This is a note to let you know that I've just added the patch titled
media: bt878: do not schedule tasklet when it is not setup
to the 5.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
media-bt878-do-not-schedule-tasklet-when-it-is-not-s.patch
and it can be found in the queue-5.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 5dcd4b2c0b7303854e84b894c2c745bc3d39a355
Author: Tong Zhang <ztong0001@xxxxxxxxx>
Date: Thu Apr 29 00:12:26 2021 +0200
media: bt878: do not schedule tasklet when it is not setup
[ Upstream commit a3a54bf4bddaecda8b5767209cfc703f0be2841d ]
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@xxxxxxxxx>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/media/pci/bt8xx/bt878.c b/drivers/media/pci/bt8xx/bt878.c
index 78dd35c9b65d..7ca309121fb5 100644
--- a/drivers/media/pci/bt8xx/bt878.c
+++ b/drivers/media/pci/bt8xx/bt878.c
@@ -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++;
