LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: Andrew Morton <akpm@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Dmitry Vyukov <dvyukov@google.com>
Cc: Matthew Garrett <mjg59@google.com>,
	Andi Kleen <ak@linux.intel.com>,
	"Theodore Y . Ts'o" <tytso@mit.edu>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Petr Mladek <pmladek@suse.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Arnd Bergmann <arnd@arndb.de>, Jiri Slaby <jslaby@suse.com>,
	Peter Zijlstra <peterz@infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	syzkaller@googlegroups.com,
	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Subject: [PATCH v4 1/3] Add kernel config option for twisting kernel behavior.
Date: Tue, 21 Apr 2020 22:19:49 +0900
Message-ID: <20200421131951.4948-1-penguin-kernel@I-love.SAKURA.ne.jp> (raw)

Existing kernel config options are defined based on "whether you want to
enable this module/feature or not". And such granularity is sometimes
too rough-grained for fuzzing tools which try to find bugs inside each
module/feature.

While syzkaller (one of fuzzing tools) is finding many bugs, sometimes
syzkaller examines stupid operations. Some examples of such operations
are: changing console loglevel which in turn makes it impossible to get
kernel messages when a crash happens, freezing filesystems which in turn
causes khungtaskd to needlessly complain, programmatically sending
Ctrl-Alt-Del which in turn causes the system to needlessly reboot.
Currently we prevent syzkaller from examining stupid operations by
blacklisting syscall arguments and/or disabling whole functionality
using existing kernel config options. But such approach is difficult to
maintain and needlessly prevents fuzzers from testing kernel code. [1]

We want fuzzers to test as much coverage as possible while we want
fuzzers not to try stupid operations. To achieve this goal, we want
cooperation from kernel side, and build-time branching (i.e. kernel
config options) will be the simplest and the most reliable.

Therefore, this patch introduces a kernel config option which allows
selecting fine-grained kernel config options for twisting kernel's
behavior. Each fine-grained kernel config option will be added by future
patches. For ease of management, grouping kernel config options for
allowing e.g. syzkaller to select all fine-grained kernel config options
which e.g. syzkaller wants would be added by future patches.

[1] https://lkml.kernel.org/r/CACT4Y+a6KExbggs4mg8pvoD554PcDqQNW4sM15X-tc=YONCzYw@mail.gmail.com

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
 lib/Kconfig.debug |  2 ++
 lib/Kconfig.twist | 13 +++++++++++++
 2 files changed, 15 insertions(+)
 create mode 100644 lib/Kconfig.twist

Changes since v3 ( https://lkml.kernel.org/r/20200413063317.7164-1-penguin-kernel@I-love.SAKURA.ne.jp ):
  Use "twist" instead of "tweak".
  Add an instance of fine-grained kernel config option as patch 2 of 3.
  Add a grouping kernel config option for syzkaller as patch 3 of 3.

Changes since v2 ( https://lkml.kernel.org/r/20200307135822.3894-1-penguin-kernel@I-love.SAKURA.ne.jp ):
  Reduce the role of this kernel config option from "enable everything
  which would be useful for fuzz testing" to "simply serve as a gate for
  hiding individual kernel config option", for we should use individual
  kernel config option for tweaking individual kernel behavior.

Changes since v1 ( https://lkml.kernel.org/r/20191216095955.9886-1-penguin-kernel@I-love.SAKURA.ne.jp ):
  Drop users of this kernel config option.
  Update patch description.

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 21d9c5f6e7ec..e6162595ef9d 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2225,4 +2225,6 @@ config HYPERV_TESTING
 
 endmenu # "Kernel Testing and Coverage"
 
+source "lib/Kconfig.twist"
+
 endmenu # Kernel hacking
diff --git a/lib/Kconfig.twist b/lib/Kconfig.twist
new file mode 100644
index 000000000000..a5ce0db67f28
--- /dev/null
+++ b/lib/Kconfig.twist
@@ -0,0 +1,13 @@
+menuconfig TWIST_KERNEL_BEHAVIOR
+	bool "Twist kernel behavior"
+	help
+	  Saying Y here allows modifying kernel behavior via kernel
+	  config options which will become visible by selecting this
+	  config option. Since these kernel config options are intended
+	  for helping e.g. fuzz testing, behavior twisted by this kernel
+	  option might be unstable. Userspace applications should not
+	  count on this option being selected.
+
+if TWIST_KERNEL_BEHAVIOR
+
+endif # TWIST_KERNEL_BEHAVIOR
-- 
2.18.2


             reply index

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-21 13:19 Tetsuo Handa [this message]
2020-04-21 13:19 ` [PATCH v4 2/3] twist: Allow disabling k_spec() function in drivers/tty/vt/keyboard.c Tetsuo Handa
2020-04-21 13:19 ` [PATCH v4 3/3] twist: Add option for selecting twist options for syzkaller's testing Tetsuo Handa
2020-04-21 16:00   ` Dmitry Vyukov

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200421131951.4948-1-penguin-kernel@I-love.SAKURA.ne.jp \
    --to=penguin-kernel@i-love.sakura.ne.jp \
    --cc=ak@linux.intel.com \
    --cc=akpm@linux-foundation.org \
    --cc=arnd@arndb.de \
    --cc=dvyukov@google.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=jslaby@suse.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mjg59@google.com \
    --cc=peterz@infradead.org \
    --cc=pmladek@suse.com \
    --cc=rostedt@goodmis.org \
    --cc=sergey.senozhatsky@gmail.com \
    --cc=syzkaller@googlegroups.com \
    --cc=torvalds@linux-foundation.org \
    --cc=tytso@mit.edu \
    --cc=viro@zeniv.linux.org.uk \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
	git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git