at 06:23:24PM +0000, Nick Terrell wrote:
> > > 
> > > 
> > > > On Nov 11, 2021, at 2:50 AM, Guo Xuenan <guoxuenan@...wei.com> wrote:
> > > > 
> > > > When partialDecoding, it is EOF if we've either, filled the output
> > > > buffer or can't proceed with reading an offset for following match.
> > > > 
> > > > In some extreme corner cases when compressed data is crusted corrupted,
> > > > UAF will occur. As reported by KASAN [1], LZ4_decompress_safe_partial
> > > > may lead to read out of bound problem during decoding. lz4 upstream has
> > > > fixed it [2] and this issue has been disscussed here [3] before.
> > > > 
> > > > current decompression routine was ported from lz4 v1.8.3, bumping lib/lz4
> > > > to v1.9.+ is certainly a huge work to be done later, so, we'd better fix
> > > > it first.
> > > > 
> > > > [1] https://lore.kernel.org/all/000000000000830d1205cf7f0477@google.com/
> > > > [2] https://github.com/lz4/lz4/commit/c5d6f8a8be3927c0bec91bcc58667a6cfad244ad#
> > > > [3] https://lore.kernel.org/all/CC666AE8-4CA4-4951-B6FB-A2EFDE3AC03B@fb.com/
> > > > 
> > > > Reported-by: syzbot+63d688f1d899c588fb71@...kaller.appspotmail.com
> > > > Cc: hsiangkao@...ux.alibaba.com
> > > > Cc: terrelln@...com
> > > > Cc: cyan@...com
> > > > Cc: cy.fan@...wei.com
> > > > Signed-off-by: Guo Xuenan <guoxuenan@...wei.com>
> > > 
> > > Sorry I’m a bit late to the party, but this looks good to me!
> > > 
> > > Reviewed-by: Nick Terrell <terrelln@...com>
> > 
> > Acked-by: Gao Xiang <hsiangkao@...ux.alibaba.com>
> > 
> > Hi Andrew,
> > 
> > This patch has already been pending for 2 release cycles.. Would you
> > mind submitting it upstream? Or are there other concerns about this?
> 
> Sorry, I'd not noticed that this was from lz4 upstream.
> 
> I'll put a cc:stable in there and shall send it upstream this week.
> 
> In the changelog, can someone please explain what "crusted corrupted"
> is saying?

Er.. It sounds like "well-designed corrupted". I think it was a typo
though.

Thanks,
Gao Xiang