[PATCH 11/15] mips: fix n32 compat_ipc_parse_version

[Arnd Bergmann]

On Thu, Jan 10, 2019 at 8:40 PM Paul Burton <paul.burton at mips.com> wrote:
> On Thu, Jan 10, 2019 at 05:24:31PM +0100, Arnd Bergmann wrote:
> > While reading through the sysvipc implementation, I noticed that the n32
> > semctl/shmctl/msgctl system calls behave differently based on whether
> > o32 support is enabled or not: Without o32, the IPC_64 flag passed by
> > user space is rejected but calls without that flag get IPC_64 behavior.
> >
> > As far as I can tell, this was inadvertently changed by a cleanup patch
> > but never noticed by anyone, possibly nobody has tried using sysvipc
> > on n32 after linux-3.19.
> >
> > Change it back to the old behavior now.
> >
> > Fixes: 78aaf956ba3a ("MIPS: Compat: Fix build error if CONFIG_MIPS32_COMPAT but no compat ABI.")
> > Cc: stable at vger.kernel.org
> > Signed-off-by: Arnd Bergmann <arnd at arndb.de>
> > ---
> > As stated above, this was only found by inspection, the patch is not
> > tested. Please review accordingly.
>
> Nice catch! Would you prefer to merge this yourself, or that I take it
> through the mips tree?

Up to you: if you want to merge it for 5.0, I'll just drop it from my tree.

> If the former then:
>
>   Acked-by: Paul Burton <paul.burton at mips.com>

Thanks!

> I suspect kernels configured with n32 support but no o32 support are
> probably not very common - for internal testing we currently always
> enable both.

Do you know of anyone actually still using n32 in production systems
with 4.x kernels? I wonder if it just fell out of popularity as the 64-bit
machines that used it either became large enough to want 64-bit
user space, or got replaced by arm64 or mips32 hardware.

      Arnd