From: Michael Kelley Date: Thu, 3 Oct 2024 03:53:33 +0000 (-0700) Subject: hv_netvsc: Don't assume cpu_possible_mask is dense X-Git-Tag: v6.13-rc1~135^2~418 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c86ab60b92d1f3471a56c8bd0856ca78e705f0f0;p=thirdparty%2Fkernel%2Flinux.git hv_netvsc: Don't assume cpu_possible_mask is dense 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/SN6PR02MB4157210CC36B2593F8572E5ED4692@SN6PR02MB4157.namprd02.prod.outlook.com/ Signed-off-by: Michael Kelley Acked-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/20241003035333.49261-6-mhklinux@outlook.com Signed-off-by: Jakub Kicinski --- diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c index 153b97f8ec0df..f8e2dd6d271df 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)