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| author | Alan Stern <stern@rowland.harvard.edu> | 2012-09-26 13:09:53 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-09-26 10:21:08 -0700 |
| commit | 0a2314035cab62cafc38ea11ec5b6f95cf347b38 (patch) | |
| tree | 6b06f4fe9e60ee8590fdd4b0a516fe0c56e37c0f | |
| parent | 655db7980596f0ad4f15f8f4c51beb3e705762de (diff) | |
| download | linux-0a2314035cab62cafc38ea11ec5b6f95cf347b38.tar.gz linux-0a2314035cab62cafc38ea11ec5b6f95cf347b38.tar.bz2 linux-0a2314035cab62cafc38ea11ec5b6f95cf347b38.zip | |
USB: Fix race condition when removing host controllers
This patch (as1607) fixes a race that can occur if a USB host
controller is removed while a process is reading the
/sys/kernel/debug/usb/devices file.
The usb_device_read() routine uses the bus->root_hub pointer to
determine whether or not the root hub is registered. The is not a
valid test, because the pointer is set before the root hub gets
registered and remains set even after the root hub is unregistered and
deallocated. As a result, usb_device_read() or usb_device_dump() can
access freed memory, causing an oops.
The patch changes the test to use the hcd->rh_registered flag, which
does get set and cleared at the appropriate times. It also makes sure
to hold the usb_bus_list_lock mutex while setting the flag, so that
usb_device_read() will become aware of new root hubs as soon as they
are registered.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Don Zickus <dzickus@redhat.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/usb/core/devices.c | 2 | ||||
| -rw-r--r-- | drivers/usb/core/hcd.c | 6 |
2 files changed, 3 insertions, 5 deletions
diff --git a/drivers/usb/core/devices.c b/drivers/usb/core/devices.c index f4ead1296820..f460de31acee 100644 --- a/drivers/usb/core/devices.c +++ b/drivers/usb/core/devices.c @@ -623,7 +623,7 @@ static ssize_t usb_device_read(struct file *file, char __user *buf, /* print devices for all busses */ list_for_each_entry(bus, &usb_bus_list, bus_list) { /* recurse through all children of the root hub */ - if (!bus->root_hub) + if (!bus_to_hcd(bus)->rh_registered) continue; usb_lock_device(bus->root_hub); ret = usb_device_dump(&buf, &nbytes, &skip_bytes, ppos, diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c index 35b52f6e1c5e..1e741bca0265 100644 --- a/drivers/usb/core/hcd.c +++ b/drivers/usb/core/hcd.c @@ -1011,10 +1011,7 @@ static int register_root_hub(struct usb_hcd *hcd) if (retval) { dev_err (parent_dev, "can't register root hub for %s, %d\n", dev_name(&usb_dev->dev), retval); - } - mutex_unlock(&usb_bus_list_lock); - - if (retval == 0) { + } else { spin_lock_irq (&hcd_root_hub_lock); hcd->rh_registered = 1; spin_unlock_irq (&hcd_root_hub_lock); @@ -1023,6 +1020,7 @@ static int register_root_hub(struct usb_hcd *hcd) if (HCD_DEAD(hcd)) usb_hc_died (hcd); /* This time clean up */ } + mutex_unlock(&usb_bus_list_lock); return retval; } |