LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: "Michal Suchánek" <msuchanek@suse.de>
To: Petr Mladek <pmladek@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	linux-arch@vger.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	linux-s390@vger.kernel.org,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	linux-kernel@vger.kernel.org,
	Steven Rostedt <rostedt@goodmis.org>,
	Michal Hocko <mhocko@suse.cz>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Stephen Rothwell <sfr@ozlabs.org>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	linuxppc-dev@lists.ozlabs.org,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	"Tobin C . Harding" <me@tobin.cc>
Subject: Re: [PATCH] vsprintf: Do not break early boot with probing addresses
Date: Thu, 9 May 2019 15:38:29 +0200	[thread overview]
Message-ID: <20190509153829.06319d0c@kitsune.suse.cz> (raw)
In-Reply-To: <20190509121923.8339-1-pmladek@suse.com>

On Thu,  9 May 2019 14:19:23 +0200
Petr Mladek <pmladek@suse.com> wrote:

> The commit 3e5903eb9cff70730 ("vsprintf: Prevent crash when dereferencing
> invalid pointers") broke boot on several architectures. The common
> pattern is that probe_kernel_read() is not working during early
> boot because userspace access framework is not ready.
> 
> The check is only the best effort. Let's not rush with it during
> the early boot.
> 
> Details:
> 
> 1. Report on Power:
> 
> Kernel crashes very early during boot with with CONFIG_PPC_KUAP and
> CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG
> 
> The problem is the combination of some new code called via printk(),
> check_pointer() which calls probe_kernel_read(). That then calls
> allow_user_access() (PPC_KUAP) and that uses mmu_has_feature() too early
> (before we've patched features).

There is early_mmu_has_feature for this case. mmu_has_feature does not
work before patching so parts of kernel that can run before patching
must use the early_ variant which actually runs code reading the
feature bitmap to determine the answer.

Thanks

Michal

  parent reply	other threads:[~2019-05-09 13:38 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-09 12:19 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 [this message]
2019-05-09 13:46   ` David Laight
2019-05-10 10:21     ` Michael Ellerman
2019-05-10  4:32 ` Sergey Senozhatsky
     [not found]   ` <CAHk-=wiP+hwSqEW0dM6AYNWUR7jXDkeueq69et6ahfUgV7hC3w@mail.gmail.com>
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
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190509153829.06319d0c@kitsune.suse.cz \
    --to=msuchanek@suse.de \
    --cc=andriy.shevchenko@linux.intel.com \
    --cc=heiko.carstens@de.ibm.com \
    --cc=linux-arch@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-s390@vger.kernel.org \
    --cc=linux@rasmusvillemoes.dk \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=me@tobin.cc \
    --cc=mhocko@suse.cz \
    --cc=pmladek@suse.com \
    --cc=rostedt@goodmis.org \
    --cc=schwidefsky@de.ibm.com \
    --cc=sergey.senozhatsky.work@gmail.com \
    --cc=sergey.senozhatsky@gmail.com \
    --cc=sfr@ozlabs.org \
    --cc=torvalds@linux-foundation.org \
    --subject='Re: [PATCH] vsprintf: Do not break early boot with probing addresses' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).