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xdp: fix bug in cpumap teardown code path
When removing a cpumap entry, a number of syncronization steps happen.
Eventually the teardown code __cpu_map_entry_free is invoked from/via
call_rcu.
The teardown code __cpu_map_entry_free() flushes remaining xdp_frames,
by invoking bq_flush_to_queue, which calls xdp_return_frame_rx_napi().
The issues is that the teardown code is not running in the RX NAPI
code path. Thus, it is not allowed to invoke the NAPI variant of
xdp_return_frame.
This bug was found and triggered by using the --stress-mode option to
the samples/bpf program xdp_redirect_cpu. It is hard to trigger,
because the ptr_ring have to be full and cpumap bulk queue max
contains 8 packets, and a remote CPU is racing to empty the ptr_ring
queue.
Fixes: 389ab7f01a
("xdp: introduce xdp_return_frame_rx_napi")
Tested-by: Jean-Tsung Hsiao <jhsiao@redhat.com>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
parent
bf9bae0ea6
commit
ad0ab027fc
1 changed files with 9 additions and 6 deletions
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@ -69,7 +69,7 @@ struct bpf_cpu_map {
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};
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static int bq_flush_to_queue(struct bpf_cpu_map_entry *rcpu,
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struct xdp_bulk_queue *bq);
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struct xdp_bulk_queue *bq, bool in_napi_ctx);
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static u64 cpu_map_bitmap_size(const union bpf_attr *attr)
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{
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@ -375,7 +375,7 @@ static void __cpu_map_entry_free(struct rcu_head *rcu)
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struct xdp_bulk_queue *bq = per_cpu_ptr(rcpu->bulkq, cpu);
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/* No concurrent bq_enqueue can run at this point */
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bq_flush_to_queue(rcpu, bq);
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bq_flush_to_queue(rcpu, bq, false);
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}
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free_percpu(rcpu->bulkq);
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/* Cannot kthread_stop() here, last put free rcpu resources */
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@ -558,7 +558,7 @@ const struct bpf_map_ops cpu_map_ops = {
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};
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static int bq_flush_to_queue(struct bpf_cpu_map_entry *rcpu,
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struct xdp_bulk_queue *bq)
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struct xdp_bulk_queue *bq, bool in_napi_ctx)
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{
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unsigned int processed = 0, drops = 0;
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const int to_cpu = rcpu->cpu;
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@ -578,7 +578,10 @@ static int bq_flush_to_queue(struct bpf_cpu_map_entry *rcpu,
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err = __ptr_ring_produce(q, xdpf);
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if (err) {
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drops++;
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xdp_return_frame_rx_napi(xdpf);
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if (likely(in_napi_ctx))
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xdp_return_frame_rx_napi(xdpf);
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else
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xdp_return_frame(xdpf);
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}
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processed++;
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}
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@ -598,7 +601,7 @@ static int bq_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_frame *xdpf)
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struct xdp_bulk_queue *bq = this_cpu_ptr(rcpu->bulkq);
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if (unlikely(bq->count == CPU_MAP_BULK_SIZE))
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bq_flush_to_queue(rcpu, bq);
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bq_flush_to_queue(rcpu, bq, true);
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/* Notice, xdp_buff/page MUST be queued here, long enough for
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* driver to code invoking us to finished, due to driver
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@ -661,7 +664,7 @@ void __cpu_map_flush(struct bpf_map *map)
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/* Flush all frames in bulkq to real queue */
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bq = this_cpu_ptr(rcpu->bulkq);
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bq_flush_to_queue(rcpu, bq);
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bq_flush_to_queue(rcpu, bq, true);
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/* If already running, costs spin_lock_irqsave + smb_mb */
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wake_up_process(rcpu->kthread);
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