This is a note to let you know that I've just added the patch titled
USB: cdc-acm: fix write and resume race
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
usb-cdc-acm-fix-write-and-resume-race.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From e144ed28bed10684f9aaec6325ed974d53f76110 Mon Sep 17 00:00:00 2001
From: Johan Hovold <[email protected]>
Date: Mon, 26 May 2014 19:23:37 +0200
Subject: USB: cdc-acm: fix write and resume race
From: Johan Hovold <[email protected]>
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 <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
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
@@ -1468,27 +1468,20 @@ 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);
}
/*
@@ -1496,12 +1489,14 @@ 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;
}
Patches currently in stable-queue which might be from [email protected] are
queue-3.4/usb-cdc-acm-fix-i-o-after-failed-open.patch
queue-3.4/usb-cdc-acm-fix-write-and-resume-race.patch
queue-3.4/usb-cdc-acm-fix-runtime-pm-for-control-messages.patch
queue-3.4/usb-cdc-acm-fix-broken-runtime-suspend.patch
queue-3.4/usb-cdc-acm-fix-runtime-pm-imbalance-at-shutdown.patch
queue-3.4/usb-cdc-acm-fix-shutdown-and-suspend-race.patch
queue-3.4/usb-cdc-acm-fix-write-and-suspend-race.patch
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