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usb: require FMODE_WRITE for usbdev_mmap()

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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: Jann Horn <jannh@google.com>
Link: https://lore.kernel.org/r/20241016-usbdev-mmap-require-write-v1-1-6f8256414d5c@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jann Horn 2024-10-16 17:24:06 +02:00 committed by Greg Kroah-Hartman
parent 7b5a58952f
commit 3ea36dc8dd
1 changed files with 3 additions and 0 deletions
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3
drivers/usb/core/devio.c
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@ -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;