linux-kernel - Re: [PATCH 3/3] erofs: handle corrupted images whose decompressed size less than it'd be

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Date:   Wed, 26 Feb 2020 10:44:08 +0800
From:   Gao Xiang <gaoxiang25@...wei.com>
To:     Eric Biggers <ebiggers@...nel.org>
CC:     Chao Yu <yuchao0@...wei.com>, <linux-erofs@...ts.ozlabs.org>,
        Miao Xie <miaoxie@...wei.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Lasse Collin <lasse.collin@...aani.org>
Subject: Re: [PATCH 3/3] erofs: handle corrupted images whose decompressed
 size less than it'd be

On Wed, Feb 26, 2020 at 10:40:47AM +0800, Gao Xiang wrote:
> Hi Eric,
> 
> On Tue, Feb 25, 2020 at 06:34:58PM -0800, Eric Biggers wrote:
> > On Wed, Feb 26, 2020 at 10:30:11AM +0800, Gao Xiang wrote:
> > > As Lasse pointed out, "Looking at fs/erofs/decompress.c,
> > > the return value from LZ4_decompress_safe_partial is only
> > > checked for negative value to catch errors. ... So if
> > > I understood it correctly, if there is bad data whose
> > > uncompressed size is much less than it should be, it can
> > > leave part of the output buffer untouched and expose the
> > > previous data as the file content. "
> > > 
> > > Let's fix it now.
> > > 
> > > Cc: Lasse Collin <lasse.collin@...aani.org>
> > > Signed-off-by: Gao Xiang <gaoxiang25@...wei.com>
> > 
> > Shouldn't fixes like this have a Fixes tag and Cc stable?
> > 
> > - Eric
> 
> Thanks for pointing out. *thumb up*
> 
> I reminded Fixes and Cc tags when I sent out. Yet
> I'm not quite sure if these have some other potential
> concernes which could cause unexpected behavior for
> normal images (It seems impossible but not quite sure.)
> 
> I'd like to leave these two commits for corrupted images
> to mainline and our products for a while and manually
> backport to stable kernels and send them to stable
> mailing list later. I keep these fixes in mind all
> the time.

... Maybe I should add "Fixes:" tag in the commit message
anyway. Will resend them later.

Thanks,
Gao Xiang

> 
> Thanks,
> Gao Xiang
>