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Tetsuo Handa 4cf6ba9367 media: imon: reorganize serialization 
[ Upstream commit db264d4c66 ]

Since usb_register_dev() from imon_init_display() from imon_probe() holds
minor_rwsem while display_open() which holds driver_lock and ictx->lock is
called with minor_rwsem held from usb_open(), holding driver_lock or
ictx->lock when calling usb_register_dev() causes circular locking
dependency problem.

Since usb_deregister_dev() from imon_disconnect() holds minor_rwsem while
display_open() which holds driver_lock is called with minor_rwsem held,
holding driver_lock when calling usb_deregister_dev() also causes circular
locking dependency problem.

Sean Young explained that the problem is there are imon devices which have
two usb interfaces, even though it is one device. The probe and disconnect
function of both usb interfaces can run concurrently.

Alan Stern responded that the driver and USB cores guarantee that when an
interface is probed, both the interface and its USB device are locked.
Ditto for when the disconnect callback gets run. So concurrent probing/
disconnection of multiple interfaces on the same device is not possible.

Therefore, we don't need locks for handling race between imon_probe() and
imon_disconnect(). But we still need to handle race between display_open()
/vfd_write()/lcd_write()/display_close() and imon_disconnect(), for
disconnect event can happen while file descriptors are in use.

Since "struct file"->private_data is set by display_open(), vfd_write()/
lcd_write()/display_close() can assume that "struct file"->private_data
is not NULL even after usb_set_intfdata(interface, NULL) was called.

Replace insufficiently held driver_lock with refcount_t based management.
Add a boolean flag for recording whether imon_disconnect() was already
called. Use RCU for accessing this boolean flag and refcount_t.

Since the boolean flag for imon_disconnect() is shared, disconnect event
on either intf0 or intf1 affects both interfaces. But I assume that this
change does not matter, for usually disconnect event would not happen
while interfaces are in use.

Link: https://syzkaller.appspot.com/bug?extid=c558267ad910fc494497

Reported-by: syzbot <syzbot+c558267ad910fc494497@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Tested-by: syzbot <syzbot+c558267ad910fc494497@syzkaller.appspotmail.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-06-09 10:20:55 +02:00
arch perf/amd/ibs: Cascade pmu init functions' return value 2022-06-09 10:20:54 +02:00
block block-map: add __GFP_ZERO flag for alloc_page in function bio_copy_kern 2022-05-12 12:25:45 +02:00
certs certs: Trigger creation of RSA module signing key if it's not an RSA key 2021-09-15 09:50:29 +02:00
crypto crypto: ecrdsa - Fix incorrect use of vli_cmp 2022-06-06 08:42:43 +02:00
Documentation docs: submitting-patches: Fix crossref to 'The canonical patch format' 2022-06-06 08:42:44 +02:00
drivers media: imon: reorganize serialization 2022-06-09 10:20:55 +02:00
fs btrfs: repair super block num_devices automatically 2022-06-09 10:20:49 +02:00
include ALSA: jack: Access input_dev under mutex 2022-06-09 10:20:51 +02:00
init random: handle latent entropy and command line from random_init() 2022-05-30 09:33:44 +02:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-12-01 09:19:10 +01:00
kernel dma-debug: change allocation mode from GFP_NOWAIT to GFP_ATIOMIC 2022-06-09 10:20:54 +02:00
lib lib/crypto: add prompts back to crypto libraries 2022-06-06 08:42:42 +02:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm zsmalloc: fix races between asynchronous zspage free and page migration 2022-06-06 08:42:43 +02:00
net net: remove two BUG() from skb_checksum_help() 2022-06-09 10:20:54 +02:00
samples samples/bpf, xdpsock: Fix race when running for fix duration of time 2022-04-08 14:40:21 +02:00
scripts gcc-plugins: latent_entropy: use /dev/urandom 2022-04-20 09:23:26 +02:00
security lockdown: also lock down previous kgdb use 2022-05-30 09:33:22 +02:00
sound ASoC: tscs454: Add endianness flag in snd_soc_component_driver 2022-06-09 10:20:54 +02:00
tools tools/power turbostat: fix ICX DRAM power numbers 2022-06-09 10:20:51 +02:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:25:48 +01:00
virt KVM: Prevent module exit until all VMs are freed 2022-04-08 14:40:38 +02:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore kbuild: generate Module.symvers only when vmlinux exists 2021-05-19 10:12:59 +02:00
.mailmap mailmap: add two more addresses of Uwe Kleine-König 2020-12-06 10:19:07 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Jason Cooper to CREDITS 2020-11-30 10:20:34 +01:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: add git tree for random.c 2022-05-30 09:33:24 +02:00
Makefile Linux 5.10.120 2022-06-06 08:42:45 +02:00
README

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.