linux-stable.git/Documentation, branch v4.14.313

ALSA: hda/sigmatel: add pin overrides for Intel DP45SG motherboard

2023-04-20T10:02:11+00:00

commit c17f8fd31700392b1bb9e7b66924333568cb3700 upstream.

Like the other boards from the D*45* series, this one sets up the
outputs not quite correctly.

Signed-off-by: Oswald Buddenhagen 
Cc: 
Link: https://lore.kernel.org/r/20230405201220.2197826-1-oswald.buddenhagen@gmx.de
Signed-off-by: Takashi Iwai 
Signed-off-by: Greg Kroah-Hartman

Documentation/hw-vuln: Document the interaction between IBRS and STIBP

2023-03-11T15:26:46+00:00

commit e02b50ca442e88122e1302d4dbc1b71a4808c13f upstream.

Explain why STIBP is needed with legacy IBRS as currently implemented
(KERNEL_IBRS) and why STIBP is not needed when enhanced IBRS is enabled.

Fixes: 7c693f54c873 ("x86/speculation: Add spectre_v2=ibrs option to support Kernel IBRS")
Signed-off-by: KP Singh 
Signed-off-by: Borislav Petkov (AMD) 
Link: https://lore.kernel.org/r/20230227060541.1939092-2-kpsingh@kernel.org
Signed-off-by: Greg Kroah-Hartman

docs/scripts/gdb: add necessary make scripts_gdb step

2023-03-11T15:26:42+00:00

[ Upstream commit 6b219431037bf98c9efd49716aea9b68440477a3 ]

In order to debug the kernel successfully with gdb you need to run
'make scripts_gdb' nowadays.

This was changed with the following commit:

Commit 67274c083438340ad16c ("scripts/gdb: delay generation of gdb
constants.py")

In order to have a complete guide for beginners this remark
should be added to the offial documentation.

Signed-off-by: Jakob Koschel 
Link: https://lore.kernel.org/r/20230112-documentation-gdb-v2-1-292785c43dc9@gmail.com
Signed-off-by: Jonathan Corbet 
Signed-off-by: Sasha Levin

docs: Fix path paste-o for /sys/kernel/warn_count

2023-02-06T06:46:35+00:00

commit 00dd027f721e0458418f7750d8a5a664ed3e5994 upstream.

Running "make htmldocs" shows that "/sys/kernel/oops_count" was
duplicated. This should have been "warn_count":

  Warning: /sys/kernel/oops_count is defined 2 times:
  ./Documentation/ABI/testing/sysfs-kernel-warn_count:0
  ./Documentation/ABI/testing/sysfs-kernel-oops_count:0

Fix the typo.

Reported-by: kernel test robot 
Link: https://lore.kernel.org/linux-doc/202212110529.A3Qav8aR-lkp@intel.com
Fixes: 8b05aa263361 ("panic: Expose "warn_count" to sysfs")
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Kees Cook 
Signed-off-by: Eric Biggers 
Signed-off-by: Greg Kroah-Hartman

panic: Expose "warn_count" to sysfs

2023-02-06T06:46:35+00:00

commit 8b05aa26336113c4cea25f1c333ee8cd4fc212a6 upstream.

Since Warn count is now tracked and is a fairly interesting signal, add
the entry /sys/kernel/warn_count to expose it to userspace.

Cc: Petr Mladek 
Cc: Andrew Morton 
Cc: tangmeng 
Cc: "Guilherme G. Piccoli" 
Cc: Sebastian Andrzej Siewior 
Cc: Tiezhu Yang 
Reviewed-by: Luis Chamberlain 
Signed-off-by: Kees Cook 
Link: https://lore.kernel.org/r/20221117234328.594699-6-keescook@chromium.org
Signed-off-by: Eric Biggers 
Signed-off-by: Greg Kroah-Hartman

panic: Introduce warn_limit

2023-02-06T06:46:35+00:00

commit 9fc9e278a5c0b708eeffaf47d6eb0c82aa74ed78 upstream.

Like oops_limit, add warn_limit for limiting the number of warnings when
panic_on_warn is not set.

Cc: Jonathan Corbet 
Cc: Andrew Morton 
Cc: Baolin Wang 
Cc: "Jason A. Donenfeld" 
Cc: Eric Biggers 
Cc: Huang Ying 
Cc: Petr Mladek 
Cc: tangmeng 
Cc: "Guilherme G. Piccoli" 
Cc: Tiezhu Yang 
Cc: Sebastian Andrzej Siewior 
Cc: linux-doc@vger.kernel.org
Reviewed-by: Luis Chamberlain 
Signed-off-by: Kees Cook 
Link: https://lore.kernel.org/r/20221117234328.594699-5-keescook@chromium.org
Signed-off-by: Eric Biggers 
Signed-off-by: Greg Kroah-Hartman

exit: Allow oops_limit to be disabled

2023-02-06T06:46:34+00:00

commit de92f65719cd672f4b48397540b9f9eff67eca40 upstream.

In preparation for keeping oops_limit logic in sync with warn_limit,
have oops_limit == 0 disable checking the Oops counter.

Cc: Jann Horn 
Cc: Jonathan Corbet 
Cc: Andrew Morton 
Cc: Baolin Wang 
Cc: "Jason A. Donenfeld" 
Cc: Eric Biggers 
Cc: Huang Ying 
Cc: "Eric W. Biederman" 
Cc: Arnd Bergmann 
Cc: linux-doc@vger.kernel.org
Signed-off-by: Kees Cook 
Signed-off-by: Eric Biggers 
Signed-off-by: Greg Kroah-Hartman

exit: Expose "oops_count" to sysfs

2023-02-06T06:46:34+00:00

commit 9db89b41117024f80b38b15954017fb293133364 upstream.

Since Oops count is now tracked and is a fairly interesting signal, add
the entry /sys/kernel/oops_count to expose it to userspace.

Cc: "Eric W. Biederman" 
Cc: Jann Horn 
Cc: Arnd Bergmann 
Reviewed-by: Luis Chamberlain 
Signed-off-by: Kees Cook 
Link: https://lore.kernel.org/r/20221117234328.594699-3-keescook@chromium.org
Signed-off-by: Eric Biggers 
Signed-off-by: Greg Kroah-Hartman

exit: Put an upper limit on how often we can oops

2023-02-06T06:46:34+00:00

commit d4ccd54d28d3c8598e2354acc13e28c060961dbb upstream.

Many Linux systems are configured to not panic on oops; but allowing an
attacker to oops the system **really** often can make even bugs that look
completely unexploitable exploitable (like NULL dereferences and such) if
each crash elevates a refcount by one or a lock is taken in read mode, and
this causes a counter to eventually overflow.

The most interesting counters for this are 32 bits wide (like open-coded
refcounts that don't use refcount_t). (The ldsem reader count on 32-bit
platforms is just 16 bits, but probably nobody cares about 32-bit platforms
that much nowadays.)

So let's panic the system if the kernel is constantly oopsing.

The speed of oopsing 2^32 times probably depends on several factors, like
how long the stack trace is and which unwinder you're using; an empirically
important one is whether your console is showing a graphical environment or
a text console that oopses will be printed to.
In a quick single-threaded benchmark, it looks like oopsing in a vfork()
child with a very short stack trace only takes ~510 microseconds per run
when a graphical console is active; but switching to a text console that
oopses are printed to slows it down around 87x, to ~45 milliseconds per
run.
(Adding more threads makes this faster, but the actual oops printing
happens under &die_lock on x86, so you can maybe speed this up by a factor
of around 2 and then any further improvement gets eaten up by lock
contention.)

It looks like it would take around 8-12 days to overflow a 32-bit counter
with repeated oopsing on a multi-core X86 system running a graphical
environment; both me (in an X86 VM) and Seth (with a distro kernel on
normal hardware in a standard configuration) got numbers in that ballpark.

12 days aren't *that* short on a desktop system, and you'd likely need much
longer on a typical server system (assuming that people don't run graphical
desktop environments on their servers), and this is a *very* noisy and
violent approach to exploiting the kernel; and it also seems to take orders
of magnitude longer on some machines, probably because stuff like EFI
pstore will slow it down a ton if that's active.

Signed-off-by: Jann Horn 
Link: https://lore.kernel.org/r/20221107201317.324457-1-jannh@google.com
Reviewed-by: Luis Chamberlain 
Signed-off-by: Kees Cook 
Link: https://lore.kernel.org/r/20221117234328.594699-2-keescook@chromium.org
Signed-off-by: Eric Biggers 
Signed-off-by: Greg Kroah-Hartman

docs: Fix the docs build with Sphinx 6.0

2023-01-18T08:26:42+00:00

commit 0283189e8f3d0917e2ac399688df85211f48447b upstream.

Sphinx 6.0 removed the execfile_() function, which we use as part of the
configuration process.  They *did* warn us...  Just open-code the
functionality as is done in Sphinx itself.

Tested (using SPHINX_CONF, since this code is only executed with an
alternative config file) on various Sphinx versions from 2.5 through 6.0.

Reported-by: Martin Liška 
Cc: stable@vger.kernel.org
Signed-off-by: Jonathan Corbet 
Signed-off-by: Greg Kroah-Hartman