Hi Zi,
On Wed, Dec 4, 2024 at 4:24 PM Zi Yan <ziy@xxxxxxxxxx> wrote:
> On 4 Dec 2024, at 5:41, Geert Uytterhoeven wrote:
> > On Fri, Oct 11, 2024 at 5:13 PM Zi Yan <ziy@xxxxxxxxxx> wrote:
> >> Commit 6471384af2a6 ("mm: security: introduce init_on_alloc=1 and
> >> init_on_free=1 boot options") forces allocated page to be zeroed in
> >> post_alloc_hook() when init_on_alloc=1.
> >>
> >> For order-0 folios, if arch does not define
> >> vma_alloc_zeroed_movable_folio(), the default implementation again zeros
> >> the page return from the buddy allocator. So the page is zeroed twice.
> >> Fix it by passing __GFP_ZERO instead to avoid double page zeroing.
> >> At the moment, s390,arm64,x86,alpha,m68k are not impacted since they
> >> define their own vma_alloc_zeroed_movable_folio().
> >>
> >> For >0 order folios (mTHP and PMD THP), folio_zero_user() is called to
> >> zero the folio again. Fix it by calling folio_zero_user() only if
> >> init_on_alloc is set. All arch are impacted.
> >>
> >> Added alloc_zeroed() helper to encapsulate the init_on_alloc check.
> >>
> >> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
> >
> > Thanks for your patch, which is now commit 5708d96da20b99b4 ("mm:
> > avoid zeroing user movable page twice with init_on_alloc=1")
> > in v6.13-rc1.
> >
> > This causing a panic when starting userspace on MIPS64 RBTX4927:
> >
> > Run /sbin/init as init process
> > process '/lib/systemd/systemd' started with executable stack
> > Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
> > ---[ end Kernel panic - not syncing: Attempted to kill init!
> > exitcode=0x0000000b ]---
> >
> > or
> >
> > Run /sbin/init as init process
> > process '/lib/systemd/systemd' started with executable stack
> > do_page_fault(): sending SIGSEGV to init for invalid read access
> > from 00000000583399f8
> > epc = 0000000077e2b094 in ld-2.19.so[3094,77e28000+22000]
> > ra = 0000000077e2afcc in ld-2.19.so[2fcc,77e28000+22000]
> > Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
> > ---[ end Kernel panic - not syncing: Attempted to kill init!
> > exitcode=0x0000000b ]---
> >
> > or
> >
> > Run /sbin/init as init process
> > process '/lib/systemd/systemd' started with executable stack
> > /sbin/inKernel panic - not syncing: Attempted to kill init!
> > exitcode=0x00007f00
> > ---[ end Kernel panic - not syncing: Attempted to kill init!
> > exitcode=0x00007f00 ]---
> > it: error while loading shared libraries: libpthread.so.0: object
> > file has no dynamic section
> >
> > Reverting the commit (and fixing the trivial conflict) fixes the issue.
> The provided config does not have THP on, so the changes to mm/huge_memory.c
> and mm/memory.c do not apply.
>
> Can you try the patch below and see if the machine boots? Thanks.
> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
> index 6e452bd8e7e3..bec9bd715acf 100644
> --- a/include/linux/highmem.h
> +++ b/include/linux/highmem.h
> @@ -224,7 +224,13 @@ static inline
> struct folio *vma_alloc_zeroed_movable_folio(struct vm_area_struct *vma,
> unsigned long vaddr)
> {
> - return vma_alloc_folio(GFP_HIGHUSER_MOVABLE | __GFP_ZERO, 0, vma, vaddr);
> + struct folio *folio;
> +
> + folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, vaddr);
> + if (folio)
> + clear_user_highpage(&folio->page, vaddr);
> +
> + return folio;
> }
> #endif
Thanks, that works!
Tested-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
