CVE-2026-74593

In the Linux kernel, the following vulnerability has been resolved:

sched_ext: Take cgroup_lock() first in scx_cgroup_lock()

scx_cgroup_lock() write-locks scx_cgroup_ops_rwsem and then takes

cgroup_lock(), which can deadlock through kernfs:

scx enable/disable cgroup rmdir cpu.weight write

------------------ ------------ ----------------

cgroup_lock()

percpu_down_write(rwsem)

cgroup_lock()

kernfs_get_active()

percpu_down_read(rwsem)

kernfs_drain()

The enable path waits for the rmdir to release cgroup_mutex. The rmdir,

deactivating the cpu controller's files, waits in kernfs_drain() for the

write's active reference. The write, in scx_group_set_weight(), waits for

the rwsem behind the pending writer.

Take cgroup_lock() first. The set_* paths take no cgroup locks inside the

read side, so a pending write-lock then only waits for read sections that

always run to completion, and no dependency from the rwsem back to

cgroup_mutex remains.