Hi all,
getting a tpriv->urbs NULL pointer causes negative urb_idx and successively an
undefined behavior! This happens when removing a USB device during a transfer
with a chance of ~ 20%.
With the small extension the error can be made visible:
static int handle_bulk_completion(struct usbi_transfer *itransfer,
struct usbfs_urb *urb)
{
struct linux_transfer_priv *tpriv =
usbi_transfer_get_os_priv(itransfer);
struct libusb_transfer *transfer =
USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
int urb_idx = urb - tpriv->urbs;
usbi_mutex_lock(&itransfer->lock);
usbi_dbg("handling completion status %d of bulk urb %d/%d", urb->status,
urb_idx + 1, tpriv->num_urbs);
+ if (urb_idx < -2)
+ {
+ usbi_dbg("usb_idx lt 0: %d %p %p
%d",urb_idx,urb,tpriv->urbs,tpriv->num_urbs);
+ }
example result:
Nov 14 00:15:31 (none) daemon.debug my_prog: [ 6.744000] [00007c5b] libusbx:
debug [usbi_handle_transfer_completion] transfer 0x880b114 has callback
0xb7045e40
Nov 14 00:15:31 (none) daemon.debug my_prog: [ 6.744000] [00007c5b] libusbx:
debug [sync_transfer_cb] actual_length=0
Nov 14 00:15:31 (none) daemon.debug my_prog: [ 6.744000] [00007c5b] libusbx:
debug [reap_for_handle] urb type=3 status=-2 transferred=0
Nov 14 00:15:31 (none) daemon.debug my_prog: [ 6.744000] [00007c5b] libusbx:
debug [handle_bulk_completion] handling completion status -2 of bulk urb
-1168226879/4
Nov 14 00:15:31 (none) daemon.debug my_prog: [ 6.744000] [00007c5b] libusbx:
debug [handle_bulk_completion] usb_idx lt 0: -1168226880 0x833fd00 (nil) 4
Nov 14 00:15:31 (none) daemon.debug my_prog: [ 6.774000] [00007c51] libusbx:
debug [linux_netlink_read_message] netlink hotplug found device busnum: 2,
devaddr: 77, sys_name: 2-1.4, removed: yes
It looks like an inconsistency between the tpriv->urbs pointer and
tpriv->num_urbs. If there are no URBs (null pointer) but the number of urbs is >
0 there is an inconsistency appearing somewhere...
Best regards,
Erik
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