Messages in this thread Patch in this message | | | From | Ameen Ali <> | Subject | [PATCH 4/4] net/core/dev.c : Race condition in net_tx_action. | Date | Wed, 25 Feb 2015 19:50:59 +0200 |
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Transmitting asynchronously on all the network devices available we will notice the following behaviour: a) The instruction "if (sd->completion_queue) {" saves on a CPU register the pointer value (register contents is used for the comparison) b) The interupt is disabled (using "local_irq_disable") c) when the content of "clist" is updated, the register is used, instead of re-read the "completion_queue" variable.
So, when a low-level tx interrupt arrives after the latching of "completion_queue", but before "local_irq_disable", the value stored in "clist" reflect the situation before low-level tx interrupt, resulting in a sk_buff leak --- net/core/dev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/core/dev.c b/net/core/dev.c index 8f9710c..db3e59e 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3413,7 +3413,7 @@ EXPORT_SYMBOL(netif_rx_ni); static void net_tx_action(struct softirq_action *h) { - struct softnet_data *sd = this_cpu_ptr(&softnet_data); + volatile struct softnet_data *sd = &__get_cpu_var(softnet_data); if (sd->completion_queue) { struct sk_buff *clist; -- 2.1.0
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