Messages in this thread Patch in this message | | | From | Guenter Roeck <> | Subject | [RFC PATCH] xhci: Fix memory use after free in xhci_free_virt_device | Date | Tue, 15 Nov 2016 12:36:39 -0800 |
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The following use-after-free reports were seen on resume with a specific USB hub.
BUG: KASAN: use-after-free in xhci_free_virt_device+0x8c/0x21c at addr ffffffc0cc1a2eb0 BUG: KASAN: use-after-free in xhci_update_tt_active_eps+0x9c/0xdc at addr ffffffc0cc1a2eb0
Relevant traceback for the first case is:
xhci_free_virt_device+0x8c/0x21c xhci_mem_cleanup+0x294/0x81c xhci_resume+0x410/0x618 xhci_plat_resume+0x54/0x74 platform_pm_resume+0x74/0x84
which points to the following code in xhci_free_virt_device().
if (dev->tt_info) old_active_eps = dev->tt_info->active_eps;
Problem with this code is that xhci_mem_cleanup() cleans up devices starting with slot 1, and dev->tt_info for a device with higher slot number can point back to the tt_info associated with device 1. In lsusb, this looks as follows.
/: Bus 05.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 480M |__ Port 1: Dev 4, If 0, Class=Hub, Driver=hub/4p, 480M |__ Port 3: Dev 7, If 0, Class=Vendor Specific Class, Driver=, 12M
When the higher-numbered device is cleared, it tries to access the already released tt_info from slot 1 to get the value of old_active_eps.
The problem is not seen with all USB hubs since not all USB hubs require the cleanup handling in xhci_resume().
Signed-off-by: Guenter Roeck <linux@roeck-us.net> --- Marked as RFC because I don't really like this fix at all and would prefer a different solution.
It might be possible, for example, to change the code in xhci_mem_cleanup() from for (i = 1; i < MAX_HC_SLOTS; ++i) xhci_free_virt_device(xhci, i); to for (i = MAX_HC_SLOTS - 1; i >= 1; i--) xhci_free_virt_device(xhci, i); if it is guaranteed that tt_info never points to a device with higher slot number.
drivers/usb/host/xhci-mem.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c index 6afe32381209..97a61c57a2ed 100644 --- a/drivers/usb/host/xhci-mem.c +++ b/drivers/usb/host/xhci-mem.c @@ -873,8 +873,14 @@ static void xhci_free_tt_info(struct xhci_hcd *xhci, list_for_each_entry_safe(tt_info, next, tt_list_head, tt_list) { /* Multi-TT hubs will have more than one entry */ if (tt_info->slot_id == slot_id) { + int i; + slot_found = true; list_del(&tt_info->tt_list); + for (i = 0; i < MAX_HC_SLOTS; i++) + if (xhci->devs[i] && + xhci->devs[i]->tt_info == tt_info) + xhci->devs[i]->tt_info = NULL; kfree(tt_info); } else if (slot_found) { break; -- 2.5.0
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