From 656eca37aae1f7dad26693ab1bd1c1d4f110741c Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Wed, 22 Jun 2022 10:46:31 -0400 Subject: [PATCH] USB: gadget: Fix double-free bug in raw_gadget driver commit 90bc2af24638659da56397ff835f3c95a948f991 upstream. Re-reading a recently merged fix to the raw_gadget driver showed that it inadvertently introduced a double-free bug in a failure pathway. If raw_ioctl_init() encounters an error after the driver ID number has been allocated, it deallocates the ID number before returning. But when dev_free() runs later on, it will then try to deallocate the ID number a second time. Closely related to this issue is another error in the recent fix: The ID number is stored in the raw_dev structure before the code checks to see whether the structure has already been initialized, in which case the new ID number would overwrite the earlier value. The solution to both bugs is to keep the new ID number in a local variable, and store it in the raw_dev structure only after the check for prior initialization. No errors can occur after that point, so the double-free will never happen. Fixes: f2d8c2606825 ("usb: gadget: Fix non-unique driver names in raw-gadget driver") CC: Andrey Konovalov CC: Signed-off-by: Alan Stern Link: https://lore.kernel.org/r/YrMrRw5AyIZghN0v@rowland.harvard.edu Signed-off-by: Greg Kroah-Hartman --- drivers/usb/gadget/legacy/raw_gadget.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/drivers/usb/gadget/legacy/raw_gadget.c b/drivers/usb/gadget/legacy/raw_gadget.c index a8154813af58..b496ca937dee 100644 --- a/drivers/usb/gadget/legacy/raw_gadget.c +++ b/drivers/usb/gadget/legacy/raw_gadget.c @@ -429,6 +429,7 @@ static int raw_release(struct inode *inode, struct file *fd) static int raw_ioctl_init(struct raw_dev *dev, unsigned long value) { int ret = 0; + int driver_id_number; struct usb_raw_init arg; char *udc_driver_name; char *udc_device_name; @@ -451,10 +452,9 @@ static int raw_ioctl_init(struct raw_dev *dev, unsigned long value) return -EINVAL; } - ret = ida_alloc(&driver_id_numbers, GFP_KERNEL); - if (ret < 0) - return ret; - dev->driver_id_number = ret; + driver_id_number = ida_alloc(&driver_id_numbers, GFP_KERNEL); + if (driver_id_number < 0) + return driver_id_number; driver_driver_name = kmalloc(DRIVER_DRIVER_NAME_LENGTH_MAX, GFP_KERNEL); if (!driver_driver_name) { @@ -462,7 +462,7 @@ static int raw_ioctl_init(struct raw_dev *dev, unsigned long value) goto out_free_driver_id_number; } snprintf(driver_driver_name, DRIVER_DRIVER_NAME_LENGTH_MAX, - DRIVER_NAME ".%d", dev->driver_id_number); + DRIVER_NAME ".%d", driver_id_number); udc_driver_name = kmalloc(UDC_NAME_LENGTH_MAX, GFP_KERNEL); if (!udc_driver_name) { @@ -506,6 +506,7 @@ static int raw_ioctl_init(struct raw_dev *dev, unsigned long value) dev->driver.driver.name = driver_driver_name; dev->driver.udc_name = udc_device_name; dev->driver.match_existing_only = 1; + dev->driver_id_number = driver_id_number; dev->state = STATE_DEV_INITIALIZED; spin_unlock_irqrestore(&dev->lock, flags); @@ -520,7 +521,7 @@ static int raw_ioctl_init(struct raw_dev *dev, unsigned long value) out_free_driver_driver_name: kfree(driver_driver_name); out_free_driver_id_number: - ida_free(&driver_id_numbers, dev->driver_id_number); + ida_free(&driver_id_numbers, driver_id_number); return ret; }