Re: Userspace regression in LTS and stable kernels

From: Andrew Morton
Date: Thu Feb 14 2019 - 15:20:34 EST

On Thu, 14 Feb 2019 09:56:46 -0800 Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> On Wed, Feb 13, 2019 at 3:37 PM Richard Weinberger
> <richard.weinberger@xxxxxxxxx> 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.

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.