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sched_ext: Avoid UAF in scx_root_enable_workfn() init failure path

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In scx_root_enable_workfn(), put_task_struct(p) is called before scx_error()
dereferences p->comm and p->pid. If the iterator's reference is the last
drop, the task is freed synchronously and the deref becomes a UAF.

Move put_task_struct() past scx_error().

Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://lore.kernel.org/all/20260511214031.AF5E9C2BCB0@smtp.kernel.org/
Fixes: f0e1a0643a ("sched_ext: Implement BPF extensible scheduler class")
Cc: stable@vger.kernel.org # v6.12+
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2026-05-11 12:05:48 -10:00
parent 86ecb1c1a1
commit 9a415cc537
1 changed files with 1 additions and 1 deletions
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2
kernel/sched/ext.c
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@ -6973,10 +6973,10 @@ static void scx_root_enable_workfn(struct kthread_work *work)
if (scx_get_task_state(p) != SCX_TASK_DEAD) if (scx_get_task_state(p) != SCX_TASK_DEAD)
scx_set_task_state(p, SCX_TASK_NONE); scx_set_task_state(p, SCX_TASK_NONE);
task_rq_unlock(rq, p, &rf); task_rq_unlock(rq, p, &rf);
put_task_struct(p);
scx_task_iter_stop(&sti); scx_task_iter_stop(&sti);
scx_error(sch, "ops.init_task() failed (%d) for %s[%d]", scx_error(sch, "ops.init_task() failed (%d) for %s[%d]",
ret, p->comm, p->pid); ret, p->comm, p->pid);
put_task_struct(p);
goto err_disable_unlock_all; goto err_disable_unlock_all;
} }