Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 3.10 31/52] USB: cdc-acm: fix write and resume race | Date | Tue, 24 Jun 2014 11:50:46 -0400 |
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3.10-stable review patch. If anyone has any objections, please let me know.
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From: Johan Hovold <jhovold@gmail.com>
commit e144ed28bed10684f9aaec6325ed974d53f76110 upstream.
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: 11ea859d64b6 ("USB: additional power savings for cdc-acm devices that support remote wakeup")
Signed-off-by: Johan Hovold <jhovold@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/usb/class/cdc-acm.c | 23 +++++++++-------------- 1 file changed, 9 insertions(+), 14 deletions(-)
--- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -1461,27 +1461,20 @@ static int acm_resume(struct usb_interfa 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); } /* @@ -1489,12 +1482,14 @@ static int acm_resume(struct usb_interfa * 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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