Re: [PATCH for-stable] LoongArch: Define __ARCH_WANT_NEW_STAT in unistd.h

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Wed, Jul 31, 2024 at 09:06:56AM +0800, Huacai Chen wrote:
> On Tue, Jul 30, 2024 at 10:24 PM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> >
> > On Tue, Jul 30, 2024 at 10:25:42AM +0800, Huacai Chen wrote:
> > > Chromium sandbox apparently wants to deny statx [1] so it could properly
> > > inspect arguments after the sandboxed process later falls back to fstat.
> > > Because there's currently not a "fd-only" version of statx, so that the
> > > sandbox has no way to ensure the path argument is empty without being
> > > able to peek into the sandboxed process's memory. For architectures able
> > > to do newfstatat though, glibc falls back to newfstatat after getting
> > > -ENOSYS for statx, then the respective SIGSYS handler [2] takes care of
> > > inspecting the path argument, transforming allowed newfstatat's into
> > > fstat instead which is allowed and has the same type of return value.
> > >
> > > But, as LoongArch is the first architecture to not have fstat nor
> > > newfstatat, the LoongArch glibc does not attempt falling back at all
> > > when it gets -ENOSYS for statx -- and you see the problem there!
> > >
> > > Actually, back when the LoongArch port was under review, people were
> > > aware of the same problem with sandboxing clone3 [3], so clone was
> > > eventually kept. Unfortunately it seemed at that time no one had noticed
> > > statx, so besides restoring fstat/newfstatat to LoongArch uapi (and
> > > postponing the problem further), it seems inevitable that we would need
> > > to tackle seccomp deep argument inspection.
> > >
> > > However, this is obviously a decision that shouldn't be taken lightly,
> > > so we just restore fstat/newfstatat by defining __ARCH_WANT_NEW_STAT
> > > in unistd.h. This is the simplest solution for now, and so we hope the
> > > community will tackle the long-standing problem of seccomp deep argument
> > > inspection in the future [4][5].
> > >
> > > More infomation please reading this thread [6].
> > >
> > > [1] https://chromium-review.googlesource.com/c/chromium/src/+/2823150
> > > [2] https://chromium.googlesource.com/chromium/src/sandbox/+/c085b51940bd/linux/seccomp-bpf-helpers/sigsys_handlers.cc#355
> > > [3] https://lore.kernel.org/linux-arch/20220511211231.GG7074@brightrain.aerifal.cx/
> > > [4] https://lwn.net/Articles/799557/
> > > [5] https://lpc.events/event/4/contributions/560/attachments/397/640/deep-arg-inspection.pdf
> > > [6] https://lore.kernel.org/loongarch/20240226-granit-seilschaft-eccc2433014d@brauner/T/#t
> > >
> > > Cc: stable@vger.kernel.org
> > > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> > > ---
> > >  arch/loongarch/include/uapi/asm/unistd.h | 1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > diff --git a/arch/loongarch/include/uapi/asm/unistd.h b/arch/loongarch/include/uapi/asm/unistd.h
> > > index fcb668984f03..b344b1f91715 100644
> > > --- a/arch/loongarch/include/uapi/asm/unistd.h
> > > +++ b/arch/loongarch/include/uapi/asm/unistd.h
> > > @@ -1,4 +1,5 @@
> > >  /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> > > +#define __ARCH_WANT_NEW_STAT
> > >  #define __ARCH_WANT_SYS_CLONE
> > >  #define __ARCH_WANT_SYS_CLONE3
> > >
> > > --
> > > 2.43.5
> > >
> > >
> >
> > What kernel branch(s) is this for?
> For 6.1~6.10.

What is the git id of this change in Linus's tree?