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Revision 6941051d3028963c3b0b3fcdd0815f2b51b957bb authored by Sudeep Holla on 18 October 2019, 10:58:15 UTC, committed by Rafael J. Wysocki on 22 October 2019, 16:07:30 UTC 
cpufreq: Cancel policy update work scheduled before freeing
 
Scheduled policy update work may end up racing with the freeing of the
policy and unregistering the driver.

One possible race is as below, where the cpufreq_driver is unregistered,
but the scheduled work gets executed at later stage when, cpufreq_driver
is NULL (i.e. after freeing the policy and driver).

Unable to handle kernel NULL pointer dereference at virtual address 0000001c
pgd = (ptrval)
[0000001c] *pgd=80000080204003, *pmd=00000000
Internal error: Oops: 206 [#1] SMP THUMB2
Modules linked in:
CPU: 0 PID: 34 Comm: kworker/0:1 Not tainted 5.4.0-rc3-00006-g67f5a8081a4b #86
Hardware name: ARM-Versatile Express
Workqueue: events handle_update
PC is at cpufreq_set_policy+0x58/0x228
LR is at dev_pm_qos_read_value+0x77/0xac
Control: 70c5387d  Table: 80203000  DAC: fffffffd
Process kworker/0:1 (pid: 34, stack limit = 0x(ptrval))
	(cpufreq_set_policy) from (refresh_frequency_limits.part.24+0x37/0x48)
	(refresh_frequency_limits.part.24) from (handle_update+0x2f/0x38)
	(handle_update) from (process_one_work+0x16d/0x3cc)
	(process_one_work) from (worker_thread+0xff/0x414)
	(worker_thread) from (kthread+0xff/0x100)
	(kthread) from (ret_from_fork+0x11/0x28)

Fixes: 67d874c3b2c6 ("cpufreq: Register notifiers with the PM QoS framework")
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
[ rjw: Cancel the work before dropping the QoS requests ]
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
1 parent 2aac8bd
Raw File
Kbuild 
# SPDX-License-Identifier: GPL-2.0
#
# Kbuild for top-level directory of the kernel

#####
# Generate bounds.h

bounds-file := include/generated/bounds.h

always  := $(bounds-file)
targets := kernel/bounds.s

$(bounds-file): kernel/bounds.s FORCE
	$(call filechk,offsets,__LINUX_BOUNDS_H__)

#####
# Generate timeconst.h

timeconst-file := include/generated/timeconst.h

filechk_gentimeconst = echo $(CONFIG_HZ) | bc -q $<

$(timeconst-file): kernel/time/timeconst.bc FORCE
	$(call filechk,gentimeconst)

#####
# Generate asm-offsets.h

offsets-file := include/generated/asm-offsets.h

always  += $(offsets-file)
targets += arch/$(SRCARCH)/kernel/asm-offsets.s

arch/$(SRCARCH)/kernel/asm-offsets.s: $(timeconst-file) $(bounds-file)

$(offsets-file): arch/$(SRCARCH)/kernel/asm-offsets.s FORCE
	$(call filechk,offsets,__ASM_OFFSETS_H__)

#####
# Check for missing system calls

always += missing-syscalls

quiet_cmd_syscalls = CALL    $<
      cmd_syscalls = $(CONFIG_SHELL) $< $(CC) $(c_flags) $(missing_syscalls_flags)

missing-syscalls: scripts/checksyscalls.sh $(offsets-file) FORCE
	$(call cmd,syscalls)

#####
# Check atomic headers are up-to-date

always += old-atomics

quiet_cmd_atomics = CALL    $<
      cmd_atomics = $(CONFIG_SHELL) $<

old-atomics: scripts/atomic/check-atomics.sh FORCE
	$(call cmd,atomics)
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