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| author | Ethan Zhao <ethan.zhao@oracle.com> | 2014-12-18 07:28:19 +0100 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2014-12-19 22:49:07 +0100 |
| commit | cb57720bf79688d64854a0a43565aa52303c1f3f (patch) | |
| tree | ad0465a343069351a26fc43fb8759fe5254229b4 /arch/m68k | |
| parent | cpufreq-dt: defer probing if OPP table is not ready (diff) | |
| download | linux-cb57720bf79688d64854a0a43565aa52303c1f3f.tar.xz linux-cb57720bf79688d64854a0a43565aa52303c1f3f.zip | |
cpufreq: fix a NULL pointer dereference in __cpufreq_governor()
If ACPI _PPC changed notification happens before governor was initiated
while kernel is booting, a NULL pointer dereference will be triggered:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000030
IP: [<ffffffff81470453>] __cpufreq_governor+0x23/0x1e0
PGD 0
Oops: 0000 [#1] SMP
... ...
RIP: 0010:[<ffffffff81470453>] [<ffffffff81470453>]
__cpufreq_governor+0x23/0x1e0
RSP: 0018:ffff881fcfbcfbb8 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffff881fd11b3980 RCX: ffff88407fc20000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff881fd11b3980
RBP: ffff881fcfbcfbd8 R08: 0000000000000000 R09: 000000000000000f
R10: ffffffff818068d0 R11: 0000000000000043 R12: 0000000000000004
R13: 0000000000000000 R14: ffffffff8196cae0 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff881fffc00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000030 CR3: 00000000018ae000 CR4: 00000000000407f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process kworker/0:3 (pid: 750, threadinfo ffff881fcfbce000, task
ffff881fcf556400)
Stack:
ffff881fffc17d00 ffff881fcfbcfc18 ffff881fd11b3980 0000000000000000
ffff881fcfbcfc08 ffffffff81470d08 ffff881fd11b3980 0000000000000007
ffff881fcfbcfc18 ffff881fffc17d00 ffff881fcfbcfd28 ffffffff81472e9a
Call Trace:
[<ffffffff81470d08>] __cpufreq_set_policy+0x1b8/0x2e0
[<ffffffff81472e9a>] cpufreq_update_policy+0xca/0x150
[<ffffffff81472f20>] ? cpufreq_update_policy+0x150/0x150
[<ffffffff81324a96>] acpi_processor_ppc_has_changed+0x71/0x7b
[<ffffffff81320bcd>] acpi_processor_notify+0x55/0x115
[<ffffffff812f9c29>] acpi_device_notify+0x19/0x1b
[<ffffffff813084ca>] acpi_ev_notify_dispatch+0x41/0x5f
[<ffffffff812f64a4>] acpi_os_execute_deferred+0x27/0x34
The root cause is a race conditon -- cpufreq core and acpi-cpufreq driver
were initiated, but cpufreq_governor wasn't and _PPC changed notification
happened, __cpufreq_governor() was called within acpi_os_execute_deferred
kernel thread context.
To fix this panic issue, add pointer checking code in __cpufreq_governor()
before pointer policy->governor is to be dereferenced.
Signed-off-by: Ethan Zhao <ethan.zhao@oracle.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'arch/m68k')
0 files changed, 0 insertions, 0 deletions