| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.10 30/52] USB: cdc-acm: fix write and suspend race | Date | Tue, 24 Jun 2014 11:50:45 -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 5a345c20c17d87099224a4be12e69e5bd7023dca upstream.
Fix race between write() and suspend() which could lead to writes being dropped (or I/O while suspended) if the device is runtime suspended while a write request is being processed.
Specifically, suspend() releases the write_lock after determining the device is idle but before incrementing the susp_count, thus leaving a window where a concurrent write() can submit an urb.
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 | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-)
--- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -1434,18 +1434,15 @@ static int acm_suspend(struct usb_interf struct acm *acm = usb_get_intfdata(intf); int cnt; + spin_lock_irq(&acm->read_lock); + spin_lock(&acm->write_lock); if (PMSG_IS_AUTO(message)) { - int b; - - spin_lock_irq(&acm->write_lock); - b = acm->transmitting; - spin_unlock_irq(&acm->write_lock); - if (b) + if (acm->transmitting) { + spin_unlock(&acm->write_lock); + spin_unlock_irq(&acm->read_lock); return -EBUSY; + } } - - spin_lock_irq(&acm->read_lock); - spin_lock(&acm->write_lock); cnt = acm->susp_count++; spin_unlock(&acm->write_lock); spin_unlock_irq(&acm->read_lock);
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