From: Michael Kelley <mhkli...@outlook.com> Current code allocates the pcpu_sum array with size num_possible_cpus(). This code assumes the cpu_possible_mask is dense, which is not true in the general case per [1]. If cpu_possible_mask is sparse, the array might be indexed by a value beyond the size of the array.
However, the configurations that Hyper-V provides to guest VMs on x86 and ARM64 hardware, in combination with how architecture specific code assigns Linux CPU numbers, *does* always produce a dense cpu_possible_mask. So the dense assumption is not currently causing failures. But for robustness against future changes in how cpu_possible_mask is populated, update the code to no longer assume dense. The correct approach is to allocate and initialize the array using size "nr_cpu_ids". While this leaves unused array entries corresponding to holes in cpu_possible_mask, the holes are assumed to be minimal and hence the amount of memory wasted by unused entries is minimal. [1] https://lore.kernel.org/lkml/sn6pr02mb4157210cc36b2593f8572e5ed4...@sn6pr02mb4157.namprd02.prod.outlook.com/ Signed-off-by: Michael Kelley <mhkli...@outlook.com> --- drivers/net/hyperv/netvsc_drv.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c index 153b97f8ec0d..f8e2dd6d271d 100644 --- a/drivers/net/hyperv/netvsc_drv.c +++ b/drivers/net/hyperv/netvsc_drv.c @@ -1557,7 +1557,7 @@ static void netvsc_get_ethtool_stats(struct net_device *dev, data[i++] = xdp_tx; } - pcpu_sum = kvmalloc_array(num_possible_cpus(), + pcpu_sum = kvmalloc_array(nr_cpu_ids, sizeof(struct netvsc_ethtool_pcpu_stats), GFP_KERNEL); if (!pcpu_sum) -- 2.25.1
