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Thomas Gleixner fc2b20c092 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>
History 2023-05-11 23:03:16 +09:00
arch arm64: kgdb: Set PSTATE.SS to 1 to re-enable single-step 2023-05-11 23:03:16 +09:00
block blk-crypto: make blk_crypto_evict_key() more robust 2023-05-11 23:03:01 +09:00
certs certs: Fix build error when PKCS#11 URI contains semicolon 2023-02-09 11:28:11 +01:00
crypto crypto: api - Demote BUG_ON() in crypto_unregister_alg() to a WARN_ON() 2023-05-11 23:03:02 +09:00
Documentation ASoC: dt-bindings: qcom,lpass-rx-macro: correct minItems for clocks 2023-05-11 23:03:05 +09:00
drivers media: mediatek: vcodec: add remove function for decoder platform driver 2023-05-11 23:03:16 +09:00
fs erofs: fix potential overflow calculating xattr_isize 2023-05-11 23:03:07 +09:00
include ACPI: processor: Fix evaluating _PDC method when running as Xen dom0 2023-05-11 23:03:11 +09:00
init gcc: disable '-Warray-bounds' for gcc-13 too 2023-04-26 14:28:43 +02:00
io_uring io_uring: fix memory leak when removing provided buffers 2023-04-13 16:55:31 +02:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel rcu: Fix missing TICK_DEP_MASK_RCU_EXP dependency check 2023-05-11 23:03:06 +09:00
lib debugobject: Prevent init race with static objects 2023-05-11 23:03:16 +09:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm mm/mempolicy: fix use-after-free of VMA iterator 2023-05-01 08:26:27 +09:00
net bluetooth: Perform careful capability checks in hci_sock_ioctl() 2023-05-01 08:26:27 +09:00
rust rust: kernel: Mark rust_fmt_argument as extern "C" 2023-04-26 14:28:38 +02:00
samples ftrace: Export ftrace_free_filter() to modules 2023-02-01 08:34:37 +01:00
scripts ASN.1: Fix check for strdup() success 2023-04-26 14:28:44 +02:00
security selinux: ensure av_permissions.h is built when needed 2023-05-11 23:03:06 +09:00
sound ASoC: amd: ps: update the acp clock source. 2023-05-11 23:02:59 +09:00
tools tools/x86/kcpuid: Fix avx512bw and avx512lvl fields in Fn00000007 2023-05-11 23:03:07 +09:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt KVM: Register /dev/kvm as the _very_ last thing during initialization 2023-03-10 09:34:11 +01:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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 dts files 2019-12-04 19:44:11 -08:00
.gitignore Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
.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 MAINTAINERS: Remove Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
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 audit: update the mailing list in MAINTAINERS 2023-02-25 11:25:42 +01:00
Makefile Linux 6.1.27 2023-05-01 08:26:28 +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.