[PATCH] usb: misc: uss720: Fix two sleep-in-atomic-context bugs

[Jia-Ju Bai]

async_complete() in uss720.c is a completion handler function for the 
USB driver. So it should not sleep, but it is can sleep according to the
function call paths (from bottom to top) in Linux-4.16.

[FUNC] set_1284_register(GFP_KERNEL)
drivers/usb/misc/uss720.c, 372:
  set_1284_register in parport_uss720_frob_control
drivers/parport/ieee1284.c, 560:
  [FUNC_PTR]parport_uss720_frob_control in parport_ieee1284_ack_data_avail
drivers/parport/ieee1284.c, 577:
  parport_ieee1284_ack_data_avail in parport_ieee1284_interrupt
./include/linux/parport.h, 474:
  parport_ieee1284_interrupt in parport_generic_irq
drivers/usb/misc/uss720.c, 116:
  parport_generic_irq in async_complete

[FUNC] get_1284_register(GFP_KERNEL)
drivers/usb/misc/uss720.c, 382: 
  get_1284_register in parport_uss720_read_status
drivers/parport/ieee1284.c, 555: 
  [FUNC_PTR]parport_uss720_read_status in parport_ieee1284_ack_data_avail
drivers/parport/ieee1284.c, 577: 
  parport_ieee1284_ack_data_avail in parport_ieee1284_interrupt
./include/linux/parport.h, 474: 
  parport_ieee1284_interrupt in parport_generic_irq
drivers/usb/misc/uss720.c, 116: 
  parport_generic_irq in async_complete

Note that [FUNC_PTR] means a function pointer call is used.

To fix these bugs, GFP_KERNEL is replaced with GFP_ATOMIC.

These bugs are found by my static analysis tool DSAC.

Signed-off-by: Jia-Ju Bai <baijiaju1990@xxxxxxxxx>
---
 drivers/usb/misc/uss720.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/misc/uss720.c b/drivers/usb/misc/uss720.c
index de9a502491c2..69822852888a 100644
--- a/drivers/usb/misc/uss720.c
+++ b/drivers/usb/misc/uss720.c
@@ -369,7 +369,7 @@ static unsigned char parport_uss720_frob_control(struct parport *pp, unsigned ch
 	mask &= 0x0f;
 	val &= 0x0f;
 	d = (priv->reg[1] & (~mask)) ^ val;
-	if (set_1284_register(pp, 2, d, GFP_KERNEL))
+	if (set_1284_register(pp, 2, d, GFP_ATOMIC))
 		return 0;
 	priv->reg[1] = d;
 	return d & 0xf;
@@ -379,7 +379,7 @@ static unsigned char parport_uss720_read_status(struct parport *pp)
 {
 	unsigned char ret;
 
-	if (get_1284_register(pp, 1, &ret, GFP_KERNEL))
+	if (get_1284_register(pp, 1, &ret, GFP_ATOMIC))
 		return 0;
 	return ret & 0xf8;
 }
-- 
2.17.0