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sched_ext: bpf_iter_scx_dsq_new() should always initialize iterator

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BPF programs may call next() and destroy() on BPF iterators even after new()
returns an error value (e.g. bpf_for_each() macro ignores error returns from
new()). bpf_iter_scx_dsq_new() could leave the iterator in an uninitialized
state after an error return causing bpf_iter_scx_dsq_next() to dereference
garbage data. Make bpf_iter_scx_dsq_new() always clear $kit->dsq so that
next() and destroy() become noops.

Signed-off-by: Tejun Heo <tj@kernel.org>
Fixes: 650ba21b13 ("sched_ext: Implement DSQ iterator")
Cc: stable@vger.kernel.org # v6.12+
Acked-by: Andrea Righi <arighi@nvidia.com>
This commit is contained in:
Tejun Heo 2025-05-05 11:30:39 -10:00
parent e38be1c764
commit 428dc9fc08
1 changed files with 6 additions and 0 deletions
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6
kernel/sched/ext.c
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@ -6827,6 +6827,12 @@ __bpf_kfunc int bpf_iter_scx_dsq_new(struct bpf_iter_scx_dsq *it, u64 dsq_id,
BUILD_BUG_ON(__alignof__(struct bpf_iter_scx_dsq_kern) !=
__alignof__(struct bpf_iter_scx_dsq));
/*
* next() and destroy() will be called regardless of the return value.
* Always clear $kit->dsq.
*/
kit->dsq = NULL;
if (flags & ~__SCX_DSQ_ITER_USER_FLAGS)
return -EINVAL;