From: Martin Schwidefsky <schwidefsky@de•ibm.com>
To: Steven Rostedt <rostedt@goodmis•org>
Cc: Petr Mladek <pmladek@suse•com>,
linux-arch@vger•kernel.org,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail•com>,
Heiko Carstens <heiko.carstens@de•ibm.com>,
linux-s390@vger•kernel.org, linuxppc-dev@lists•ozlabs.org,
Rasmus Villemoes <linux@rasmusvillemoes•dk>,
linux-kernel@vger•kernel.org, Michal Hocko <mhocko@suse•cz>,
Sergey Senozhatsky <sergey.senozhatsky@gmail•com>,
Stephen Rothwell <sfr@ozlabs•org>,
Andy Shevchenko <andriy.shevchenko@linux•intel.com>,
Linus Torvalds <torvalds@linux-foundation•org>,
"Tobin C . Harding" <me@tobin•cc>
Subject: Re: [PATCH] vsprintf: Do not break early boot with probing addresses
Date: Fri, 10 May 2019 18:45:48 +0200 [thread overview]
Message-ID: <20190510184548.1eda01a9@mschwideX1> (raw)
In-Reply-To: <20190510124058.0d44b441@gandalf.local.home>
On Fri, 10 May 2019 12:40:58 -0400
Steven Rostedt <rostedt@goodmis•org> wrote:
> On Fri, 10 May 2019 18:32:58 +0200
> Martin Schwidefsky <schwidefsky@de•ibm.com> wrote:
>
> > On Fri, 10 May 2019 12:24:01 -0400
> > Steven Rostedt <rostedt@goodmis•org> wrote:
> >
> > > On Fri, 10 May 2019 10:42:13 +0200
> > > Petr Mladek <pmladek@suse•com> wrote:
> > >
> > > > static const char *check_pointer_msg(const void *ptr)
> > > > {
> > > > - char byte;
> > > > -
> > > > if (!ptr)
> > > > return "(null)";
> > > >
> > > > - if (probe_kernel_address(ptr, byte))
> > > > + if ((unsigned long)ptr < PAGE_SIZE || IS_ERR_VALUE(ptr))
> > > > return "(efault)";
> > > >
> > >
> > >
> > > < PAGE_SIZE ?
> > >
> > > do you mean: < TASK_SIZE ?
> >
> > The check with < TASK_SIZE would break on s390. The 'ptr' is
> > in the kernel address space, *not* in the user address space.
> > Remember s390 has two separate address spaces for kernel/user
> > the check < TASK_SIZE only makes sense with a __user pointer.
> >
>
> So we allow this to read user addresses? Can't that cause a fault?
>
> If the condition is true, we return "(efault)".
On x86 this would allow a user space access as kernel and user live
in the same address space, on s390 it would not.
h
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
next prev parent reply other threads:[~2019-05-10 16:47 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-09 12:19 [PATCH] vsprintf: Do not break early boot with probing addresses Petr Mladek
2019-05-09 13:05 ` Andy Shevchenko
2019-05-09 13:13 ` Steven Rostedt
2019-05-09 14:06 ` Petr Mladek
2019-05-09 13:38 ` Michal Suchánek
2019-05-09 13:46 ` David Laight
2019-05-10 10:21 ` Michael Ellerman
2019-05-10 4:32 ` Sergey Senozhatsky
2019-05-10 4:47 ` Linus Torvalds
2019-05-10 5:07 ` Sergey Senozhatsky
2019-05-10 6:41 ` Michael Ellerman
2019-05-10 8:06 ` Petr Mladek
2019-05-10 8:16 ` Sergey Senozhatsky
2019-05-10 8:42 ` Petr Mladek
2019-05-10 8:51 ` Sergey Senozhatsky
2019-05-10 14:49 ` Petr Mladek
2019-05-10 16:24 ` Steven Rostedt
2019-05-10 16:32 ` Martin Schwidefsky
2019-05-10 16:40 ` Steven Rostedt
2019-05-10 16:45 ` Martin Schwidefsky [this message]
2019-05-13 12:24 ` Petr Mladek
2019-05-10 16:41 ` Andy Shevchenko
2019-05-10 17:35 ` christophe leroy
2019-05-13 8:52 ` David Laight
2019-05-13 9:13 ` Andy Shevchenko
2019-05-13 12:42 ` Petr Mladek
2019-05-13 14:15 ` Steven Rostedt
2019-05-14 2:07 ` Sergey Senozhatsky
2019-05-14 2:25 ` Sergey Senozhatsky
2019-05-14 8:28 ` David Laight
2019-05-14 9:02 ` Geert Uytterhoeven
2019-05-14 18:37 ` Steven Rostedt
2019-05-14 19:13 ` Geert Uytterhoeven
2019-05-14 19:35 ` Steven Rostedt
2019-05-15 7:23 ` Geert Uytterhoeven
2019-05-15 7:53 ` Petr Mladek
2019-05-15 6:21 ` Sergey Senozhatsky
2019-05-15 7:35 ` Petr Mladek
2019-05-15 9:00 ` David Laight
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