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Change History

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

sched_ext: Read scx_root under scx_cgroup_ops_rwsem in cgroup setters

scx_group_set_{weight,idle,bandwidth}() cache scx_root before acquiring
scx_cgroup_ops_rwsem, so the pointer can be stale by the time the op runs.
If the loaded scheduler is disabled and freed (via RCU work) and another is
enabled between the naked load and the rwsem acquire, the reader sees
scx_cgroup_enabled=true (the new scheduler's) but dereferences the freed one
- UAF on SCX_HAS_OP(sch, ...) / SCX_CALL_OP(sch, ...).

scx_cgroup_enabled is toggled only under scx_cgroup_ops_rwsem write
(scx_cgroup_{init,exit}), so reading scx_root inside the rwsem read section
correlates @sch with the enabled snapshot.

https://git.kernel.org/stable/c/0f54f6355575971673d8aac7da107ec4178e45bd

https://git.kernel.org/stable/c/80afd4c84bc8f5e80145ce35279f5ce53f6043db

https://git.kernel.org/stable/c/ce9aaa3af445c391735c9d000c4db60dfd5640d4