On Wed, Dec 4, 2024 at 1:50 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. > > Thank you for reporting the error. > > > This causing a panic when starting userspace on MIPS64 RBTX4927: > Do you mind providing the full kernel log for this panic? And your kernel > config as well. I am trying to figure out why changing page zeroing from > twice to once can cause kernel panic. Both sent by PM. 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