[RFC][PATCH v3 00/33] timers: Use timer_shutdown*() before freeing timers

Steven Rostedt
2022-11-04T05:48:57Z

Back in April, I posted an RFC patch set to help mitigate a common issue
where a timer gets armed just before it is freed, and when the timer
goes off, it crashes in the timer code without any evidence of who the
culprit was. I got side tracked and never finished up on that patch set.
Since this type of crash is still our #1 crash we are seeing in the field,
it has become a priority again to finish it.

This is v3 of that patch set. Thomas Gleixner posted an untested version
that makes timer->function NULL as the flag that it is shutdown. I took that
code, tested it (fixed it up), added more comments, and changed the
name to timer_shutdown_sync(). I also converted it to use WARN_ON_ONCE()
instead of just WARN_ON() as Linus asked for.

I then created a trivial coccinelle script to find where del_timer*()
is called before being freed, and converted them all to timer_shutdown*()
(There was a couple that still used del_timer() instead of del_timer_sync()).

I also updated DEBUG_OBJECTS_TIMERS to check from where the timer is ever
armed, to calling of timer_shutdown_sync(), and it will trigger if a timer
is freed in between. The current way is to only check if the timer is armed,
but that means it only triggers if the race condition is hit, and with
experience, it's not run on enough machines to catch all of them. By triggering
it from the time the timer is armed to the time it is shutdown, it catches
all potential cases even if the race condition is not hit.

I went though the result of the cocinelle script, and updated the locations.
Some locations were caught by DEBUG_OBJECTS_TIMERS as the coccinelle script
only checked for timers being freed in the same function as the del_timer*().

Ideally, I would have the first patch go into this rc cycle, which is mostly
non functional as it will allow the other patches to come in via the respective
subsystems in the next merge window.

Changes since v2: https://lore.kernel.org/all/20221027150525.753064657@goodmis.org/

- Talking with Thomas Gleixner, he wanted a better name space and to remove
the "del_" portion of the API.

- Since there's now a shutdown interface that does not synchronize, to keep
it closer to del_timer() and del_timer_sync(), the API is now:

timer_shutdown() - same as del_timer() but deactivates the timer.

timer_shutdown_sync() - same as del_timer_sync() but deactivates the timer.

- Added a few more locations that got converted.

git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
trace/timers

Head SHA1: 25106f0bb7968b3e8c746a7853f44b51840746c3

Steven Rostedt (Google) (33):
timers: Add timer_shutdown_sync() and timer_shutdown() to be called before freeing timers
timers: s390/cmm: Use timer_shutdown_sync() before freeing timer
timers: sh: Use timer_shutdown_sync() before freeing timer
timers: block: Use timer_shutdown_sync() before freeing timer
timers: ACPI: Use timer_shutdown_sync() before freeing timer
timers: atm: Use timer_shutdown_sync() before freeing timer
timers: PM: Use timer_shutdown_sync()
timers: Bluetooth: Use timer_shutdown_sync() before freeing timer
timers: hangcheck: Use timer_shutdown_sync() before freeing timer
timers: ipmi: Use timer_shutdown_sync() before freeing timer
random: use timer_shutdown_sync() before freeing timer
timers: dma-buf: Use timer_shutdown_sync() before freeing timer
timers: drm: Use timer_shutdown_sync() before freeing timer
timers: HID: Use timer_shutdown_sync() before freeing timer
timers: Input: Use timer_shutdown_sync() before freeing timer
timers: mISDN: Use timer_shutdown_sync() before freeing timer
timers: leds: Use timer_shutdown_sync() before freeing timer
timers: media: Use timer_shutdown_sync() before freeing timer
timers: net: Use timer_shutdown_sync() before freeing timer
timers: usb: Use timer_shutdown_sync() before freeing timer
timers: cgroup: Use timer_shutdown_sync() before freeing timer
timers: workqueue: Use timer_shutdown_sync() before freeing timer
timers: nfc: pn533: Use timer_shutdown_sync() before freeing timer
timers: pcmcia: Use timer_shutdown_sync() before freeing timer
timers: scsi: Use timer_shutdown_sync() and timer_shutdown() before freeing timer
timers: tty: Use timer_shutdown_sync() before freeing timer
timers: ext4: Use timer_shutdown_sync() before freeing timer
timers: fs/nilfs2: Use timer_shutdown_sync() before freeing timer
timers: ALSA: Use timer_shutdown_sync() before freeing timer
timers: jbd2: Use timer_shutdown() before freeing timer
timers: sched/psi: Use timer_shutdown_sync() before freeing timer
timers: x86/mce: Use __init_timer() for resetting timers
timers: Expand DEBUG_OBJECTS_TIMER to check if it ever was used

----
.../RCU/Design/Requirements/Requirements.rst | 2 +-
Documentation/core-api/local_ops.rst | 2 +-
Documentation/kernel-hacking/locking.rst | 5 +
arch/s390/mm/cmm.c | 4 +-
arch/sh/drivers/push-switch.c | 2 +-
arch/x86/kernel/cpu/mce/core.c | 14 ++-
block/blk-iocost.c | 2 +-
block/blk-iolatency.c | 2 +-
block/blk-stat.c | 2 +-
block/blk-throttle.c | 2 +-
block/kyber-iosched.c | 2 +-
drivers/acpi/apei/ghes.c | 2 +-
drivers/atm/idt77105.c | 4 +-
drivers/atm/idt77252.c | 4 +-
drivers/atm/iphase.c | 2 +-
drivers/base/power/wakeup.c | 7 +-
drivers/block/drbd/drbd_main.c | 2 +-
drivers/block/loop.c | 2 +-
drivers/block/sunvdc.c | 2 +-
drivers/bluetooth/hci_bcsp.c | 2 +-
drivers/bluetooth/hci_h5.c | 2 +-
drivers/bluetooth/hci_qca.c | 4 +-
drivers/char/hangcheck-timer.c | 4 +-
drivers/char/ipmi/ipmi_msghandler.c | 2 +-
drivers/char/ipmi/ipmi_ssif.c | 4 +-
drivers/char/random.c | 2 +-
drivers/dma-buf/st-dma-fence.c | 2 +-
drivers/gpu/drm/gud/gud_pipe.c | 2 +-
drivers/gpu/drm/i915/i915_sw_fence.c | 2 +-
drivers/hid/hid-wiimote-core.c | 2 +-
drivers/input/keyboard/locomokbd.c | 2 +-
drivers/input/keyboard/omap-keypad.c | 2 +-
drivers/input/mouse/alps.c | 2 +-
drivers/input/serio/hil_mlc.c | 2 +-
drivers/input/serio/hp_sdc.c | 2 +-
drivers/isdn/hardware/mISDN/hfcmulti.c | 6 +-
drivers/isdn/mISDN/l1oip_core.c | 4 +-
drivers/isdn/mISDN/timerdev.c | 4 +-
drivers/leds/trigger/ledtrig-activity.c | 2 +-
drivers/leds/trigger/ledtrig-heartbeat.c | 2 +-
drivers/leds/trigger/ledtrig-pattern.c | 2 +-
drivers/leds/trigger/ledtrig-transient.c | 2 +-
drivers/media/pci/ivtv/ivtv-driver.c | 2 +-
drivers/media/usb/pvrusb2/pvrusb2-hdw.c | 18 ++--
drivers/media/usb/s2255/s2255drv.c | 4 +-
drivers/net/ethernet/intel/i40e/i40e_main.c | 6 +-
drivers/net/ethernet/marvell/sky2.c | 2 +-
drivers/net/ethernet/sun/sunvnet.c | 2 +-
drivers/net/usb/sierra_net.c | 2 +-
drivers/net/wireless/intel/iwlwifi/iwl-dbg-tlv.c | 2 +-
drivers/net/wireless/intersil/hostap/hostap_ap.c | 2 +-
drivers/net/wireless/marvell/mwifiex/main.c | 2 +-
drivers/net/wireless/microchip/wilc1000/hif.c | 8 +-
drivers/nfc/pn533/pn533.c | 2 +-
drivers/nfc/pn533/uart.c | 2 +-
drivers/pcmcia/bcm63xx_pcmcia.c | 2 +-
drivers/pcmcia/electra_cf.c | 2 +-
drivers/pcmcia/omap_cf.c | 2 +-
drivers/pcmcia/pd6729.c | 4 +-
drivers/pcmcia/yenta_socket.c | 4 +-
drivers/scsi/qla2xxx/qla_edif.c | 4 +-
drivers/scsi/scsi_lib.c | 1 +
drivers/staging/media/atomisp/i2c/atomisp-lm3554.c | 2 +-
drivers/tty/n_gsm.c | 2 +-
drivers/tty/sysrq.c | 2 +-
drivers/usb/gadget/udc/m66592-udc.c | 2 +-
drivers/usb/serial/garmin_gps.c | 2 +-
drivers/usb/serial/mos7840.c | 2 +-
fs/ext4/super.c | 2 +-
fs/jbd2/journal.c | 2 +
fs/nilfs2/segment.c | 2 +-
include/linux/timer.h | 100 +++++++++++++++++--
include/linux/workqueue.h | 4 +-
kernel/cgroup/cgroup.c | 2 +-
kernel/sched/psi.c | 1 +
kernel/time/timer.c | 106 ++++++++++++++-------
kernel/workqueue.c | 4 +-
net/802/garp.c | 2 +-
net/802/mrp.c | 2 +-
net/bridge/br_multicast.c | 6 +-
net/bridge/br_multicast_eht.c | 4 +-
net/core/gen_estimator.c | 2 +-
net/core/neighbour.c | 2 +
net/ipv4/inet_connection_sock.c | 2 +-
net/ipv4/inet_timewait_sock.c | 3 +-
net/ipv4/ipmr.c | 2 +-
net/ipv6/ip6mr.c | 2 +-
net/mac80211/mesh_pathtbl.c | 2 +-
net/netfilter/ipset/ip_set_list_set.c | 2 +-
net/netfilter/ipvs/ip_vs_lblc.c | 2 +-
net/netfilter/ipvs/ip_vs_lblcr.c | 2 +-
net/netfilter/xt_LED.c | 2 +-
net/rxrpc/conn_object.c | 2 +-
net/sched/cls_flow.c | 2 +-
net/sunrpc/svc.c | 2 +-
net/sunrpc/xprt.c | 2 +-
net/tipc/discover.c | 2 +-
net/tipc/monitor.c | 2 +-
sound/i2c/other/ak4117.c | 2 +-
sound/synth/emux/emux.c | 2 +-
100 files changed, 310 insertions(+), 175 deletions(-)