From: Eric Dumazet <eric.dumazet@gmail.com>
To: izabela.bakollari@gmail.com, nhorman@tuxdriver.com,
davem@davemloft.net, kuba@kernel.org
Cc: netdev@vger.kernel.org,
linux-kernel-mentees@lists.linuxfoundation.org,
linux-kernel@vger.kernel.org
Subject: Re: [Linux-kernel-mentees] [PATCHv3 net-next] dropwatch: Support monitoring of dropped frames
Date: Wed, 2 Sep 2020 22:35:00 +0200 [thread overview]
Message-ID: <0b27311f-6836-45e8-6bb3-d741d37d135b@gmail.com> (raw)
In-Reply-To: <20200902171604.109864-1-izabela.bakollari@gmail.com>
On 9/2/20 10:16 AM, izabela.bakollari@gmail.com wrote:
> From: Izabela Bakollari <izabela.bakollari@gmail.com>
>
> Dropwatch is a utility that monitors dropped frames by having userspace
> record them over the dropwatch protocol over a file. This augument
> allows live monitoring of dropped frames using tools like tcpdump.
>
> With this feature, dropwatch allows two additional commands (start and
> stop interface) which allows the assignment of a net_device to the
> dropwatch protocol. When assinged, dropwatch will clone dropped frames,
> and receive them on the assigned interface, allowing tools like tcpdump
> to monitor for them.
>
> With this feature, create a dummy ethernet interface (ip link add dev
> dummy0 type dummy), assign it to the dropwatch kernel subsystem, by using
> these new commands, and then monitor dropped frames in real time by
> running tcpdump -i dummy0.
>
> Signed-off-by: Izabela Bakollari <izabela.bakollari@gmail.com>
> ---
> Changes in v3:
> - Name the cloned skb "nskb"
> - Remove the error log
> - Change coding style in some if statements
> ---
> include/uapi/linux/net_dropmon.h | 3 ++
> net/core/drop_monitor.c | 80 ++++++++++++++++++++++++++++++++
> 2 files changed, 83 insertions(+)
>
> diff --git a/include/uapi/linux/net_dropmon.h b/include/uapi/linux/net_dropmon.h
> index 67e31f329190..e8e861e03a8a 100644
> --- a/include/uapi/linux/net_dropmon.h
> +++ b/include/uapi/linux/net_dropmon.h
> @@ -58,6 +58,8 @@ enum {
> NET_DM_CMD_CONFIG_NEW,
> NET_DM_CMD_STATS_GET,
> NET_DM_CMD_STATS_NEW,
> + NET_DM_CMD_START_IFC,
> + NET_DM_CMD_STOP_IFC,
> _NET_DM_CMD_MAX,
> };
>
> @@ -93,6 +95,7 @@ enum net_dm_attr {
> NET_DM_ATTR_SW_DROPS, /* flag */
> NET_DM_ATTR_HW_DROPS, /* flag */
> NET_DM_ATTR_FLOW_ACTION_COOKIE, /* binary */
> + NET_DM_ATTR_IFNAME, /* string */
>
> __NET_DM_ATTR_MAX,
> NET_DM_ATTR_MAX = __NET_DM_ATTR_MAX - 1
> diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
> index 8e33cec9fc4e..ae5ed70b6b2a 100644
> --- a/net/core/drop_monitor.c
> +++ b/net/core/drop_monitor.c
> @@ -30,6 +30,7 @@
> #include <net/genetlink.h>
> #include <net/netevent.h>
> #include <net/flow_offload.h>
> +#include <net/sock.h>
>
> #include <trace/events/skb.h>
> #include <trace/events/napi.h>
> @@ -46,6 +47,7 @@
> */
> static int trace_state = TRACE_OFF;
> static bool monitor_hw;
> +struct net_device *interface;
>
> /* net_dm_mutex
> *
> @@ -54,6 +56,8 @@ static bool monitor_hw;
> */
> static DEFINE_MUTEX(net_dm_mutex);
>
> +static DEFINE_SPINLOCK(interface_lock);
> +
> struct net_dm_stats {
> u64 dropped;
> struct u64_stats_sync syncp;
> @@ -217,6 +221,7 @@ static void trace_drop_common(struct sk_buff *skb, void *location)
> struct nlattr *nla;
> int i;
> struct sk_buff *dskb;
> + struct sk_buff *nskb;
> struct per_cpu_dm_data *data;
> unsigned long flags;
>
> @@ -255,6 +260,18 @@ static void trace_drop_common(struct sk_buff *skb, void *location)
>
> out:
> spin_unlock_irqrestore(&data->lock, flags);
> + spin_lock_irqsave(&interface_lock, flags);
> + nskb = skb_clone(skb, GFP_ATOMIC);
1) Why calling skb_clone() if @interface is NULL ?
> + if (!nskb) {
> + spin_unlock_irqrestore(&interface_lock, flags);
> + return;
> + } else if (interface && interface != nskb->dev) {
2) Since there is no check about @interface being a dummy device,
it seems possible for a malicious user to set up another virtual
device (like bonding) so that the "interface != nskb->dev" test
wont be able to detect a loop.
We could therefore have an infinite loop.
> + nskb->dev = interface;
> + spin_unlock_irqrestore(&interface_lock, flags);
> + netif_receive_skb(nskb);
> + } else {
3) nskb seems to be leaked here ? See point 1)
> + spin_unlock_irqrestore(&interface_lock, flags);
> + }
> }
>
> static void trace_kfree_skb_hit(void *ignore, struct sk_buff *skb, void *location)
> @@ -1315,6 +1332,51 @@ static int net_dm_cmd_trace(struct sk_buff *skb,
> return -EOPNOTSUPP;
> }
>
> +static int net_dm_interface_start(struct net *net, const char *ifname)
> +{
> + struct net_device *nd = dev_get_by_name(net, ifname);
> +
> + if (!nd)
> + return -ENODEV;
> +
> + interface = nd;
> +
> + return 0;
> +}
> +
> +static int net_dm_interface_stop(struct net *net, const char *ifname)
> +{
> + dev_put(interface);
> + interface = NULL;
> +
> + return 0;
> +}
> +
> +static int net_dm_cmd_ifc_trace(struct sk_buff *skb, struct genl_info *info)
> +{
> + struct net *net = sock_net(skb->sk);
> + char ifname[IFNAMSIZ];
> +
> + if (net_dm_is_monitoring())
> + return -EBUSY;
> +
> + memset(ifname, 0, IFNAMSIZ);
> + nla_strlcpy(ifname, info->attrs[NET_DM_ATTR_IFNAME], IFNAMSIZ - 1);
4) info->attrs[NET_DM_ATTR_IFNAME] could be NULL at this point.
> +
> + switch (info->genlhdr->cmd) {
> + case NET_DM_CMD_START_IFC:
5) interface_lock is not held, this seems racy.
> + if (interface)
> + return -EBUSY;
> + return net_dm_interface_start(net, ifname);
> + case NET_DM_CMD_STOP_IFC:
6) interface_lock is not held, this seems racy.
> + if (!interface)
> + return -ENODEV;
> + return net_dm_interface_stop(net, interface->name);
> + }
> +
> + return 0;
> +}
> +
> static int net_dm_config_fill(struct sk_buff *msg, struct genl_info *info)
> {
> void *hdr;
> @@ -1503,6 +1565,7 @@ static int dropmon_net_event(struct notifier_block *ev_block,
> struct net_device *dev = netdev_notifier_info_to_dev(ptr);
> struct dm_hw_stat_delta *new_stat = NULL;
> struct dm_hw_stat_delta *tmp;
> + unsigned long flags;
>
> switch (event) {
> case NETDEV_REGISTER:
> @@ -1529,6 +1592,12 @@ static int dropmon_net_event(struct notifier_block *ev_block,
> }
> }
> }
> + spin_lock_irqsave(&interface_lock, flags);
> + if (interface && interface == dev) {
> + dev_put(interface);
> + interface = NULL;
> + }
> + spin_unlock_irqrestore(&interface_lock, flags);
> mutex_unlock(&net_dm_mutex);
> break;
> }
> @@ -1543,6 +1612,7 @@ static const struct nla_policy net_dm_nl_policy[NET_DM_ATTR_MAX + 1] = {
> [NET_DM_ATTR_QUEUE_LEN] = { .type = NLA_U32 },
> [NET_DM_ATTR_SW_DROPS] = {. type = NLA_FLAG },
> [NET_DM_ATTR_HW_DROPS] = {. type = NLA_FLAG },
> + [NET_DM_ATTR_IFNAME] = {. type = NLA_STRING, .len = IFNAMSIZ },
> };
>
> static const struct genl_ops dropmon_ops[] = {
> @@ -1570,6 +1640,16 @@ static const struct genl_ops dropmon_ops[] = {
> .cmd = NET_DM_CMD_STATS_GET,
> .doit = net_dm_cmd_stats_get,
> },
> + {
> + .cmd = NET_DM_CMD_START_IFC,
> + .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
> + .doit = net_dm_cmd_ifc_trace,
> + },
> + {
> + .cmd = NET_DM_CMD_STOP_IFC,
> + .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
> + .doit = net_dm_cmd_ifc_trace,
> + },
> };
>
> static int net_dm_nl_pre_doit(const struct genl_ops *ops,
>
_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
next prev parent reply other threads:[~2020-09-02 20:35 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-07 17:15 [Linux-kernel-mentees] [PATCH net-next] dropwatch: Support monitoring of dropped frames izabela.bakollari
2020-07-07 17:33 ` Eric Dumazet
2020-07-07 17:36 ` Eric Dumazet
2020-07-07 17:52 ` Eric Dumazet
2020-07-08 13:54 ` Izabela Bakollari
2020-07-08 14:06 ` Izabela Bakollari
2020-07-07 21:00 ` kernel test robot
2020-07-08 0:27 ` kernel test robot
2020-08-04 16:09 ` [Linux-kernel-mentees] [PATCHv2 " izabela.bakollari
2020-08-04 21:28 ` Cong Wang
2020-08-04 21:58 ` Neil Horman
2020-08-04 23:14 ` David Miller
2020-08-05 10:44 ` Neil Horman
2020-08-10 13:39 ` Izabela Bakollari
2020-08-10 13:56 ` Greg KH
2020-08-31 13:18 ` Michal Schmidt
2020-09-02 16:05 ` Izabela Bakollari
2020-09-02 17:16 ` [Linux-kernel-mentees] [PATCHv3 " izabela.bakollari
2020-09-02 20:35 ` Eric Dumazet [this message]
2020-10-23 4:29 ` [Linux-kernel-mentees] [PATCHv4 " izabela.bakollari
2020-10-23 18:20 ` Jakub Kicinski
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=0b27311f-6836-45e8-6bb3-d741d37d135b@gmail.com \
--to=eric.dumazet@gmail.com \
--cc=davem@davemloft.net \
--cc=izabela.bakollari@gmail.com \
--cc=kuba@kernel.org \
--cc=linux-kernel-mentees@lists.linuxfoundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=nhorman@tuxdriver.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).