This is a note to let you know that I've just added the patch titled
cdc-wdm: Fix more races on the read path
to the 3.3-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:
cdc-wdm-fix-more-races-on-the-read-path.patch
and it can be found in the queue-3.3 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 711c68b3c0f7a924ffbee4aa962d8f62b85188ff Mon Sep 17 00:00:00 2001
From: Ben Hutchings <[email protected]>
Date: Sun, 12 Feb 2012 06:00:41 +0000
Subject: cdc-wdm: Fix more races on the read path
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
From: Ben Hutchings <[email protected]>
commit 711c68b3c0f7a924ffbee4aa962d8f62b85188ff upstream.
We must not allow the input buffer length to change while we're
shuffling the buffer contents. We also mustn't clear the WDM_READ
flag after more data might have arrived. Therefore move both of these
into the spinlocked region at the bottom of wdm_read().
When reading desc->length without holding the iuspin lock, use
ACCESS_ONCE() to ensure the compiler doesn't re-read it with
inconsistent results.
Signed-off-by: Ben Hutchings <[email protected]>
Tested-by: Bjørn Mork <[email protected]>
Cc: Oliver Neukum <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/usb/class/cdc-wdm.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -397,7 +397,7 @@ outnl:
static ssize_t wdm_read
(struct file *file, char __user *buffer, size_t count, loff_t *ppos)
{
- int rv, cntr = 0;
+ int rv, cntr;
int i = 0;
struct wdm_device *desc = file->private_data;
@@ -406,7 +406,8 @@ static ssize_t wdm_read
if (rv < 0)
return -ERESTARTSYS;
- if (desc->length == 0) {
+ cntr = ACCESS_ONCE(desc->length);
+ if (cntr == 0) {
desc->read = 0;
retry:
if (test_bit(WDM_DISCONNECTING, &desc->flags)) {
@@ -457,25 +458,30 @@ retry:
goto retry;
}
clear_bit(WDM_READ, &desc->flags);
+ cntr = desc->length;
spin_unlock_irq(&desc->iuspin);
}
- cntr = count > desc->length ? desc->length : count;
+ if (cntr > count)
+ cntr = count;
rv = copy_to_user(buffer, desc->ubuf, cntr);
if (rv > 0) {
rv = -EFAULT;
goto err;
}
+ spin_lock_irq(&desc->iuspin);
+
for (i = 0; i < desc->length - cntr; i++)
desc->ubuf[i] = desc->ubuf[i + cntr];
- spin_lock_irq(&desc->iuspin);
desc->length -= cntr;
- spin_unlock_irq(&desc->iuspin);
/* in case we had outstanding data */
if (!desc->length)
clear_bit(WDM_READ, &desc->flags);
+
+ spin_unlock_irq(&desc->iuspin);
+
rv = cntr;
err:
Patches currently in stable-queue which might be from [email protected] are
queue-3.3/cdc-wdm-fix-more-races-on-the-read-path.patch
queue-3.3/cdc-wdm-don-t-clear-wdm_read-unless-entire-read-buffer-is-emptied.patch
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
