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authorJulius Werner <jwerner@chromium.org>2012-11-01 12:47:59 -0700
committerSarah Sharp <sarah.a.sharp@linux.intel.com>2012-11-12 11:45:29 -0800
commit68e5254adb88bede68285f11fb442a4d34fb550c (patch)
treed76a3eaa20cf10e011e03518477981d0c4ff85af /drivers
parent4525c0a10dff7ad3669763c28016c7daffc3900e (diff)
xhci: fix null-pointer dereference when destroying half-built segment rings
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> Cc: stable@vger.kernel.org
Diffstat (limited to 'drivers')
-rw-r--r--drivers/usb/host/xhci-mem.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index 487bc083dead..fb51c7085ad0 100644
--- 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(struct xhci_hcd *xhci,
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(struct xhci_hcd *xhci,
return ring;
fail:
- xhci_ring_free(xhci, ring);
+ kfree(ring);
return NULL;
}