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

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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: 4c30f5ce4f ("sched_ext: Implement scx_bpf_dispatch[_vtime]_from_dsq()")
Cc: stable@vger.kernel.org # v6.12+
Reported-by: Chris Mason <clm@meta.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
This commit is contained in:
Tejun Heo 2026-04-24 14:31:35 -10:00
parent 411d3ef1a7
commit 4fda9f0e7c
1 changed files with 11 additions and 1 deletions
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12
kernel/sched/ext.c
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@ -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;