[PATCH -v4 0/2] printk.devkmsg: Ratelimit it by default

[Borislav Petkov]

From: Borislav Petkov <bp@xxxxxxx>

Hi all,

sorry for spamming so quickly again and not waiting for a week before
resubmitting but I believe the stuff is ready for 4.8.

So here's v4 with all the minor review comments addressed.


Changelog:
----------

v3:

here's v3 integrating Ingo's comments. The thing is called
printk.devkmsg= or printk_devkmsg now, depending on cmdline option or
sysctl.


v2:

here's v2 with the requested sysctl option kernel.printk_kmsg and
locking of the setting when printk.kmsg= is supplied on the command
line.

Patch 1 is unchanged.

Patch 2 has grown the sysctl addition.

v1:

Rostedt is busy so I took Linus' old patch and Steven's last v2 and
split and extended them with the comments people had on the last thread:

https://lkml.kernel.org/r/20160425145606.598329f2@xxxxxxxxxxxxxxxxxx

I hope, at least.

So it is ratelimiting by default, with "on" and "off" cmdline options. I
called the option somewhat a bit shorter too: "printk.kmsg"

The current use cases of this and of which I'm aware are:

* debug the kernel and thus shut up all interfering input from
userspace, i.e. boot with "printk.kmsg=off"

* debug userspace (and by that I mean systemd) by booting with
"printk.kmsg=on" so that the ratelimiting is disabled and the kernel log
gets all the spew.

Thoughts?

Please queue,
thanks.

Borislav Petkov (2):
  ratelimit: Extend to print suppressed messages on release
  printk: Add kernel parameter to control writes to /dev/kmsg

 Documentation/kernel-parameters.txt |  6 +++
 Documentation/sysctl/kernel.txt     | 14 ++++++
 include/linux/printk.h              |  7 +++
 include/linux/ratelimit.h           | 38 +++++++++++++---
 kernel/printk/printk.c              | 86 +++++++++++++++++++++++++++++++++----
 kernel/sysctl.c                     |  9 ++++
 lib/ratelimit.c                     | 10 +++--
 7 files changed, 153 insertions(+), 17 deletions(-)

-- 
2.7.3