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SubjectRe: [PATCH] fs/binfmt_elf: use ELF_ET_DYN_BASE for PIE (ET_DYN with INTERP) binaries
On Tue, Feb 01, 2022 at 05:39:57AM -0800, H.J. Lu wrote:
> On Tue, Feb 1, 2022 at 5:28 AM Azat Khuzhin <a3at.mail@gmail.com> wrote:
> >
> > On Tue, Feb 01, 2022 at 05:15:38AM -0800, H.J. Lu wrote:
> > > On Mon, Jan 31, 2022 at 10:18 PM Azat Khuzhin <a3at.mail@gmail.com> wrote:
> > > >
> > > > On Mon, Jan 31, 2022 at 01:30:38PM -0800, H.J. Lu wrote:
> > > > > On Mon, Jan 31, 2022 at 12:17 PM Azat Khuzhin <a3at.mail@gmail.com> wrote:
> > > > > >
> > > > > > Since 9630f0d60fec ELF_ET_DYN_BASE is not used as a load_bias anymore
> > > > > > and this breaks PIE binaries, since after this change data segment
> > > > > > became too nearby the stack:
> > > > > >
> > > > > > Before 9630f0d60fec:
> > > > > >
> > > > > > $ strace -febrk /tmp/test-stack |& head
> > > > > > brk(NULL) = 0x555555559000
> > > > > > $ /tmp/test-stack
> > > > > > bottom_of_stack = 0x7fffffffc5c0
> > > > > > recursion depth: 1 (stack diff: 32)
> > > > > > ...
> > > > > > recursion depth: 7690 (stack diff: 8365664)
> > > > > > Segmentation fault (core dumped)
> > > > > >
> > > > > > After 9630f0d60fec:
> > > > > >
> > > > > > $ strace -ebrk /tmp/test-stack |& head
> > > > > > brk(NULL) = 0x7ffff7fff000
> > > > > >
> > > > > > $ /tmp/test-stack
> > > > > > bottom_of_stack = 0x7fffffffc640
> > > > > > recursion depth: 1 (stack diff: 32)
> > > > > > ...
> > > > > > recursion depth: 146 (stack diff: 157792)
> > > > > > Segmentation fault (core dumped)
> > > > > >
> > > > > > Found this during compiling with clang, that started to randomly
> > > > > > SIGSEGV when it eats some heap.
> > > > >
> > > > > How do I reproduce it on x86-64?
> > > >
> > > > It fails for me for pretty big C++ unit, so I don't have a simple
> > > > reproducer with clang, but the attached reproducer below should show the
> > > > problem.
> > >
> > > The reproducer doesn't fail for me under 5.17-rc2 on Fedora 35/x86-64
> > > with 32GB RAM. Did you turn off PF_RANDOMIZE?
> >
> > Oh, yep, forgot to mention that I have kernel.randomize_va_space=0.
>
> PIE with interpreter and PIE with alignment > ELF_MIN_ALIGN
> should always be loaded from ELF_ET_DYN_BASE. Otherwise,
> either PIE is loaded at an address which is too low or isn't properly
> aligned.

So, this is what this patch does, right?
Any news on this patch?

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