On 11/18/19 4:43 PM, Benjamin Tissoires wrote:
On Tue, Nov 5, 2019 at 3:18 PM Phong Tran <tranmanphong@xxxxxxxxx> wrote:
syzbot found a problem using of uinit pointer in
lg4ff_set_autocenter_default().
Reported-by: syzbot+1234691fec1b8ceba8b1@xxxxxxxxxxxxxxxxxxxxxxxxx
Tested by syzbot:
https://groups.google.com/d/msg/syzkaller-bugs/ApnMLW6sfKE/Qq0bIHGEAQAJ
This seems weird to me:
the syzbot link above is about `hid_get_drvdata(hid)`, and, as I read
it, the possibility that hid might not have an initialized value.
In the dashboard [1] shows
BUG: KMSAN: uninit-value in dev_get_drvdata include/linux/device.h:1388
[inline]
BUG: KMSAN: uninit-value in hid_get_drvdata include/linux/hid.h:628 [inline]
BUG: KMSAN: uninit-value in lg4ff_set_autocenter_default+0x23a/0xa20
drivers/hid/hid-lg4ff.c:477
base on that I did the initialization the pointer in the patch.
Here you are changing the initialized values of value, entry and
drv_data, all 3 are never used before their first assignment.
I have a feeling this particular syzbot check has already been fixed
upstream by d9d4b1e46d95 "HID: Fix assumption that devices have
inputs".
I think the commit d9d4b1 fixed this report [2] by syzbot.
[1] https://syzkaller.appspot.com/bug?extid=1234691fec1b8ceba8b1
[2] https://syzkaller.appspot.com/bug?extid=403741a091bf41d4ae79
regards,
Phong.
Cheers,
Benjamin
Signed-off-by: Phong Tran <tranmanphong@xxxxxxxxx>
---
drivers/hid/hid-lg4ff.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/hid/hid-lg4ff.c b/drivers/hid/hid-lg4ff.c
index 5e6a0cef2a06..44dfd08b0c32 100644
--- a/drivers/hid/hid-lg4ff.c
+++ b/drivers/hid/hid-lg4ff.c
@@ -468,10 +468,10 @@ static int lg4ff_play(struct input_dev *dev, void *data, struct ff_effect *effec
static void lg4ff_set_autocenter_default(struct input_dev *dev, u16 magnitude)
{
struct hid_device *hid = input_get_drvdata(dev);
- s32 *value;
+ s32 *value = NULL;
u32 expand_a, expand_b;
- struct lg4ff_device_entry *entry;
- struct lg_drv_data *drv_data;
+ struct lg4ff_device_entry *entry = NULL;
+ struct lg_drv_data *drv_data = NULL;
unsigned long flags;
drv_data = hid_get_drvdata(hid);
--
2.20.1
