linux-kernel - Re: [PATCH v2] MIPS: kernel: Fix random segmentation faults

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Message-ID: <CAAhV-H6oncTWGXRO_n3B-JR_qnro-=4jg5-qwRnpTox5qr=CXQ@mail.gmail.com>
Date: Thu, 20 Nov 2025 20:32:08 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>, Thomas Gleixner <tglx@...utronix.de>, 
	Nam Cao <namcao@...utronix.de>, linux-mips@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] MIPS: kernel: Fix random segmentation faults

On Thu, Nov 20, 2025 at 8:21 PM Thomas Weißschuh
<thomas.weissschuh@...utronix.de> wrote:
>
> On Thu, Nov 20, 2025 at 01:10:29PM +0100, Thomas Bogendoerfer wrote:
> > Commit 69896119dc9d ("MIPS: vdso: Switch to generic storage
> > implementation") switches to a generic vdso storage, which increases
> > the number of data pages from 1 to 4. But there is only one page
> > reserved, which causes segementation faults depending where the VDSO
> > area is randomized to. To fix this use the same size of reservation
> > and allocation of the VDSO data pages.
> >
> > Fixes: 69896119dc9d ("MIPS: vdso: Switch to generic storage implementation")
>
> Thanks!
>
> Reviewed-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Reviewed-by: Huacai Chen <chenhuacai@...ngson.cn>

>
> > Signed-off-by: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
> > ---
> > v2: Don't reserve additionnal VDSO_NR_PAGES, but reserve VDSO_NR_PAGES
> >     instead of the one page before.
> >     Reworked description
> > v1: https://lore.kernel.org/all/20251117191815.69556-1-tsbogend@alpha.franken.de/
> >
> >  arch/mips/kernel/process.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
> > index 29191fa1801e..a3101f2268c6 100644
> > --- a/arch/mips/kernel/process.c
> > +++ b/arch/mips/kernel/process.c
> > @@ -692,7 +692,7 @@ unsigned long mips_stack_top(void)
> >       /* Space for the VDSO, data page & GIC user page */
> >       if (current->thread.abi) {
> >               top -= PAGE_ALIGN(current->thread.abi->vdso->size);
> > -             top -= PAGE_SIZE;
> > +             top -= VDSO_NR_PAGES * PAGE_SIZE;
> >               top -= mips_gic_present() ? PAGE_SIZE : 0;
> >
> >               /* Space to randomize the VDSO base */
> > --
> > 2.43.0
> >
>