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USB: cdc-acm: fix write and resume race 

Fix race between write() and resume() due to improper locking that could
lead to writes being reordered.

Resume must be done atomically and susp_count be protected by the
write_lock in order to prevent racing with write(). This could otherwise
lead to writes being reordered if write() grabs the write_lock after
susp_count is decremented, but before the delayed urb is submitted.

Fixes: 11ea859d64 ("USB: additional power savings for cdc-acm devices
that support remote wakeup")

Cc: <stable@vger.kernel.org>	# v2.6.27
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Johan Hovold 2014-05-26 19:23:37 +02:00 committed by Greg Kroah-Hartman
parent 5a345c20c1
commit e144ed28be
1 changed files with 9 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
drivers/usb/class/cdc-acm.c
View File

@ -1541,27 +1541,20 @@ static int acm_resume(struct usb_interface *intf)
struct acm *acm = usb_get_intfdata(intf);
struct acm_wb *wb;
int rv = 0;
int cnt;
spin_lock_irq(&acm->read_lock);
acm->susp_count -= 1;
cnt = acm->susp_count;
spin_unlock_irq(&acm->read_lock);
spin_lock(&acm->write_lock);
if (cnt)
return 0;
if (--acm->susp_count)
goto out;
if (test_bit(ASYNCB_INITIALIZED, &acm->port.flags)) {
rv = usb_submit_urb(acm->ctrlurb, GFP_NOIO);
rv = usb_submit_urb(acm->ctrlurb, GFP_ATOMIC);
spin_lock_irq(&acm->write_lock);
if (acm->delayed_wb) {
wb = acm->delayed_wb;
acm->delayed_wb = NULL;
spin_unlock_irq(&acm->write_lock);
acm_start_wb(acm, wb);
} else {
spin_unlock_irq(&acm->write_lock);
}
/*
@ -1569,12 +1562,14 @@ static int acm_resume(struct usb_interface *intf)
* do the write path at all cost
*/
if (rv < 0)
goto err_out;
goto out;
rv = acm_submit_read_urbs(acm, GFP_NOIO);
rv = acm_submit_read_urbs(acm, GFP_ATOMIC);
}
out:
spin_unlock(&acm->write_lock);
spin_unlock_irq(&acm->read_lock);
err_out:
return rv;
}