| From | Greg Kroah-Hartman <> | Subject | [ 066/123] xhci: fix null-pointer dereference when destroying half-built segment rings | Date | Wed, 9 Jan 2013 12:35:05 -0800 |
| |
3.7-stable review patch. If anyone has any objections, please let me know.
------------------
From: Julius Werner <jwerner@chromium.org>
commit 68e5254adb88bede68285f11fb442a4d34fb550c upstream.
xhci_alloc_segments_for_ring() builds a list of xhci_segments and links the tail to head at the end (forming a ring). When it bails out for OOM reasons half-way through, it tries to destroy its half-built list with xhci_free_segments_for_ring(), even though it is not a ring yet. This causes a null-pointer dereference upon hitting the last element.
Furthermore, one of its callers (xhci_ring_alloc()) mistakenly believes the output parameters to be valid upon this kind of OOM failure, and calls xhci_ring_free() on them. Since the (incomplete) list/ring should already be destroyed in that case, this would lead to a use after free.
This patch fixes those issues by having xhci_alloc_segments_for_ring() destroy its half-built, non-circular list manually and destroying the invalid struct xhci_ring in xhci_ring_alloc() with a plain kfree().
This patch should be backported to kernels as old as 2.6.31, that contains the commit 0ebbab37422315a5d0cb29792271085bafdf38c0 "USB: xhci: Ring allocation and initialization."
A separate patch will need to be developed for kernels older than 3.4, since the ring allocation code was refactored in that kernel.
Signed-off-by: Julius Werner <jwerner@chromium.org> Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/usb/host/xhci-mem.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
--- a/drivers/usb/host/xhci-mem.c +++ b/drivers/usb/host/xhci-mem.c @@ -205,7 +205,12 @@ static int xhci_alloc_segments_for_ring( next = xhci_segment_alloc(xhci, cycle_state, flags); if (!next) { - xhci_free_segments_for_ring(xhci, *first); + prev = *first; + while (prev) { + next = prev->next; + xhci_segment_free(xhci, prev); + prev = next; + } return -ENOMEM; } xhci_link_segments(xhci, prev, next, type); @@ -258,7 +263,7 @@ static struct xhci_ring *xhci_ring_alloc return ring; fail: - xhci_ring_free(xhci, ring); + kfree(ring); return NULL; }
|