linux-toradex.git/kernel/panic.c, branch v4.16-rc4

kernel/panic.c: add TAINT_AUX

2017-11-18T00:10:04+00:00

This is the gist of a patch which we've been forward-porting in our
kernels for a long time now and it probably would make a good sense to
have such TAINT_AUX flag upstream which can be used by each distro etc,
how they see fit.  This way, we won't need to forward-port a distro-only
version indefinitely.

Add an auxiliary taint flag to be used by distros and others.  This
obviates the need to forward-port whatever internal solutions people
have in favor of a single flag which they can map arbitrarily to a
definition of their pleasing.

The "X" mnemonic could also mean eXternal, which would be taint from a
distro or something else but not the upstream kernel.  We will use it to
mark modules for which we don't provide support.  I.e., a really
eXternal module.

Link: http://lkml.kernel.org/r/20170911134533.dp5mtyku5bongx4c@pd.tnic
Signed-off-by: Borislav Petkov 
Cc: Kees Cook 
Cc: Jessica Yu 
Cc: Peter Zijlstra 
Cc: Jiri Slaby 
Cc: Jiri Olsa 
Cc: Michal Marek 
Cc: Jiri Kosina 
Cc: Takashi Iwai 
Cc: Petr Mladek 
Cc: Jeff Mahoney 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bug: fix "cut here" location for __WARN_TAINT architectures

2017-11-18T00:10:01+00:00

Prior to v4.11, x86 used warn_slowpath_fmt() for handling WARN()s.
After WARN() was moved to using UD0 on x86, the warning text started
appearing _before_ the "cut here" line.  This appears to have been a
long-standing bug on architectures that used __WARN_TAINT, but it didn't
get fixed.

v4.11 and earlier on x86:

  ------------[ cut here ]------------
  WARNING: CPU: 0 PID: 2956 at drivers/misc/lkdtm_bugs.c:65 lkdtm_WARNING+0x21/0x30
  This is a warning message
  Modules linked in:

v4.12 and later on x86:

  This is a warning message
  ------------[ cut here ]------------
  WARNING: CPU: 1 PID: 2982 at drivers/misc/lkdtm_bugs.c:68 lkdtm_WARNING+0x15/0x20
  Modules linked in:

With this fix:

  ------------[ cut here ]------------
  This is a warning message
  WARNING: CPU: 3 PID: 3009 at drivers/misc/lkdtm_bugs.c:67 lkdtm_WARNING+0x15/0x20

Since the __FILE__ reporting happens as part of the UD0 handler, it
isn't trivial to move the message to after the WARNING line, but at
least we can fix the position of the "cut here" line so all the various
logging tools will start including the actual runtime warning message
again, when they follow the instruction and "cut here".

Link: http://lkml.kernel.org/r/1510100869-73751-4-git-send-email-keescook@chromium.org
Fixes: 9a93848fe787 ("x86/debug: Implement __WARN() using UD0")
Signed-off-by: Kees Cook 
Cc: Peter Zijlstra (Intel) 
Cc: Josh Poimboeuf 
Cc: Fengguang Wu 
Cc: Arnd Bergmann 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bug: define the "cut here" string in a single place

2017-11-18T00:10:01+00:00

The "cut here" string is used in a few paths.  Define it in a single
place.

Link: http://lkml.kernel.org/r/1510100869-73751-3-git-send-email-keescook@chromium.org
Signed-off-by: Kees Cook 
Cc: Arnd Bergmann 
Cc: Fengguang Wu 
Cc: Ingo Molnar 
Cc: Josh Poimboeuf 
Cc: Peter Zijlstra (Intel) 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kernel debug: support resetting WARN_ONCE for all architectures

2017-11-18T00:10:01+00:00

Some architectures store the WARN_ONCE state in the flags field of the
bug_entry.  Clear that one too when resetting once state through
/sys/kernel/debug/clear_warn_once

Pointed out by Michael Ellerman

Improves the earlier patch that add clear_warn_once.

[ak@linux.intel.com: add a missing ifdef CONFIG_MODULES]
  Link: http://lkml.kernel.org/r/20171020170633.9593-1-andi@firstfloor.org
[akpm@linux-foundation.org: fix unused var warning]
[akpm@linux-foundation.org: Use 0200 for clear_warn_once file, per mpe]
[akpm@linux-foundation.org: clear BUGFLAG_DONE in clear_once_table(), per mpe]
Link: http://lkml.kernel.org/r/20171019204642.7404-1-andi@firstfloor.org
Signed-off-by: Andi Kleen 
Tested-by: Michael Ellerman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kernel debug: support resetting WARN*_ONCE

2017-11-18T00:10:00+00:00

I like _ONCE warnings because it's guaranteed that they don't flood the
log.

During testing I find it useful to reset the state of the once warnings,
so that I can rerun tests and see if they trigger again, or can
guarantee that a test run always hits the same warnings.

This patch adds a debugfs interface to reset all the _ONCE warnings so
that they appear again:

  echo 1 > /sys/kernel/debug/clear_warn_once

This is implemented by putting all the warning booleans into a special
section, and clearing it.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20171017221455.6740-1-andi@firstfloor.org
Signed-off-by: Andi Kleen 
Tested-by: Michael Ellerman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

locking/refcounts, x86/asm: Implement fast refcount overflow protection

2017-08-17T08:40:26+00:00

This implements refcount_t overflow protection on x86 without a noticeable
performance impact, though without the fuller checking of REFCOUNT_FULL.

This is done by duplicating the existing atomic_t refcount implementation
but with normally a single instruction added to detect if the refcount
has gone negative (e.g. wrapped past INT_MAX or below zero). When detected,
the handler saturates the refcount_t to INT_MIN / 2. With this overflow
protection, the erroneous reference release that would follow a wrap back
to zero is blocked from happening, avoiding the class of refcount-overflow
use-after-free vulnerabilities entirely.

Only the overflow case of refcounting can be perfectly protected, since
it can be detected and stopped before the reference is freed and left to
be abused by an attacker. There isn't a way to block early decrements,
and while REFCOUNT_FULL stops increment-from-zero cases (which would
be the state _after_ an early decrement and stops potential double-free
conditions), this fast implementation does not, since it would require
the more expensive cmpxchg loops. Since the overflow case is much more
common (e.g. missing a "put" during an error path), this protection
provides real-world protection. For example, the two public refcount
overflow use-after-free exploits published in 2016 would have been
rendered unexploitable:

  http://perception-point.io/2016/01/14/analysis-and-exploitation-of-a-linux-kernel-vulnerability-cve-2016-0728/

  http://cyseclabs.com/page?n=02012016

This implementation does, however, notice an unchecked decrement to zero
(i.e. caller used refcount_dec() instead of refcount_dec_and_test() and it
resulted in a zero). Decrements under zero are noticed (since they will
have resulted in a negative value), though this only indicates that a
use-after-free may have already happened. Such notifications are likely
avoidable by an attacker that has already exploited a use-after-free
vulnerability, but it's better to have them reported than allow such
conditions to remain universally silent.

On first overflow detection, the refcount value is reset to INT_MIN / 2
(which serves as a saturation value) and a report and stack trace are
produced. When operations detect only negative value results (such as
changing an already saturated value), saturation still happens but no
notification is performed (since the value was already saturated).

On the matter of races, since the entire range beyond INT_MAX but before
0 is negative, every operation at INT_MIN / 2 will trap, leaving no
overflow-only race condition.

As for performance, this implementation adds a single "js" instruction
to the regular execution flow of a copy of the standard atomic_t refcount
operations. (The non-"and_test" refcount_dec() function, which is uncommon
in regular refcount design patterns, has an additional "jz" instruction
to detect reaching exactly zero.) Since this is a forward jump, it is by
default the non-predicted path, which will be reinforced by dynamic branch
prediction. The result is this protection having virtually no measurable
change in performance over standard atomic_t operations. The error path,
located in .text.unlikely, saves the refcount location and then uses UD0
to fire a refcount exception handler, which resets the refcount, handles
reporting, and returns to regular execution. This keeps the changes to
.text size minimal, avoiding return jumps and open-coded calls to the
error reporting routine.

Example assembly comparison:

refcount_inc() before:

  .text:
  ffffffff81546149:       f0 ff 45 f4             lock incl -0xc(%rbp)

refcount_inc() after:

  .text:
  ffffffff81546149:       f0 ff 45 f4             lock incl -0xc(%rbp)
  ffffffff8154614d:       0f 88 80 d5 17 00       js     ffffffff816c36d3
  ...
  .text.unlikely:
  ffffffff816c36d3:       48 8d 4d f4             lea    -0xc(%rbp),%rcx
  ffffffff816c36d7:       0f ff                   (bad)

These are the cycle counts comparing a loop of refcount_inc() from 1
to INT_MAX and back down to 0 (via refcount_dec_and_test()), between
unprotected refcount_t (atomic_t), fully protected REFCOUNT_FULL
(refcount_t-full), and this overflow-protected refcount (refcount_t-fast):

  2147483646 refcount_inc()s and 2147483647 refcount_dec_and_test()s:
		    cycles		protections
  atomic_t           82249267387	none
  refcount_t-fast    82211446892	overflow, untested dec-to-zero
  refcount_t-full   144814735193	overflow, untested dec-to-zero, inc-from-zero

This code is a modified version of the x86 PAX_REFCOUNT atomic_t
overflow defense from the last public patch of PaX/grsecurity, based
on my understanding of the code. Changes or omissions from the original
code are mine and don't reflect the original grsecurity/PaX code. Thanks
to PaX Team for various suggestions for improvement for repurposing this
code to be a refcount-only protection.

Signed-off-by: Kees Cook 
Reviewed-by: Josh Poimboeuf 
Cc: Alexey Dobriyan 
Cc: Andrew Morton 
Cc: Arnd Bergmann 
Cc: Christoph Hellwig 
Cc: David S. Miller 
Cc: Davidlohr Bueso 
Cc: Elena Reshetova 
Cc: Eric Biggers 
Cc: Eric W. Biederman 
Cc: Greg KH 
Cc: Hans Liljestrand 
Cc: James Bottomley 
Cc: Jann Horn 
Cc: Linus Torvalds 
Cc: Manfred Spraul 
Cc: Peter Zijlstra 
Cc: Rik van Riel 
Cc: Serge E. Hallyn 
Cc: Thomas Gleixner 
Cc: arozansk@redhat.com
Cc: axboe@kernel.dk
Cc: kernel-hardening@lists.openwall.com
Cc: linux-arch 
Link: http://lkml.kernel.org/r/20170815161924.GA133115@beast
Signed-off-by: Ingo Molnar

sched/headers: Prepare for new header dependencies before moving code to

2017-03-02T07:42:34+00:00

We are going to split  out of , which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder  file that just
maps to  to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.

Acked-by: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

sparc64: Send break twice from console to return to boot prom

2017-02-23T16:27:24+00:00

Now we can also jump to boot prom from sunhv console by sending
break twice on console for both running and panicked kernel
cases.

Signed-off-by: Vijay Kumar 
Signed-off-by: David S. Miller

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

2017-02-23T01:33:34+00:00

Pull printk updates from Petr Mladek:

 - Add Petr Mladek, Sergey Senozhatsky as printk maintainers, and Steven
   Rostedt as the printk reviewer. This idea came up after the
   discussion about printk issues at Kernel Summit. It was formulated
   and discussed at lkml[1].

 - Extend a lock-less NMI per-cpu buffers idea to handle recursive
   printk() calls by Sergey Senozhatsky[2]. It is the first step in
   sanitizing printk as discussed at Kernel Summit.

   The change allows to see messages that would normally get ignored or
   would cause a deadlock.

   Also it allows to enable lockdep in printk(). This already paid off.
   The testing in linux-next helped to discover two old problems that
   were hidden before[3][4].

 - Remove unused parameter by Sergey Senozhatsky. Clean up after a past
   change.

[1] http://lkml.kernel.org/r/1481798878-31898-1-git-send-email-pmladek@suse.com
[2] http://lkml.kernel.org/r/20161227141611.940-1-sergey.senozhatsky@gmail.com
[3] http://lkml.kernel.org/r/20170215044332.30449-1-sergey.senozhatsky@gmail.com
[4] http://lkml.kernel.org/r/20170217015932.11898-1-sergey.senozhatsky@gmail.com

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
  printk: drop call_console_drivers() unused param
  printk: convert the rest to printk-safe
  printk: remove zap_locks() function
  printk: use printk_safe buffers in printk
  printk: report lost messages in printk safe/nmi contexts
  printk: always use deferred printk when flush printk_safe lines
  printk: introduce per-cpu safe_print seq buffer
  printk: rename nmi.c and exported api
  printk: use vprintk_func in vprintk()
  MAINTAINERS: Add printk maintainers

printk: rename nmi.c and exported api

2017-02-08T10:02:33+00:00

A preparation patch for printk_safe work. No functional change.
- rename nmi.c to print_safe.c
- add `printk_safe' prefix to some (which used both by printk-safe
  and printk-nmi) of the exported functions.

Link: http://lkml.kernel.org/r/20161227141611.940-3-sergey.senozhatsky@gmail.com
Cc: Andrew Morton 
Cc: Linus Torvalds 
Cc: Jan Kara 
Cc: Tejun Heo 
Cc: Calvin Owens 
Cc: Steven Rostedt 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Andy Lutomirski 
Cc: Peter Hurley 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Sergey Senozhatsky 
Signed-off-by: Petr Mladek