[34-longterm 211/247] USB: cdc-acm: fix potential null-pointer dereference on disconnect

From: Paul Gortmaker
Date: Thu Jun 23 2011 - 13:51:17 EST

From: Johan Hovold <jhovold@xxxxxxxxx>

This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.

commit 7e7797e7f6f7bfab73fca02c65e40eaa5bb9000c upstream.

Fix potential null-pointer exception on disconnect introduced by commit
11ea859d64b69a747d6b060b9ed1520eab1161fe (USB: additional power savings
for cdc-acm devices that support remote wakeup).

Only access acm->dev after making sure it is non-null in control urb
completion handler.

Signed-off-by: Johan Hovold <jhovold@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
drivers/usb/class/cdc-acm.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index a45e6c4..073a9ef 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -297,6 +297,8 @@ static void acm_ctrl_irq(struct urb *urb)
if (!ACM_READY(acm))
goto exit;

+ usb_mark_last_busy(acm->dev);
data = (unsigned char *)(dr + 1);
switch (dr->bNotificationType) {
@@ -336,7 +338,6 @@ static void acm_ctrl_irq(struct urb *urb)
- usb_mark_last_busy(acm->dev);
retval = usb_submit_urb(urb, GFP_ATOMIC);
if (retval)
dev_err(&urb->dev->dev, "%s - usb_submit_urb failed with "

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/