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Thomas Gleixner 75dc252e70 debugobject: Prevent init race with static objects 
[ Upstream commit 63a759694e ]

Statically initialized objects are usually not initialized via the init()
function of the subsystem. They are special cased and the subsystem
provides a function to validate whether an object which is not yet tracked
by debugobjects is statically initialized. This means the object is started
to be tracked on first use, e.g. activation.

This works perfectly fine, unless there are two concurrent operations on
that object. Schspa decoded the problem:

T0 	          	    	    T1

debug_object_assert_init(addr)
  lock_hash_bucket()
  obj = lookup_object(addr);
  if (!obj) {
  	unlock_hash_bucket();
	- > preemption
			            lock_subsytem_object(addr);
				      activate_object(addr)
				      lock_hash_bucket();
				      obj = lookup_object(addr);
				      if (!obj) {
				    	unlock_hash_bucket();
					if (is_static_object(addr))
					   init_and_track(addr);
				      lock_hash_bucket();
				      obj = lookup_object(addr);
				      obj->state = ACTIVATED;
				      unlock_hash_bucket();

				    subsys function modifies content of addr,
				    so static object detection does
				    not longer work.

				    unlock_subsytem_object(addr);

        if (is_static_object(addr)) <- Fails

	  debugobject emits a warning and invokes the fixup function which
	  reinitializes the already active object in the worst case.

This race exists forever, but was never observed until mod_timer() got a
debug_object_assert_init() added which is outside of the timer base lock
held section right at the beginning of the function to cover the lockless
early exit points too.

Rework the code so that the lookup, the static object check and the
tracking object association happens atomically under the hash bucket
lock. This prevents the issue completely as all callers are serialized on
the hash bucket lock and therefore cannot observe inconsistent state.

Fixes: 3ac7fe5a4a ("infrastructure to debug (dynamic) objects")
Reported-by: syzbot+5093ba19745994288b53@syzkaller.appspotmail.com
Debugged-by: Schspa Shi <schspa@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://syzkaller.appspot.com/bug?id=22c8a5938eab640d1c6bcc0e3dc7be519d878462
Link: https://lore.kernel.org/lkml/20230303161906.831686-1-schspa@gmail.com
Link: https://lore.kernel.org/r/87zg7dzgao.ffs@tglx
Signed-off-by: Sasha Levin <sashal@kernel.org>
2023-05-11 23:17:10 +09:00
arch arm64: kgdb: Set PSTATE.SS to 1 to re-enable single-step 2023-05-11 23:17:09 +09:00
block blk-crypto: make blk_crypto_evict_key() more robust 2023-05-11 23:16:48 +09:00
certs Kbuild updates for v6.3 2023-02-26 11:53:25 -08:00
crypto crypto: testmgr - fix RNG performance in fuzz tests 2023-05-11 23:16:50 +09:00
Documentation ASoC: dt-bindings: qcom,lpass-rx-macro: correct minItems for clocks 2023-05-11 23:16:54 +09:00
drivers media: mediatek: vcodec: add remove function for decoder platform driver 2023-05-11 23:17:09 +09:00
fs erofs: fix potential overflow calculating xattr_isize 2023-05-11 23:16:57 +09:00
include ACPI: processor: Fix evaluating _PDC method when running as Xen dom0 2023-05-11 23:17:03 +09:00
init gcc: disable '-Warray-bounds' for gcc-13 too 2023-04-23 09:56:20 -07:00
io_uring io_uring-6.3-2023-04-14 2023-04-15 10:29:53 -07:00
ipc Merge branch 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2023-02-24 19:20:07 -08:00
kernel rcu: Fix missing TICK_DEP_MASK_RCU_EXP dependency check 2023-05-11 23:16:56 +09:00
lib debugobject: Prevent init race with static objects 2023-05-11 23:17:10 +09:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm kasan: hw_tags: avoid invalid virt_to_page() 2023-05-11 23:16:55 +09:00
net bluetooth: Perform careful capability checks in hci_sock_ioctl() 2023-05-01 08:32:25 +09:00
rust rust: allow to use INIT_STACK_ALL_ZERO 2023-04-19 19:34:43 +02:00
samples LoongArch changes for v6.3 2023-03-01 09:27:00 -08:00
scripts Kbuild fixes for v6.3 (4th) 2023-04-23 08:22:25 -07:00
security selinux: ensure av_permissions.h is built when needed 2023-05-11 23:16:57 +09:00
sound ASoC: codecs: wcd938x: fix accessing regmap on unattached devices 2023-05-11 23:16:54 +09:00
tools tools/x86/kcpuid: Fix avx512bw and avx512lvl fields in Fn00000007 2023-05-11 23:16:58 +09:00
usr initramfs: Check negative timestamp to prevent broken cpio archive 2023-04-16 17:37:01 +09:00
virt KVM: PPC: Make KVM_CAP_IRQFD_RESAMPLE platform dependent 2023-03-31 11:19:05 -04:00
.clang-format cpumask: re-introduce constant-sized cpumask optimizations 2023-03-05 14:30:34 -08:00
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for *.dtso files 2023-02-26 15:28:23 +09:00
.gitignore kbuild: rpm-pkg: move source components to rpmbuild/SOURCES 2023-03-16 22:45:56 +09:00
.mailmap Networking fixes for 6.3-rc8, including fixes from netfilter and bpf 2023-04-20 11:03:51 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS There is no particular theme here - mainly quick hits all over the tree. 2023-02-23 17:55:40 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: Resume MPTCP co-maintainer role 2023-04-19 18:10:24 -07:00
Makefile Linux 6.3.1 2023-05-01 08:32:26 +09:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.