linux-toradex.git/kernel/printk, branch v4.14-rc7

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk

2017-09-08T04:00:52+00:00

Pull printk updates from Petr Mladek:

 - Do not allow use of freed init data and code even when boot consoles
   are forced to stay. Also check for the init memory more precisely.

 - Some code clean up by starting contributors.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
  printk: Clean up do_syslog() error handling
  printk/console: Enhance the check for consoles using init memory
  printk/console: Always disable boot consoles that use init memory before it is freed
  printk: Modify operators of printed_len and text_len

Revert "pstore: Honor dmesg_restrict sysctl on dmesg dumps"

2017-08-17T23:29:19+00:00

This reverts commit 68c4a4f8abc60c9440ede9cd123d48b78325f7a3, with
various conflict clean-ups.

The capability check required too much privilege compared to simple DAC
controls. A system builder was forced to have crash handler processes
run with CAP_SYSLOG which would give it the ability to read (and wipe)
the _current_ dmesg, which is much more access than being given access
only to the historical log stored in pstorefs.

With the prior commit to make the root directory 0750, the files are
protected by default but a system builder can now opt to give access
to a specific group (via chgrp on the pstorefs root directory) without
being forced to also give away CAP_SYSLOG.

Suggested-by: Nick Kralevich 
Signed-off-by: Kees Cook 
Reviewed-by: Petr Mladek 
Reviewed-by: Sergey Senozhatsky

printk: Clean up do_syslog() error handling

2017-08-15T14:28:16+00:00

The error variable in do_syslog() is preemptively set to the error code
before the error condition is checked, and then set to 0 if the error
condition is not encountered. This is not necessary, as it is likely
simpler to return immediately upon encountering the error condition. A
redundant set of the error variable to 0 is also removed.

This patch has been build-tested on x86_64, but not tested for
functionality.

Link: http://lkml.kernel.org/r/20170730033636.GA935@vostro
Cc: Steven Rostedt 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Nikitas Angelinas 
Reviewed-by: Sergey Senozhatsky 
Signed-off-by: Petr Mladek

printk/console: Enhance the check for consoles using init memory

2017-07-27T13:04:22+00:00

printk_late_init() is responsible for disabling boot consoles that
use init memory. It checks the address of struct console for this.

But this is not enough. For example, there are several early
consoles that have write() method in the init section and
struct console in the normal section. They are not disabled
and could cause fancy and hard to debug system states.

It is even more complicated by the macros EARLYCON_DECLARE() and
OF_EARLYCON_DECLARE() where various struct members are set at
runtime by the provided setup() function.

I have tried to reproduce this problem and forced the classic uart
early console to stay using keep_bootcon parameter. In particular
I used earlycon=uart,io,0x3f8 keep_bootcon console=ttyS0,115200.
The system did not boot:

[    1.570496] PM: Image not found (code -22)
[    1.570496] PM: Image not found (code -22)
[    1.571886] PM: Hibernation image not present or could not be loaded.
[    1.571886] PM: Hibernation image not present or could not be loaded.
[    1.576407] Freeing unused kernel memory: 2528K
[    1.577244] kernel tried to execute NX-protected page - exploit attempt? (uid: 0)

The double lines are caused by having both early uart console and
ttyS0 console enabled at the same time. The early console stopped
working when the init memory was freed. Fortunately, the invalid
call was caught by the NX-protexted page check and did not cause
any silent fancy problems.

This patch adds a check for many other addresses stored in
struct console. It omits setup() and match() that are used
only when the console is registered. Therefore they have
already been used at this point and there is no reason
to use them again.

Link: http://lkml.kernel.org/r/1500036673-7122-3-git-send-email-pmladek@suse.com
Cc: Steven Rostedt 
Cc: Andrew Morton 
Cc: Peter Zijlstra 
Cc: Matt Redfearn 
Cc: Greg Kroah-Hartman 
Cc: Jiri Slaby 
Cc: "David S. Miller" 
Cc: Alan Cox 
Cc: "Fabio M. Di Nitto" 
Cc: linux-serial@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Sergey Senozhatsky 
Signed-off-by: Petr Mladek

printk/console: Always disable boot consoles that use init memory before it is freed

2017-07-27T13:04:21+00:00

Commit 4c30c6f566c0 ("kernel/printk: do not turn off bootconsole in
printk_late_init() if keep_bootcon") added a check on keep_bootcon to
ensure that boot consoles were kept around until the real console is
registered.

This can lead to problems if the boot console data and code are in the
init section, since it can be freed before the boot console is
unregistered.

Commit 81cc26f2bd11 ("printk: only unregister boot consoles when
necessary") fixed this a better way. It allowed to keep boot consoles
that did not use init data. Unfortunately it did not remove the check
of keep_bootcon.

This can lead to crashes and weird panics when the bootconsole is
accessed after free, especially if page poisoning is in use and the
code / data have been overwritten with a poison value.

To prevent this, always free the boot console if it is within the init
section. In addition, print a warning about that the console is removed
prematurely.

Finally there is a new comment how to avoid the warning. It replaced
an explanation that duplicated a more comprehensive function
description few lines above.

Fixes: 4c30c6f566c0 ("kernel/printk: do not turn off bootconsole in printk_late_init() if keep_bootcon")
Link: http://lkml.kernel.org/r/1500036673-7122-2-git-send-email-pmladek@suse.com
Cc: Steven Rostedt 
Cc: Andrew Morton 
Cc: Peter Zijlstra 
Cc: Greg Kroah-Hartman 
Cc: Jiri Slaby 
Cc: "David S. Miller" 
Cc: Alan Cox 
Cc: "Fabio M. Di Nitto" 
Cc: linux-serial@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Matt Redfearn 
[pmladek@suse.com: print the warning, code and comments clean up]
Reviewed-by: Sergey Senozhatsky 
Signed-off-by: Petr Mladek

printk: Modify operators of printed_len and text_len

2017-07-27T13:04:21+00:00

With commit  ("printk: report lost messages in printk
safe/nmi contexts") and commit <8b1742c9c207> ("printk: remove zap_locks()
function"), it seems we can remove initialization, "=0", of text_len and
directly assign result of log_output to printed_len.

Link: http://lkml.kernel.org/r/1499755255-6258-1-git-send-email-vichy.kuo@gmail.com
Cc: rostedt@goodmis.org
Cc: linux-kernel@vger.kernel.org
Cc: joe@perches.com
Signed-off-by: Pierre Kuo 
Reviewed-by: Sergey Senozhatsky 
Signed-off-by: Petr Mladek

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk

2017-07-05T18:11:26+00:00

Pull printk updates from Petr Mladek:

 - Store printk() messages into the main log buffer directly even in NMI
   when the lock is available. It is the best effort to print even large
   chunk of text. It is handy, for example, when all ftrace messages are
   printed during the system panic in NMI.

 - Add missing annotations to calm down compiler warnings

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
  printk: add __printf attributes to internal functions
  printk: Use the main logbuf in NMI when logbuf_lock is available

Merge branch 'for-4.13' into for-linus

2017-07-03T13:33:39+00:00

Merge branch 'WIP.sched/core' into sched/core

2017-06-20T10:28:21+00:00

 Conflicts:
	kernel/sched/Makefile

Pick up the waitqueue related renames - it didn't get much feedback,
so it appears to be uncontroversial. Famous last words? ;-)

Signed-off-by: Ingo Molnar

printk: add __printf attributes to internal functions

2017-06-13T14:36:02+00:00

When compiling with -Wsuggest-attribute=format, gcc complains that some
functions in kernel/printk/printk_safe.c transmit their argument to
printf-like functions without having a printf attribute. Silence these
warnings by adding relevant __printf attributes.

Link: http://lkml.kernel.org/r/20170524054950.6722-1-nicolas.iooss_linux@m4x.org
Cc: Steven Rostedt 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Nicolas Iooss 
Reviewed-by: Sergey Senozhatsky 
Signed-off-by: Petr Mladek