USB: cdc-acm: fix write and resume race (e144ed28) · Commits · 戴 / test

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: ("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>

drivers/usb/class/cdc-acm.c

+9 −14

Original line number	Diff line number	Diff line
		@@ -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;
		}

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