linux-stable.git/Documentation/admin-guide/sysctl, branch linux-5.15.y

Documentation: sysctl: align cells in second content column

2023-10-25T09:58:54+00:00

commit 1faa34672f8a17a3e155e74bde9648564e9480d6 upstream.

Stephen Rothwell reported htmldocs warning when merging net-next tree:

Documentation/admin-guide/sysctl/net.rst:37: WARNING: Malformed table.
Text in column margin in table line 4.

========= =================== = ========== ==================
Directory Content               Directory  Content
========= =================== = ========== ==================
802       E802 protocol         mptcp     Multipath TCP
appletalk Appletalk protocol    netfilter Network Filter
ax25      AX25                  netrom     NET/ROM
bridge    Bridging              rose      X.25 PLP layer
core      General parameter     tipc      TIPC
ethernet  Ethernet protocol     unix      Unix domain sockets
ipv4      IP version 4          x25       X.25 protocol
ipv6      IP version 6
========= =================== = ========== ==================

The warning above is caused by cells in second "Content" column of
/proc/sys/net subdirectory table which are in column margin.

Align these cells against the column header to fix the warning.

Link: https://lore.kernel.org/linux-next/20220823134905.57ed08d5@canb.auug.org.au/
Fixes: 1202cdd665315c ("Remove DECnet support from kernel")
Reported-by: Stephen Rothwell 
Signed-off-by: Bagas Sanjaya 
Link: https://lore.kernel.org/r/20220824035804.204322-1-bagasdotme@gmail.com
Signed-off-by: Jakub Kicinski 
Cc: Ben Hutchings 
Signed-off-by: Greg Kroah-Hartman

Remove DECnet support from kernel

2023-06-21T13:59:15+00:00

commit 1202cdd665315c525b5237e96e0bedc76d7e754f upstream.

DECnet is an obsolete network protocol that receives more attention
from kernel janitors than users. It belongs in computer protocol
history museum not in Linux kernel.

It has been "Orphaned" in kernel since 2010. The iproute2 support
for DECnet was dropped in 5.0 release. The documentation link on
Sourceforge says it is abandoned there as well.

Leave the UAPI alone to keep userspace programs compiling.
This means that there is still an empty neighbour table
for AF_DECNET.

The table of /proc/sys/net entries was updated to match
current directories and reformatted to be alphabetical.

Signed-off-by: Stephen Hemminger 
Acked-by: David Ahern 
Acked-by: Nikolay Aleksandrov 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

panic: Introduce warn_limit

2023-02-01T07:27:22+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: Sasha Levin

exit: Allow oops_limit to be disabled

2023-02-01T07:27:21+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: Sasha Levin

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

2023-02-01T07:27:21+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: Sasha Levin

net: Fix data-races around netdev_max_backlog.

2022-08-31T15:16:42+00:00

[ Upstream commit 5dcd08cd19912892586c6082d56718333e2d19db ]

While reading netdev_max_backlog, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its readers.

While at it, we remove the unnecessary spaces in the doc.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima 
Signed-off-by: David S. Miller 
Signed-off-by: Sasha Levin

mm/pagealloc: sysctl: change watermark_scale_factor max limit to 30%

2022-07-29T15:25:11+00:00

[ Upstream commit 39c65a94cd9661532be150e88f8b02f4a6844a35 ]

For embedded systems with low total memory, having to run applications
with relatively large memory requirements, 10% max limitation for
watermark_scale_factor poses an issue of triggering direct reclaim every
time such application is started.  This results in slow application
startup times and bad end-user experience.

By increasing watermark_scale_factor max limit we allow vendors more
flexibility to choose the right level of kswapd aggressiveness for their
device and workload requirements.

Link: https://lkml.kernel.org/r/20211124193604.2758863-1-surenb@google.com
Signed-off-by: Suren Baghdasaryan 
Acked-by: Johannes Weiner 
Cc: Michal Hocko 
Cc: Lukas Middendorf 
Cc: Antti Palosaari 
Cc: Luis Chamberlain 
Cc: Kees Cook 
Cc: Iurii Zaikin 
Cc: Dave Hansen 
Cc: Vlastimil Babka 
Cc: Mel Gorman 
Cc: Jonathan Corbet 
Cc: Zhang Yi 
Cc: Fengfei Xi 
Cc: Mike Rapoport 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin

random: fix sysctl documentation nits

2022-05-30T07:29:12+00:00

commit 069c4ea6871c18bd368f27756e0f91ffb524a788 upstream.

A semicolon was missing, and the almost-alphabetical-but-not ordering
was confusing, so regroup these by category instead.

Signed-off-by: Jason A. Donenfeld 
Signed-off-by: Greg Kroah-Hartman

random: remove ifdef'd out interrupt bench

2022-05-30T07:29:06+00:00

commit 95e6060c20a7f5db60163274c5222a725ac118f9 upstream.

With tools like kbench9000 giving more finegrained responses, and this
basically never having been used ever since it was initially added,
let's just get rid of this. There *is* still work to be done on the
interrupt handler, but this really isn't the way it's being developed.

Cc: Theodore Ts'o 
Reviewed-by: Eric Biggers 
Reviewed-by: Dominik Brodowski 
Signed-off-by: Jason A. Donenfeld 
Signed-off-by: Greg Kroah-Hartman

random: always wake up entropy writers after extraction

2022-05-30T07:29:04+00:00

commit 489c7fc44b5740d377e8cfdbf0851036e493af00 upstream.

Now that POOL_BITS == POOL_MIN_BITS, we must unconditionally wake up
entropy writers after every extraction. Therefore there's no point of
write_wakeup_threshold, so we can move it to the dustbin of unused
compatibility sysctls. While we're at it, we can fix a small comparison
where we were waking up after <= min rather than < min.

Cc: Theodore Ts'o 
Suggested-by: Eric Biggers 
Reviewed-by: Eric Biggers 
Reviewed-by: Dominik Brodowski 
Signed-off-by: Jason A. Donenfeld 
Signed-off-by: Greg Kroah-Hartman