Comments
Patch
@@ -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;
}
This is a note to let you know that I have just added a patch titled xhci: fix null-pointer dereference when destroying to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.5.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Herton ------ From 3f18ab73cef1a8756eeee55507ed1a0610157670 Mon Sep 17 00:00:00 2001 From: Julius Werner <jwerner@chromium.org> Date: Thu, 1 Nov 2012 12:47:59 -0700 Subject: [PATCH] xhci: fix null-pointer dereference when destroying half-built segment rings 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: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com> --- drivers/usb/host/xhci-mem.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) -- 1.7.9.5