* [PATCH 1/2] USB: ldusb: fix read info leaks
2019-10-18 14:17 [PATCH 0/2] USB: ldusb: fix ring-buffer bugs Johan Hovold
@ 2019-10-18 14:17 ` Johan Hovold
2019-10-18 15:03 ` Johan Hovold
2019-10-18 14:17 ` [PATCH RFC 2/2] USB: ldusb: fix ring-buffer locking Johan Hovold
1 sibling, 1 reply; 4+ messages in thread
From: Johan Hovold @ 2019-10-18 14:17 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: Alan Stern, Oliver Neukum, Paul E . McKenney, linux-usb,
linux-kernel, Johan Hovold, stable, syzbot+6fe95b826644f7f12b0b
Fix broken read implementation, which could be used to trigger slab info
leaks.
The driver failed to check if the custom ring buffer was still empty
when waking up after having waited for more data. This would happen on
every interrupt-in completion, even if no data had been added to the
ring buffer (e.g. on disconnect events).
Due to missing sanity checks and uninitialised (kmalloced) ring-buffer
entries, this meant that huge slab info leaks could easily be triggered.
Note that the empty-buffer check after wakeup is enough to fix the info
leak on disconnect, but let's clear the buffer on allocation and add a
sanity check to read() to prevent further leaks.
Fixes: 2824bd250f0b ("[PATCH] USB: add ldusb driver")
Cc: stable <stable@vger.kernel.org> # 2.6.13
Reported-by: syzbot+6fe95b826644f7f12b0b@syzkaller.appspotmail.com
Signed-off-by: Johan Hovold <johan@kernel.org>
---
drivers/usb/misc/ldusb.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)
diff --git a/drivers/usb/misc/ldusb.c b/drivers/usb/misc/ldusb.c
index 147c90c2a4e5..94780e14e95d 100644
--- a/drivers/usb/misc/ldusb.c
+++ b/drivers/usb/misc/ldusb.c
@@ -464,7 +464,7 @@ static ssize_t ld_usb_read(struct file *file, char __user *buffer, size_t count,
/* wait for data */
spin_lock_irq(&dev->rbsl);
- if (dev->ring_head == dev->ring_tail) {
+ while (dev->ring_head == dev->ring_tail) {
dev->interrupt_in_done = 0;
spin_unlock_irq(&dev->rbsl);
if (file->f_flags & O_NONBLOCK) {
@@ -474,12 +474,17 @@ static ssize_t ld_usb_read(struct file *file, char __user *buffer, size_t count,
retval = wait_event_interruptible(dev->read_wait, dev->interrupt_in_done);
if (retval < 0)
goto unlock_exit;
- } else {
- spin_unlock_irq(&dev->rbsl);
+
+ spin_lock_irq(&dev->rbsl);
}
+ spin_unlock_irq(&dev->rbsl);
/* actual_buffer contains actual_length + interrupt_in_buffer */
actual_buffer = (size_t *)(dev->ring_buffer + dev->ring_tail * (sizeof(size_t)+dev->interrupt_in_endpoint_size));
+ if (*actual_buffer > sizeof(size_t) + dev->interrupt_in_endpoint_size) {
+ retval = -EIO;
+ goto unlock_exit;
+ }
bytes_to_read = min(count, *actual_buffer);
if (bytes_to_read < *actual_buffer)
dev_warn(&dev->intf->dev, "Read buffer overflow, %zd bytes dropped\n",
@@ -690,10 +695,9 @@ static int ld_usb_probe(struct usb_interface *intf, const struct usb_device_id *
dev_warn(&intf->dev, "Interrupt out endpoint not found (using control endpoint instead)\n");
dev->interrupt_in_endpoint_size = usb_endpoint_maxp(dev->interrupt_in_endpoint);
- dev->ring_buffer =
- kmalloc_array(ring_buffer_size,
- sizeof(size_t) + dev->interrupt_in_endpoint_size,
- GFP_KERNEL);
+ dev->ring_buffer = kcalloc(ring_buffer_size,
+ sizeof(size_t) + dev->interrupt_in_endpoint_size,
+ GFP_KERNEL);
if (!dev->ring_buffer)
goto error;
dev->interrupt_in_buffer = kmalloc(dev->interrupt_in_endpoint_size, GFP_KERNEL);
--
2.23.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH RFC 2/2] USB: ldusb: fix ring-buffer locking
2019-10-18 14:17 [PATCH 0/2] USB: ldusb: fix ring-buffer bugs Johan Hovold
2019-10-18 14:17 ` [PATCH 1/2] USB: ldusb: fix read info leaks Johan Hovold
@ 2019-10-18 14:17 ` Johan Hovold
1 sibling, 0 replies; 4+ messages in thread
From: Johan Hovold @ 2019-10-18 14:17 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: Alan Stern, Oliver Neukum, Paul E . McKenney, linux-usb,
linux-kernel, Johan Hovold, stable
The custom ring-buffer implementation was merged without any locking
whatsoever, but a spinlock was later added by commit 9d33efd9a791
("USB: ldusb bugfix").
The lock did not cover the loads from the ring-buffer-entry after
determining the buffer was non-empty, nor the update of the tail index
once the entry had been processed. The former could lead to stale data
being returned, while the latter could lead to memory corruption on
sufficiently weakly ordered architectures.
Fixes: 2824bd250f0b ("[PATCH] USB: add ldusb driver")
Fixes: 9d33efd9a791 ("USB: ldusb bugfix")
Cc: stable <stable@vger.kernel.org> # 2.6.13
Signed-off-by: Johan Hovold <johan@kernel.org>
---
drivers/usb/misc/ldusb.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/misc/ldusb.c b/drivers/usb/misc/ldusb.c
index 94780e14e95d..c6cf2fa6cf4c 100644
--- a/drivers/usb/misc/ldusb.c
+++ b/drivers/usb/misc/ldusb.c
@@ -477,11 +477,11 @@ static ssize_t ld_usb_read(struct file *file, char __user *buffer, size_t count,
spin_lock_irq(&dev->rbsl);
}
- spin_unlock_irq(&dev->rbsl);
/* actual_buffer contains actual_length + interrupt_in_buffer */
actual_buffer = (size_t *)(dev->ring_buffer + dev->ring_tail * (sizeof(size_t)+dev->interrupt_in_endpoint_size));
if (*actual_buffer > sizeof(size_t) + dev->interrupt_in_endpoint_size) {
+ spin_unlock_irq(&dev->rbsl);
retval = -EIO;
goto unlock_exit;
}
@@ -489,17 +489,26 @@ static ssize_t ld_usb_read(struct file *file, char __user *buffer, size_t count,
if (bytes_to_read < *actual_buffer)
dev_warn(&dev->intf->dev, "Read buffer overflow, %zd bytes dropped\n",
*actual_buffer-bytes_to_read);
+ spin_unlock_irq(&dev->rbsl);
+
+ /*
+ * Pairs with spin_unlock_irqrestore() in
+ * ld_usb_interrupt_in_callback() and makes sure the ring-buffer entry
+ * has been updated before copy_to_user().
+ */
+ smp_rmb();
/* copy one interrupt_in_buffer from ring_buffer into userspace */
if (copy_to_user(buffer, actual_buffer+1, bytes_to_read)) {
retval = -EFAULT;
goto unlock_exit;
}
- dev->ring_tail = (dev->ring_tail+1) % ring_buffer_size;
-
retval = bytes_to_read;
spin_lock_irq(&dev->rbsl);
+
+ dev->ring_tail = (dev->ring_tail + 1) % ring_buffer_size;
+
if (dev->buffer_overflow) {
dev->buffer_overflow = 0;
spin_unlock_irq(&dev->rbsl);
--
2.23.0
^ permalink raw reply related [flat|nested] 4+ messages in thread