linux-kernel - Re: Userspace regression in LTS and stable kernels

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Message-ID: <20190215071303.GA29700@kroah.com>
Date:   Fri, 15 Feb 2019 08:13:03 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     stable@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Richard Weinberger <richard.weinberger@...il.com>,
        Samuel Dionne-Riel <samuel@...nne-riel.com>,
        LKML <linux-kernel@...r.kernel.org>, graham@...hamc.com,
        Oleg Nesterov <oleg@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: Userspace regression in LTS and stable kernels

On Fri, Feb 15, 2019 at 08:00:22AM +0100, Greg Kroah-Hartman wrote:
> On Thu, Feb 14, 2019 at 12:20:27PM -0800, Andrew Morton wrote:
> > On Thu, 14 Feb 2019 09:56:46 -0800 Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> > 
> > > On Wed, Feb 13, 2019 at 3:37 PM Richard Weinberger
> > > <richard.weinberger@...il.com> wrote:
> > > >
> > > > Your shebang line exceeds BINPRM_BUF_SIZE.
> > > > Before the said commit the kernel silently truncated the shebang line
> > > > (and corrupted it),
> > > > now it tells the user that the line is too long.
> > > 
> > > It doesn't matter if it "corrupted" things by truncating it. All that
> > > matters is "it used to work, now it doesn't"
> > > 
> > > Yes, maybe it never *should* have worked. And yes, it's sad that
> > > people apparently had cases that depended on this odd behavior, but
> > > there we are.
> > > 
> > > I see that Kees has a patch to fix it up.
> > > 
> > 
> > Greg, I think we have a problem here.
> > 
> > 8099b047ecc431518 ("exec: load_script: don't blindly truncate shebang
> > string") wasn't marked for backporting.  And, presumably as a
> > consequence, Kees's fix "exec: load_script: allow interpreter argument
> > truncation" was not marked for backporting.
> > 
> > 8099b047ecc431518 hasn't even appeared in a Linus released kernel, yet
> > it is now present in 4.9.x, 4.14.x, 4.19.x and 4.20.x.
> 
> It came in 5.0-rc1, so it fits the "in a Linus released kernel"
> requirement.  If we are to wait until it shows up in a -final, that
> would be months too late for almost all of these types of patches that
> are picked up.
> 
> > I don't know if Oleg considered backporting that patch.  I certainly
> > did (I always do), and I decided against doing so.  Yet there it is.
> 
> This came in through Sasha's tools, which give people a week or so to
> say "hey, this isn't a stable patch!" and it seems everyone ignored that
> :(
> 
> Where is Kees's fix?  I'll be glad to queue it up, or just revert the
> above commit, which ever people think is easiest.

Ah, I see the fix now, _after_ I just pushed out a bunch of stable
releases.  I'll go queue it up and push it out with just that fix in it
now...

thanks,

greg k-h