]> git.karo-electronics.de Git - linux-beck.git/commit
xhci: fix null-pointer dereference when destroying half-built segment rings
authorJulius Werner <jwerner@chromium.org>
Thu, 1 Nov 2012 19:47:59 +0000 (12:47 -0700)
committerSarah Sharp <sarah.a.sharp@linux.intel.com>
Mon, 12 Nov 2012 19:45:29 +0000 (11:45 -0800)
commit68e5254adb88bede68285f11fb442a4d34fb550c
treed76a3eaa20cf10e011e03518477981d0c4ff85af
parent4525c0a10dff7ad3669763c28016c7daffc3900e
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
drivers/usb/host/xhci-mem.c