In the Linux kernel, the following vulnerability has been resolved:
fuse-uring: make a fuse_req on SQE commit only findable after memcpy
Bad userspace might try to trick us and send commit SQEs request
unique / commit-id of requests that are not even send to
fuse-server (io_uring_cmd_done() not called) yet.
fuse_uring_commit_fetch() ends the fuse request when the ring entry
has a wrong state, but that could have caused a use-after-free
with the memcpy operations in fuse_uring_send_in_task().
In order to avoid such races the call of fuse_uring_add_to_pq()
is moved after the copy operations and just before completing
the io-uring request - malicious userspace cannot find the request
anymore until all prepration work in fuse-client/kernel is completed.
This also moves fuse_uring_add_to_pq() a bit up in the code to
avoid a forward declaration. Also not with a preparation commit,
to make it easier to back port to older kernels.