3.16.55-rc1 review patch. If anyone has any objections, please let me know.
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From: Mathias Nyman mathias.nyman@linux.intel.com
commit 5d9b70f7d52eb14bb37861c663bae44de9521c35 upstream.
Avoid null pointer dereference if some function is walking through the devs array accessing members of a new virt_dev that is mid allocation.
Add the virt_dev to xhci->devs[i] _after_ the virt_device and all its members are properly allocated.
issue found by KASAN: null-ptr-deref in xhci_find_slot_id_by_port
"Quick analysis suggests that xhci_alloc_virt_device() is not mutex protected. If so, there is a time frame where xhci->devs[slot_id] is set but not fully initialized. Specifically, xhci->devs[i]->udev can be NULL."
Signed-off-by: Mathias Nyman mathias.nyman@linux.intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org [bwh: Backported to 3.16: There is an extra failure path, so we may need to free dev->eps[0].ring] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- --- a/drivers/usb/host/xhci-mem.c +++ b/drivers/usb/host/xhci-mem.c @@ -1018,10 +1018,9 @@ int xhci_alloc_virt_device(struct xhci_h return 0; }
- xhci->devs[slot_id] = kzalloc(sizeof(*xhci->devs[slot_id]), flags); - if (!xhci->devs[slot_id]) + dev = kzalloc(sizeof(*dev), flags); + if (!dev) return 0; - dev = xhci->devs[slot_id];
/* Allocate the (output) device context that will be used in the HC. */ dev->out_ctx = xhci_alloc_container_ctx(xhci, XHCI_CTX_TYPE_DEVICE, flags); @@ -1069,9 +1068,19 @@ int xhci_alloc_virt_device(struct xhci_h &xhci->dcbaa->dev_context_ptrs[slot_id], le64_to_cpu(xhci->dcbaa->dev_context_ptrs[slot_id]));
+ xhci->devs[slot_id] = dev; + return 1; fail: - xhci_free_virt_device(xhci, slot_id); + + if (dev->eps[0].ring) + xhci_ring_free(xhci, dev->eps[0].ring); + if (dev->in_ctx) + xhci_free_container_ctx(xhci, dev->in_ctx); + if (dev->out_ctx) + xhci_free_container_ctx(xhci, dev->out_ctx); + kfree(dev); + return 0; }