The syzbot fuzzer found a race between URB submission to endpoint 0
and device reset. Namely, during the reset we call usb_ep0_reinit()
because the characteristics of ep0 may have changed (if the reset
follows a firmware update, for example). While usb_ep0_reinit() is
running there is a brief period during which the pointers stored in
udev->ep_in[0] and udev->ep_out[0] are set to NULL, and if an URB is
submitted to ep0 during that period, usb_urb_ep_type_check() will
report it as a driver bug. In the absence of those pointers, the
routine thinks that the endpoint doesn't exist. The log message looks
like this:
------------[ cut here ]------------
usb 2-1: BOGUS urb xfer, pipe 2 != type 2
WARNING: CPU: 0 PID: 9241 at drivers/usb/core/urb.c:478
usb_submit_urb+0x1188/0x1460 drivers/usb/core/urb.c:478
Now, although submitting an URB while the device is being reset is a
questionable thing to do, it shouldn't count as a driver bug as severe
as submitting an URB for an endpoint that doesn't exist. Indeed,
endpoint 0 always exists, even while the device is in its unconfigured
state.
To prevent these misleading driver bug reports, this patch updates
usb_disable_endpoint() to avoid clearing the ep_in[] and ep_out[]
pointers when the endpoint being disabled is ep0. There's no danger
of leaving a stale pointer in place, because the usb_host_endpoint
structure being pointed to is stored permanently in udev->ep0; it
doesn't get deallocated until the entire usb_device structure does.
Reported-and-tested-by: syzbot+db339689b2101f6f6071@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
---
I don't think this needs to go into the stable kernels. It only avoids
a dev_WARN() call, and the problem only occurs under fairly unlikely
circumstances.
[as1938]
drivers/usb/core/message.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
Index: usb-devel/drivers/usb/core/message.c
===================================================================
--- usb-devel.orig/drivers/usb/core/message.c
+++ usb-devel/drivers/usb/core/message.c
@@ -1143,11 +1143,11 @@ void usb_disable_endpoint(struct usb_dev
if (usb_endpoint_out(epaddr)) {
ep = dev->ep_out[epnum];
- if (reset_hardware)
+ if (reset_hardware && epnum != 0)
dev->ep_out[epnum] = NULL;
} else {
ep = dev->ep_in[epnum];
- if (reset_hardware)
+ if (reset_hardware && epnum != 0)
dev->ep_in[epnum] = NULL;
}
if (ep) {
