sched_ext: Fix this_rq() assumptions in dispatch kfuncs

Summary

In the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix this_rq() assumptions in dispatch kfuncs Under core scheduling, dispatch runs from within the core-wide pick and can target a sibling rq, so ops.dispatch() may execute on a CPU different from the dispatched rq's. Several kfunc paths assumed the two always coincide: • scx_dsq_move() decided whether an rq lock is held by testing this_rq()'s rq flags and lock-danced accordingly. A dispatch for a sibling took the unlocked-context branch and acquired the source rq lock on top of the already held dispatched rq lock which could deadlock. • scx_bpf_sub_dispatch() dispatched this_rq() with its stashed sub_dispatch_prev, which is NULL when dispatching for a sibling. • finish_dispatch(), scx_bpf_dsq_reenq() and scx_bpf_dsq_nr_queued() resolved SCX_DSQ_LOCAL to this CPU's local DSQ rather than the dispatched rq's. The latter two are callable from other rq-locked operations too, where SCX_DSQ_LOCAL now likewise resolves to the op's rq. This changes behavior also without core scheduling, e.g. for ops.enqueue() running a remote wakeup on the waking CPU, and is intended: which CPU happens to execute an operation is incidental, the op's rq is what it is operating on, and the resolution now matches the insert side where SCX_DSQ_LOCAL dispatches land on the task's rq. Use the rq tracked by scx_locked_rq(), which is set to the dispatched rq around ops invocations and NULL in unlocked contexts.

Timeline

1. Sep 11, 2026, 7:44 PM UTCCVE published
2. Oct 19, 2026, 8:48 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 4c95380701f58b8112f0b891de8d160e4199e19d · fixed in 6d1890d3c6137ab523799765ae2de62cc05f116d; From 4c95380701f58b8112f0b891de8d160e4199e19d · fixed in 3dd52416e44a70bc993adb96d2e0d71b9ea21359

• Linux Linux

  6.19

• KernelLinux

  From 6.19.0 · fixed in 7.2.4

References 2