Re: Chromium sandbox on LoongArch and statx -- seccomp deep argument inspection again?

[Christian Brauner]

On Mon, Feb 26, 2024 at 07:57:56PM +0800, Xi Ruoyao wrote:
> On Mon, 2024-02-26 at 10:20 +0100, Arnd Bergmann wrote:
> 
> /* snip */
> 
> > 
> > > Or maybe we can just introduce a new AT_something to make statx
> > > completely ignore pathname but behave like AT_EMPTY_PATH + "".

I'm not at all convinced about doing custom semantics for this.

> > I think this is better than going back to fstat64_time64(), but
> > it's still not great because
> > 
> > - all the reserved flags on statx() are by definition incompatible
> >   with existing kernels that return -EINVAL for any flag they do
> >   not recognize.
> 
> Oops, we are deeming passing undefined flags in "mask" undefined
> behavior but not "flags", thus "wild software" may be relying on EINVAL
> for invalid flags...  We *might* make this new AT_xxx a bit in mask
> instead of flags but it would be very dirty IMO.

Uhm, no. AT_* flags have nothing to do in statx()'s mask argument at all.