Description

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.

Weaknesses 1

Affected Products 3

References 3

• git.kernel.org https://git.kernel.org/stable/c/0f54f6355575971673d8aac7da107ec4178e45bd
  Patch
• git.kernel.org https://git.kernel.org/stable/c/80afd4c84bc8f5e80145ce35279f5ce53f6043db
  Patch
• git.kernel.org https://git.kernel.org/stable/c/ce9aaa3af445c391735c9d000c4db60dfd5640d4
  Patch

Remediation

• git.kernel.org https://git.kernel.org/stable/c/0f54f6355575971673d8aac7da107ec4178e45bd
  Patch
• git.kernel.org https://git.kernel.org/stable/c/80afd4c84bc8f5e80145ce35279f5ce53f6043db
  Patch
• git.kernel.org https://git.kernel.org/stable/c/ce9aaa3af445c391735c9d000c4db60dfd5640d4
  Patch