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[204.195.112.199]) by smtp.gmail.com with ESMTPSA id v14-20020a056a00148e00b004e1cee6f6b4sm12178835pfu.47.2022.03.11.09.25.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Mar 2022 09:25:41 -0800 (PST) Date: Fri, 11 Mar 2022 09:25:38 -0800 From: Stephen Hemminger To: Jiasheng Jiang Cc: kys@microsoft.com, haiyangz@microsoft.com, sthemmin@microsoft.com, wei.liu@kernel.org, decui@microsoft.com, davem@davemloft.net, kuba@kernel.org, ast@kernel.org, daniel@iogearbox.net, hawk@kernel.org, john.fastabend@gmail.com, andrii@kernel.org, kafai@fb.com, songliubraving@fb.com, yhs@fb.com, kpsingh@kernel.org, linux-hyperv@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [PATCH] hv_netvsc: Add check for kvmalloc_array Message-ID: <20220311092538.0cb478cf@hermes.local> In-Reply-To: <20220311032035.2037962-1-jiasheng@iscas.ac.cn> References: <20220311032035.2037962-1-jiasheng@iscas.ac.cn> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, 11 Mar 2022 11:20:35 +0800 Jiasheng Jiang wrote: > As the potential failure of the kvmalloc_array(), > it should be better to check and restore the 'data' > if fails in order to avoid the dereference of the > NULL pointer. > > Fixes: 6ae746711263 ("hv_netvsc: Add per-cpu ethtool stats for netvsc") > Signed-off-by: Jiasheng Jiang > --- > drivers/net/hyperv/netvsc_drv.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c > index 3646469433b1..018c4a5f6f44 100644 > --- a/drivers/net/hyperv/netvsc_drv.c > +++ b/drivers/net/hyperv/netvsc_drv.c > @@ -1587,6 +1587,12 @@ static void netvsc_get_ethtool_stats(struct net_device *dev, > pcpu_sum = kvmalloc_array(num_possible_cpus(), > sizeof(struct netvsc_ethtool_pcpu_stats), > GFP_KERNEL); > + if (!pcpu_sum) { > + for (j = 0; j < i; j++) > + data[j] = 0; > + return; > + } I don't think you understood what my comment was. The zeroing here is not necessary. Just do: if (!pcpu_sum) return; The data pointer is to buffer allocated here: static int ethtool_get_stats(struct net_device *dev, void __user *useraddr) { ... if (n_stats) { data = vzalloc(array_size(n_stats, sizeof(u64))); <<<<< is already zeroed. if (!data) return -ENOMEM; ops->get_ethtool_stats(dev, &stats, data);