3.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Johan Hovold <jhovold@xxxxxxxxx>
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@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -1441,18 +1441,15 @@ 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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