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xhci: Don't add a virt_dev to the devs array before it's fully allocated 

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."

Cc: stable <stable@vger.kernel.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Mathias Nyman 2017-12-08 18:10:05 +02:00 committed by Greg Kroah-Hartman
parent be6123df1e
commit 5d9b70f7d5
1 changed files with 11 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
drivers/usb/host/xhci-mem.c
View File

@ -971,10 +971,9 @@ int xhci_alloc_virt_device(struct xhci_hcd *xhci, int slot_id,
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);
@ -1015,9 +1014,17 @@ int xhci_alloc_virt_device(struct xhci_hcd *xhci, int slot_id,
trace_xhci_alloc_virt_device(dev);
xhci->devs[slot_id] = dev;
return 1;
fail:
xhci_free_virt_device(xhci, slot_id);
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;
}