Re: [PATCH] parisc: fix inability to allocate stack pages on exec

[Mikulas Patocka <mpatocka@redhat.com>]

On Mon, 3 Jul 2023, Linus Torvalds wrote:

> On Mon, 3 Jul 2023 at 12:59, Mikulas Patocka <mpatocka@redhat.com> wrote:
> >
> > The patch 8d7071af8907 ("mm: always expand the stack with the mmap write
> > lock held") breaks PA-RISC.
> >
> > The breakage happens if we attempt to pass more arguments to execve than
> > what fits into the initial stack page - we get -E2BIG in such a case.
> >
> > The reason for the breakage is that the commit 8d7071af8907 adds the test
> > "if (!(vma->vm_flags & VM_GROWSDOWN)) return -EFAULT;" to the function
> > expand_downwards.
> 
> Heh. See
> 
>    https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f66066bc5136f25e36a2daff4896c768f18c211e
> 
> which fixes this differently (and, I think, much better).
> 
> Just removing the VM_GROWSDOWN test will actually break some of the other users.
> 
> Notably the new and improved expand_stack() function that now handles
> all the complicated *cough*ia64*cough* cases automatically, which
> allowed unifying the page fault handling code around this area.
> 
>               Linus

Yes - I confirm that this fixes it.

(please, also send this patch to Greg, so that it will be included in 
6.4.2)

Mikulas