In the Linux kernel, the following vulnerability has been resolved:
misc: nsm: pin the module while the device is open
misc_open() installs a misc driver’s file operations with fops_get(),
which pins file_operations::owner before replacing the file’s f_op. The
NSM misc device leaves nsm_dev_fops.owner unset, so opening /dev/nsm does
not take a module reference on the nsm driver.
If the driver is built as a module, an open file descriptor can therefore
survive rmmod of the module that provides its ioctl callbacks. A later
ioctl through that descriptor can call into unloaded module text.
Set nsm_dev_fops.owner to THIS_MODULE so the misc core holds the module
while any /dev/nsm file descriptor is open, matching the lifetime
expectation for the installed file operations.
