diff options
author | Julius Werner <jwerner@chromium.org> | 2012-11-01 23:47:59 +0400 |
---|---|---|
committer | Sarah Sharp <sarah.a.sharp@linux.intel.com> | 2012-11-12 23:45:29 +0400 |
commit | 68e5254adb88bede68285f11fb442a4d34fb550c (patch) | |
tree | d76a3eaa20cf10e011e03518477981d0c4ff85af /drivers/usb | |
parent | 4525c0a10dff7ad3669763c28016c7daffc3900e (diff) | |
download | linux-68e5254adb88bede68285f11fb442a4d34fb550c.tar.xz |
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/usb')
-rw-r--r-- | drivers/usb/host/xhci-mem.c | 9 |
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; } |