In the Linux kernel, the following vulnerability has been resolved:
cuse: wait for pending RCU callbacks on module exit
Since commit 053fc4f755ad ("fuse: fix UAF in rcu pathwalks"),
fuse_conn_put() frees the fuse_conn through call_rcu() rather than
synchronously. For cuse, fc->release is cuse_fc_release(), which
lives in the cuse module. If the module is removed before the RCU
grace period ends, the callback jumps into freed module memory:
userspace / module unload | RCU softirq
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
close(/dev/cuse) |
cuse_channel_release() |
fuse_dev_release() |
fuse_conn_put(fch->conn) |
call_rcu(delayed_release) ------+---> callback queued
|
rmmod cuse |
cuse_exit() |
cuse_channel_destroy() |
... |
return |
|
Unknown