linux-kernel - [PATCH 2/3] cdc-acm: call usb_autopm_get_interface_upgrade in, acm_tty

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Date:	Tue, 26 May 2015 10:20:22 +0800
From:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	xinhuix.pan@...el.com,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alan Cox <alan@...ux.intel.com>
Subject: [PATCH 2/3] cdc-acm: call usb_autopm_get_interface_upgrade in, acm_tty_write

acm device might be used as ldisc device by n_gsm driver.

gsmtty_write and other gsm functions calls acm_tty_write

indirectly while they holds spinlocks.

Meanwhile, application might access ACM tty device directly.

Here we choose to call usb_autopm_get_interface_upgrade instead of

usb_autopm_get_interface_async to make sure above 2 scenarios can

work well.

Signed-off-by: Zhang Yanmin <yanmin.zhang@...el.com>

---

---
  drivers/usb/class/cdc-acm.c | 13 ++++++-------
  1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 5c8f581..6ad85a3 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -689,10 +689,15 @@ static int acm_tty_write(struct tty_struct *tty,
  
  	dev_vdbg(&acm->data->dev, "%s - count %d\n", __func__, count);
  
+	stat = usb_autopm_get_interface_upgrade(acm->control);
+	if (stat)
+		return stat;
+
  	spin_lock_irqsave(&acm->write_lock, flags);
  	wbn = acm_wb_alloc(acm);
  	if (wbn < 0) {
  		spin_unlock_irqrestore(&acm->write_lock, flags);
+		usb_autopm_put_interface(acm->control);
  		return 0;
  	}
  	wb = &acm->wb[wbn];
@@ -700,6 +705,7 @@ static int acm_tty_write(struct tty_struct *tty,
  	if (!acm->dev) {
  		wb->use = 0;
  		spin_unlock_irqrestore(&acm->write_lock, flags);
+		usb_autopm_put_interface(acm->control);
  		return -ENODEV;
  	}
  
@@ -708,13 +714,6 @@ static int acm_tty_write(struct tty_struct *tty,
  	memcpy(wb->buf, buf, count);
  	wb->len = count;
  
-	stat = usb_autopm_get_interface_async(acm->control);
-	if (stat) {
-		wb->use = 0;
-		spin_unlock_irqrestore(&acm->write_lock, flags);
-		return stat;
-	}
-
  	if (acm->susp_count) {
  		usb_anchor_urb(wb->urb, &acm->delayed);
  		spin_unlock_irqrestore(&acm->write_lock, flags);
-- 
1.9.1


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