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

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 3.2: 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>
This commit is contained in:
Mathias Nyman 2017-12-08 18:10:05 +02:00 committed by syphyr
parent 3ad6671dd5
commit 060e0ded6f
1 changed files with 13 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
drivers/usb/host/xhci-mem.c
View File

@ -996,10 +996,9 @@ 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);
@ -1048,9 +1047,19 @@ int xhci_alloc_virt_device(struct xhci_hcd *xhci, int slot_id,
&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;
}