usb: xhci: Bugfix for NULL pointer deference in xhci_endpoint_init() function
virt_dev->num_cached_rings counts on freed ring and is not updated correctly. In xhci_free_or_cache_endpoint_ring() function, the free ring is added into cache and then num_rings_cache is incremented as below: virt_dev->ring_cache[rings_cached] = virt_dev->eps[ep_index].ring; virt_dev->num_rings_cached++; here, free ring pointer is added to a current index and then index is incremented. So current index always points to empty location in the ring cache. For getting available free ring, current index should be decremented first and then corresponding ring buffer value should be taken from ring cache. But In function xhci_endpoint_init(), the num_rings_cached index is accessed before decrement. virt_dev->eps[ep_index].new_ring = virt_dev->ring_cache[virt_dev->num_rings_cached]; virt_dev->ring_cache[virt_dev->num_rings_cached] = NULL; virt_dev->num_rings_cached--; This is bug in manipulating the index of ring cache. And it should be as below: virt_dev->num_rings_cached--; virt_dev->eps[ep_index].new_ring = virt_dev->ring_cache[virt_dev->num_rings_cached]; virt_dev->ring_cache[virt_dev->num_rings_cached] = NULL; Cc: <stable@vger.kernel.org> Signed-off-by: Aman Deep <aman.deep@samsung.com> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -1427,10 +1427,10 @@ int xhci_endpoint_init(struct xhci_hcd *xhci,
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/* Attempt to use the ring cache */
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if (virt_dev->num_rings_cached == 0)
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return -ENOMEM;
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virt_dev->num_rings_cached--;
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virt_dev->eps[ep_index].new_ring =
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virt_dev->ring_cache[virt_dev->num_rings_cached];
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virt_dev->ring_cache[virt_dev->num_rings_cached] = NULL;
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virt_dev->num_rings_cached--;
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xhci_reinit_cached_ring(xhci, virt_dev->eps[ep_index].new_ring,
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1, type);
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}
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