From c69b8186945c10d245586e9f9703486e9574170c Mon Sep 17 00:00:00 2001 From: Andrzej Pietrasiewicz Date: Tue, 3 Mar 2015 10:52:07 +0100 Subject: [PATCH] usb: gadget: printer: eliminate random pointer dereference struct printer_dev contains 3 list heads: tx_reqs, rx_reqs and rx_buffers. There is just one instance of this structure in the driver and it is file static, and as such initialized with all zeros. If device_create() or cdev_add() fails then "goto fail" branch is taken, which results in printer_cfg_unbind() call. The latter checks if tx_reqs, rx_reqs and rx_buffers lists are empty. The check for emptiness is in fact a check whether the "next" member of struct list_head points to the head of the list. But the heads of the lists in question have not been initialized yet and, as mentioned above, contain all zeros, so list_empty() returns false and respective "while" loop body starts executing. Here, container_of() just subtracts the offset of a struct usb_request member from an address of this same member, which results in a value somewhere near 0 or 0xfff...ff. And the argument to list_del() dereferences such a pointer which causes a disaster. This patch moves respective INIT_LIST_HEAD() invocations to a point before "goto fail" branch can be taken. Signed-off-by: Andrzej Pietrasiewicz Signed-off-by: Felipe Balbi --- drivers/usb/gadget/legacy/printer.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/usb/gadget/legacy/printer.c b/drivers/usb/gadget/legacy/printer.c index 21ea317d2a43..12247d3fe768 100644 --- a/drivers/usb/gadget/legacy/printer.c +++ b/drivers/usb/gadget/legacy/printer.c @@ -1190,6 +1190,9 @@ static int __init printer_bind_config(struct usb_configuration *c) dev->function.unbind = printer_func_unbind; dev->function.set_alt = printer_func_set_alt; dev->function.disable = printer_func_disable; + INIT_LIST_HEAD(&dev->tx_reqs); + INIT_LIST_HEAD(&dev->rx_reqs); + INIT_LIST_HEAD(&dev->rx_buffers); status = usb_add_function(c, &dev->function); if (status) @@ -1233,11 +1236,8 @@ static int __init printer_bind_config(struct usb_configuration *c) spin_lock_init(&dev->lock); mutex_init(&dev->lock_printer_io); - INIT_LIST_HEAD(&dev->tx_reqs); INIT_LIST_HEAD(&dev->tx_reqs_active); - INIT_LIST_HEAD(&dev->rx_reqs); INIT_LIST_HEAD(&dev->rx_reqs_active); - INIT_LIST_HEAD(&dev->rx_buffers); init_waitqueue_head(&dev->rx_wait); init_waitqueue_head(&dev->tx_wait); init_waitqueue_head(&dev->tx_flush_wait); -- 2.20.1