Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Content-Type: text/plain; charset="UTF-8"
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
MIME-Version: 1.0
From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, "Jia-Ju Bai" <baijiaju1990@gmail.com>,
        "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>
Date:   Sun, 09 Dec 2018 21:50:33 +0000
Message-ID: <lsq.1544392233.143845085@decadent.org.uk>
Subject: [PATCH 3.16 209/328] usb: misc: uss720: Fix two sleep-in-atomic-context
 bugs
In-Reply-To: <lsq.1544392232.713909046@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

3.16.62-rc1 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 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
@@ -392,7 +392,7 @@ 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;
@@ -402,7 +402,7 @@ 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;
 }