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 <li...@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
