In the Linux kernel, the following vulnerability has been resolved:
dmaengine: idxd: fix double free of wq, engine, and group structs
The release callbacks for wq, engine, and group devices
(idxd_conf_wq_release, idxd_conf_engine_release,
idxd_conf_group_release) each call kfree() on the enclosing struct.
The setup error paths and cleanup functions also call kfree()
explicitly after put_device(), producing a double free whenever
put_device() drops the reference count to zero and fires the release.
In the setup functions, device_initialize() is called before
device_add(), so the reference count is exactly 1 at the error sites.
put_device() unconditionally fires the release, which frees the struct;
the subsequent explicit kfree() then operates on freed memory.
For idxd_setup_wqs(), the wq release callback also owns opcap_bmap
and wqcfg. The error unwind additionally freed those fields explicitly
before calling put_device(), causing further double frees on both.
Remove the redundant explicit kfree() calls from all setup error paths
and cleanup functions for wq, engine, and group structs, delegating
sole ownership of those allocations to the release callbacks.