Re: [PATCH] Fix compat regression in process_vm_rw()

[Naresh Kamboju]

On Wed, 28 Oct 2020 at 00:49, damian
<damian.tometzki@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Mo, 26. Okt 18:03, Jens Axboe wrote:
> > The removal of compat_process_vm_{readv,writev} didn't change
> > process_vm_rw(), which always assumes it's not doing a compat syscall.
> > Instead of passing in 'false' unconditionally for 'compat', make it
> > conditional on in_compat_syscall().
> >
> > Fixes: c3973b401ef2 ("mm: remove compat_process_vm_{readv,writev}")
> > Reported-by: Kyle Huey <me@xxxxxxxxxxxx>
> > Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
> >
> > ---
> >
> > diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
> > index fd12da80b6f2..05676722d9cd 100644
> > --- a/mm/process_vm_access.c
> > +++ b/mm/process_vm_access.c
> > @@ -273,7 +273,8 @@ static ssize_t process_vm_rw(pid_t pid,
> >               return rc;
> >       if (!iov_iter_count(&iter))
> >               goto free_iov_l;
> > -     iov_r = iovec_from_user(rvec, riovcnt, UIO_FASTIOV, iovstack_r, false);
> > +     iov_r = iovec_from_user(rvec, riovcnt, UIO_FASTIOV, iovstack_r,
> > +                             in_compat_syscall());
> >       if (IS_ERR(iov_r)) {
> >               rc = PTR_ERR(iov_r);
> >               goto free_iov_l;
> >
> > --
> > Jens Axboe
> >
> Hello Jens,
>
> i got the following error when i try to build.
>
> m/process_vm_access.c: In Funktion »process_vm_rw«:
> mm/process_vm_access.c:277:5: Fehler: Implizite Deklaration der Funktion »in_compat_syscall«; meinten Sie »in_ia32_syscall«? [-Werror=implicit-function-declaration]
>   277 |     in_compat_syscall());
>       |     ^~~~~~~~~~~~~~~~~
>       |     in_ia32_syscall
>

I have also noticed this build failure on Linus's mainline master branch.

x86_64 : FAILED
i386: FAILED
arm: FAILED

make -sk KBUILD_BUILD_USER=TuxBuild -C/linux -j16 ARCH=x86 HOSTCC=gcc
CC="sccache gcc" O=build

50../mm/process_vm_access.c: In function ‘process_vm_rw’:
51../mm/process_vm_access.c:277:5: error: implicit declaration of
function ‘in_compat_syscall’; did you mean ‘in_ia32_syscall’?
[-Werror=implicit-function-declaration]
52 277 | in_compat_syscall());
53 | ^~~~~~~~~~~~~~~~~
54 | in_ia32_syscall
55cc1: some warnings being treated as errors


Reported-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>

full test build log:
https://gitlab.com/Linaro/lkft/mirrors/torvalds/linux-mainline/-/jobs/815202967


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