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media: bt878: do not schedule tasklet when it is not setup

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There is a problem with the tasklet in bt878. bt->tasklet is set by
dvb-bt8xx.ko, and bt878.ko can be loaded independently.
In this case if interrupt comes it may cause null-ptr-dereference.
To solve this issue, we check if the tasklet is actually set before
calling tasklet_schedule.

[    1.750438] bt878(0): irq FDSR FBUS risc_pc=
[    1.750728] BUG: kernel NULL pointer dereference, address: 0000000000000000
[    1.752969] RIP: 0010:0x0
[    1.757526] Call Trace:
[    1.757659]  <IRQ>
[    1.757770]  tasklet_action_common.isra.0+0x107/0x110
[    1.758041]  tasklet_action+0x22/0x30
[    1.758237]  __do_softirq+0xe0/0x29b
[    1.758430]  irq_exit_rcu+0xa4/0xb0
[    1.758618]  common_interrupt+0x8d/0xa0
[    1.758824]  </IRQ>

Signed-off-by: Tong Zhang <ztong0001@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
This commit is contained in:
Tong Zhang 2021-04-29 00:12:26 +02:00 committed by Mauro Carvalho Chehab
parent 14480e8df8
commit a3a54bf4bd
1 changed files with 2 additions and 1 deletions
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3
drivers/media/pci/bt8xx/bt878.c
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@ -300,7 +300,8 @@ static irqreturn_t bt878_irq(int irq, void *dev_id)
}
if (astat & BT878_ARISCI) {
bt->finished_block = (stat & BT878_ARISCS) >> 28;
tasklet_schedule(&bt->tasklet);
if (bt->tasklet.callback)
tasklet_schedule(&bt->tasklet);
break;
}
count++;