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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jia-Ju Bai <baijiaju1990@gmail.com>
Subject: [PATCH 4.9 064/111] usb: misc: uss720: Fix two sleep-in-atomic-context bugs
Date:   Mon, 24 Sep 2018 13:52:31 +0200
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jia-Ju Bai <baijiaju1990@gmail.com>

commit bc8acc214d3f1cafebcbcd101a695bbac716595d upstream.

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@gmail.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/usb/misc/uss720.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/usb/misc/uss720.c
+++ b/drivers/usb/misc/uss720.c
@@ -385,7 +385,7 @@ static unsigned char parport_uss720_frob
 	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;
@@ -395,7 +395,7 @@ static unsigned char parport_uss720_read
 {
 	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;
 }