Commit 4fda9f0e authored by Tejun Heo's avatar Tejun Heo
Browse files

sched_ext: Guard scx_dsq_move() against NULL kit->dsq after failed iter_new 



bpf_iter_scx_dsq_new() clears kit->dsq on failure and
bpf_iter_scx_dsq_{next,destroy}() guard against that. scx_dsq_move() doesn't -
it dereferences kit->dsq immediately, so a BPF program that calls
scx_bpf_dsq_move[_vtime]() after a failed iter_new oopses the kernel.

Return false if kit->dsq is NULL.

Fixes: 4c30f5ce ("sched_ext: Implement scx_bpf_dispatch[_vtime]_from_dsq()")
Cc: stable@vger.kernel.org # v6.12+
Reported-by: default avatarChris Mason <clm@meta.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarAndrea Righi <arighi@nvidia.com>
parent 411d3ef1

kernel/sched/ext.c

+11 −1
Original line number Diff line number Diff line
@@ -8076,12 +8076,22 @@ static bool scx_dsq_move(struct bpf_iter_scx_dsq_kern *kit, 
			 struct task_struct *p, u64 dsq_id, u64 enq_flags)

{

	struct scx_dispatch_q *src_dsq = kit->dsq, *dst_dsq;

	struct scx_sched *sch = src_dsq->sched;

	struct scx_sched *sch;

	struct rq *this_rq, *src_rq, *locked_rq;

	bool dispatched = false;

	bool in_balance;

	unsigned long flags;



	/*

	 * The verifier considers an iterator slot initialized on any

	 * KF_ITER_NEW return, so a BPF program may legally reach here after

	 * bpf_iter_scx_dsq_new() failed and left @kit->dsq NULL.

	 */

	if (unlikely(!src_dsq))

		return false;



	sch = src_dsq->sched;



	if (!scx_vet_enq_flags(sch, dsq_id, &enq_flags))

		return false;