user/sven/linux.git/kernel/power/user.c, branch v5.4.249

PM: hibernate: defer device probing when resuming from hibernation

2022-08-25T09:17:32Z

[ Upstream commit 8386c414e27caba8501119948e9551e52b527f59 ] syzbot is reporting hung task at misc_open() [1], for there is a race window of AB-BA deadlock which involves probe_count variable. Currently wait_for_device_probe() from snapshot_open() from misc_open() can sleep forever with misc_mtx held if probe_count cannot become 0. When a device is probed by hub_event() work function, probe_count is incremented before the probe function starts, and probe_count is decremented after the probe function completed. There are three cases that can prevent probe_count from dropping to 0. (a) A device being probed stopped responding (i.e. broken/malicious hardware). (b) A process emulating a USB device using /dev/raw-gadget interface stopped responding for some reason. (c) New device probe requests keeps coming in before existing device probe requests complete. The phenomenon syzbot is reporting is (b). A process which is holding system_transition_mutex and misc_mtx is waiting for probe_count to become 0 inside wait_for_device_probe(), but the probe function which is called from hub_event() work function is waiting for the processes which are blocked at mutex_lock(&misc_mtx) to respond via /dev/raw-gadget interface. This patch mitigates (b) by deferring wait_for_device_probe() from snapshot_open() to snapshot_write() and snapshot_ioctl(). Please note that the possibility of (b) remains as long as any thread which is emulating a USB device via /dev/raw-gadget interface can be blocked by uninterruptible blocking operations (e.g. mutex_lock()). Please also note that (a) and (c) are not addressed. Regarding (c), we should change the code to wait for only one device which contains the image for resuming from hibernation. I don't know how to address (a), for use of timeout for wait_for_device_probe() might result in loss of user data in the image. Maybe we should require the userland to wait for the image device before opening /dev/snapshot interface. Link: https://syzkaller.appspot.com/bug?extid=358c9ab4c93da7b7238c [1] Reported-by: syzbot Signed-off-by: Tetsuo Handa Tested-by: syzbot Signed-off-by: Rafael J. Wysocki Signed-off-by: Sasha Levin

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 428

2019-06-05T15:37:16Z

Based on 1 normalized pattern(s): this file is released under the gplv2 extracted by the scancode license scanner the SPDX license identifier GPL-2.0-only has been chosen to replace the boilerplate/reference in 68 file(s). Signed-off-by: Thomas Gleixner Reviewed-by: Armijn Hemel Reviewed-by: Allison Randal Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190531190114.292346262@linutronix.de Signed-off-by: Greg Kroah-Hartman

PM / sleep: Refactor filesystems sync to reduce duplication

2019-04-02T08:53:19Z

Create a common helper to sync filesystems for system suspend and hibernation. Signed-off-by: Harry Pan Acked-by: Pavel Machek [ rjw: Changelog ] Signed-off-by: Rafael J. Wysocki

PM / reboot: Eliminate race between reboot and suspend

2018-08-06T10:35:20Z

At present, "systemctl suspend" and "shutdown" can run in parrallel. A system can suspend after devices_shutdown(), and resume. Then the shutdown task goes on to power off. This causes many devices are not really shut off. Hence replacing reboot_mutex with system_transition_mutex (renamed from pm_mutex) to achieve the exclusion. The renaming of pm_mutex as system_transition_mutex can be better to reflect the purpose of the mutex. Signed-off-by: Pingfan Liu Acked-by: Pavel Machek Signed-off-by: Rafael J. Wysocki

PM / hibernate: Fix oops at snapshot_write()

2018-05-27T10:00:02Z

syzbot is reporting NULL pointer dereference at snapshot_write() [1]. This is because data->handle is zero-cleared by ioctl(SNAPSHOT_FREE). Fix this by checking data_of(data->handle) != NULL before using it. [1] https://syzkaller.appspot.com/bug?id=828a3c71bd344a6de8b6a31233d51a72099f27fd Signed-off-by: Tetsuo Handa Reported-by: syzbot Signed-off-by: Rafael J. Wysocki

fs: add ksys_sync() helper; remove in-kernel calls to sys_sync()

2018-04-02T18:16:05Z

Using this helper allows us to avoid the in-kernel calls to the sys_sync() syscall. The ksys_ prefix denotes that this function is meant as a drop-in replacement for the syscall. In particular, it uses the same calling convention as sys_sync(). This patch is part of a series which removes in-kernel calls to syscalls. On this basis, the syscall entry path can be streamlined. For details, see http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net Cc: Alexander Viro Signed-off-by: Dominik Brodowski

Replace with globally

2016-12-24T19:46:01Z

This was entirely automated, using the script by Al: PATT='^[[:blank:]]*#[[:blank:]]*include[[:blank:]]*' sed -i -e "s!$PATT!#include !" \ $(git grep -l "$PATT"|grep -v ^include/linux/uaccess.h) to do the replacement at the end of the merge window. Requested-by: Al Viro Signed-off-by: Linus Torvalds

PM / sleep: make PM notifiers called symmetrically

2016-06-27T22:38:55Z

This makes pm notifier PREPARE/POST symmetrical: if PREPARE fails, we will only undo what ever happened on PREPARE. It fixes the unbalanced CPU hotplug enable in CPU PM notifier. Signed-off-by: Lianwei Wang Signed-off-by: Rafael J. Wysocki

PM / hibernate: introduce "nohibernate" boot parameter

2014-06-16T21:29:39Z

To support using kernel features that are not compatible with hibernation, this creates the "nohibernate" kernel boot parameter to disable both hibernation and resume. This allows hibernation support to be a boot-time choice instead of only a compile-time choice. Signed-off-by: Kees Cook Acked-by: Pavel Machek Signed-off-by: Rafael J. Wysocki

Merge branch 'pm-sleep'

2013-11-19T00:07:08Z

* pm-sleep: PM / Hibernate: Do not crash kernel in free_basic_memory_bitmaps()