Commit 3ea36dc8 authored by Jann Horn's avatar Jann Horn Committed by Greg Kroah-Hartman
Browse files

usb: require FMODE_WRITE for usbdev_mmap() 



usbdev_mmap() creates VMAs which can only be used through
usbdev_do_ioctl(), which requires FMODE_WRITE; so usbdev_mmap() is only
useful with FMODE_WRITE.

On typical Linux systems, files at /dev/bus/usb/*/* are mode 0664, so
UIDs without any special privileges can't use usbdev_do_ioctl(), but
they can still execute the usbdev_mmap() codepath.

Check for FMODE_WRITE in usbdev_mmap() to reduce attack surface a little
bit.

Signed-off-by: default avatarJann Horn <jannh@google.com>
Link: https://lore.kernel.org/r/20241016-usbdev-mmap-require-write-v1-1-6f8256414d5c@google.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 7b5a5895

drivers/usb/core/devio.c

+3 −0
Original line number Diff line number Diff line
@@ -238,6 +238,9 @@ static int usbdev_mmap(struct file *file, struct vm_area_struct *vma) 
	dma_addr_t dma_handle = DMA_MAPPING_ERROR;

	int ret;



	if (!(file->f_mode & FMODE_WRITE))

		return -EPERM;



	ret = usbfs_increase_memory_usage(size + sizeof(struct usb_memory));

	if (ret)

		goto error;