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

2020-10-27 Thread Jens Axboe 
On 10/27/20 1:19 PM, damian 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 
>> Signed-off-by: Jens Axboe 
>>
>> ---
>>
>> 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())
>>  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

Yeah, sorry about that. Geert sent out a fix:

https://lore.kernel.org/lkml/20201027182246.651908-1-geert+rene...@glider.be/

-- 
Jens Axboe

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

2020-10-27 Thread Naresh Kamboju 
On Wed, 28 Oct 2020 at 00:49, damian
 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 
> > Signed-off-by: Jens Axboe 
> >
> > ---
> >
> > 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())
> >   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 

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


-- 
Linaro LKFT
https://lkft.linaro.org

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

2020-10-27 Thread damian 
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 
> Signed-off-by: Jens Axboe 
> 
> ---
> 
> 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())
>   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

-- 
VG
Damian Tometzki

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

2020-10-27 Thread Linus Torvalds 
On Tue, Oct 27, 2020 at 1:01 AM Christoph Hellwig  wrote:
>
> Independent of this fix I think we just need to explicitly prohibit
> cross-access.

Well, prohibiting a 32-bit process from accessing a 64-bit one might
make sense, since it fundamentally cannot work, and returning an
explicit error early might help avoid confusion.

But a 64-bit one can certainly validly look at a 32-bit one (ie
debugging a compat process from a 64-bit gdb or similar is not
unreasonable).

That said, I wonder how muich of a problem that can be, so it may be
sufficient to just fix this compat case up and leave it alone.

So applied,

Linus

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

2020-10-27 Thread Christoph Hellwig 
On Tue, Oct 27, 2020 at 12:09:20AM +, Al Viro wrote:
> On Mon, Oct 26, 2020 at 06:03:18PM -0600, 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 
> > Signed-off-by: Jens Axboe 
> 
> ACK with some reservations - I suspect that we want an explicit flag
> for process_vm_{read,write}v() that would force the 64bit layout for
> the vector refering to the foreign process.  It's not relevant for
> regression fix; however, as it is these syscalls are not usable for
> 32bit process trying to access memory of 64bit one - there's no way
> to specify the addresses past 4G.

Independent of this fix I think we just need to explicitly prohibit
cross-access.

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

2020-10-27 Thread Christoph Hellwig 
Looks good,

Reviewed-by: Christoph Hellwig

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

2020-10-26 Thread Kyle Huey 
On Mon, Oct 26, 2020 at 5:03 PM 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 
> Signed-off-by: Jens Axboe 
>
> ---
>
> 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())
> 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
>

I tested this patch and it does fix the original testcase I reported.

- Kyle

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

2020-10-26 Thread Al Viro 
On Mon, Oct 26, 2020 at 06:03:18PM -0600, 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 
> Signed-off-by: Jens Axboe 

ACK with some reservations - I suspect that we want an explicit flag
for process_vm_{read,write}v() that would force the 64bit layout for
the vector refering to the foreign process.  It's not relevant for
regression fix; however, as it is these syscalls are not usable for
32bit process trying to access memory of 64bit one - there's no way
to specify the addresses past 4G.

[PATCH] Fix compat regression in process_vm_rw()

2020-10-26 Thread Jens Axboe 
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 
Signed-off-by: Jens Axboe 

---

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())
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