We precompute the static-static ECDH during configuration time, in order
to save an expensive computation later when receiving network packets.
However, not all ECDH computations yield a contributory result. Prior,
we were just not letting those peers be added to the interface. However,
this creates a strange inconsistency, since it was still possible to add
other weird points, like a valid public key plus a low-order point, and,
like points that result in zeros, a handshake would not complete. In
order to make the behavior more uniform and less surprising, simply
allow all peers to be added. Then, we'll error out later when doing the
crypto if there's an issue. This also adds more separation between the
crypto layer and the configuration layer.

Discussed-with: Mathias Hall-Andersen <mathias@hall-andersen.dk>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The situation in which we wind up hitting the default case here
indicates a major bug in earlier parsing code. It is not a usual thing
that should ever happen, which means a "friendly" message for it doesn't
make sense. Rather, replace this with a WARN_ON, just like we do earlier
in the file for a similar situation, so that somebody sends us a bug
report and we can fix it.
Reported-by: Fabian Freyer <fabianfreyer@radicallyopensecurity.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

We carry out checks to the effect of:

  if (skb->protocol != wg_examine_packet_protocol(skb))
    goto err;

By having wg_skb_examine_untrusted_ip_hdr return 0 on failure, this
means that the check above still passes in the case where skb->protocol
is zero, which is possible to hit with AF_PACKET:

  struct sockaddr_pkt saddr = { .spkt_device = "wg0" };
  unsigned char buffer[5] = { 0 };
  sendto(socket(AF_PACKET, SOCK_PACKET, /* skb->protocol = */ 0),
         buffer, sizeof(buffer), 0, (const struct sockaddr *)&saddr, sizeof(saddr));

Additional checks mean that this isn't actually a problem in the code
base, but I could imagine it becoming a problem later if the function is
used more liberally.

I would prefer to fix this by having wg_examine_packet_protocol return a
32-bit ~0 value on failure, which will never match any value of
skb->protocol, which would simply change the generated code from a mov
to a movzx. However, sparse complains, and adding __force casts doesn't
seem like a good idea, so instead we just add a simple helper function
to check for the zero return value. Since wg_examine_packet_protocol
itself gets inlined, this winds up not adding an additional branch to
the generated code, since the 0 return value already happens in a
mergable branch.
Reported-by: Fabian Freyer <fabianfreyer@radicallyopensecurity.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

In case this helps expose bugs with the newer 64-bit time_t types, we do
our testing with the newer musl that supports this as well as
CONFIG_COMPAT_32BIT_TIME=n. This matters to us, since wireguard does in
fact deal with timestamps.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This commit removes a duplicated include.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

gro_cells_init() returns error if memory allocation is failed.
But the vxlan module doesn't check the return value of gro_cells_init().

Fixes: 58ce31cc ("vxlan: GRO support at tunnel layer")`
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Currently, on replace, the previous action instance params
is swapped with a newly allocated params. The old params is
only freed (via kfree_rcu), without releasing the allocated
ct zone template related to it.

Call tcf_ct_params_free (via call_rcu) for the old params,
so it will release it.

Fixes: b57dc7c1 ("net/sched: Introduce action ct")
Signed-off-by: Paul Blakey <paulb@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

There's a markup for link with is "foo_". On this kernel-doc
comment, we don't want this, but instead, place a literal
reference. So, escape the literal with ``foo``, in order to
avoid this warning:

	./net/core/dev.c:5195: WARNING: Unknown target name: "page_is".
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

The indentation for the returned values are weird, causing those
warnings:

	./drivers/net/phy/sfp-bus.c:579: WARNING: Unexpected indentation.
	./drivers/net/phy/sfp-bus.c:619: WARNING: Unexpected indentation.

Use a list and change the identation for it to be properly
parsed by the documentation toolchain.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Arthur Kiyanovski says:

====================
ENA driver bug fixes
====================
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

last_keep_alive_jiffies is updated in probe and when a keep-alive
event is received.  In case the driver times-out on a keep-alive event,
it has high chances of continuously timing-out on keep-alive events.
This is because when the driver recovers from the keep-alive-timeout reset
the value of last_keep_alive_jiffies is very old, and if a keep-alive
event is not received before the next timer expires, the value of
last_keep_alive_jiffies will cause another keep-alive-timeout reset
and so forth in a loop.

Solution:
Update last_keep_alive_jiffies whenever the device is restored after
reset.

Fixes: 1738cd3e ("net: ena: Add a driver for Amazon Elastic Network Adapters (ENA)")
Signed-off-by: Noam Dagan <ndagan@amazon.com>
Signed-off-by: Arthur Kiyanovski <akiyano@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Rx req_id is an index in struct ena_eth_io_rx_cdesc_base.
The driver should validate that the Rx req_id it received from
the device is in range [0, ring_size -1].  Failure to do so could
yield to potential memory access violoation.
The validation was mistakenly done when refilling
the Rx submission queue and not in Rx completion queue.

Fixes: ad974bae ("net: ena: add support for out of order rx buffers refill")
Signed-off-by: Noam Dagan <ndagan@amazon.com>
Signed-off-by: Arthur Kiyanovski <akiyano@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Bug:
In short the main issue is caused by the fact that the number of queues
is changed using ethtool after ena_probe() has been called and before
ena_up() was executed. Here is the full scenario in detail:

* ena_probe() is called when the driver is loaded, the driver is not up
  yet at the end of ena_probe().
* The number of queues is changed -> io_queue_count is changed as well -
  ena_up() is not called since the "dev_was_up" boolean in
  ena_update_queue_count() is false.
* ena_up() is called by the kernel (it's called asynchronously some
  time after ena_probe()). ena_setup_io_intr() is called by ena_up() and
  it uses io_queue_count to get the suitable irq lines for each msix
  vector. The function ena_request_io_irq() is called right after that
  and it uses msix_vecs - This value only changes during ena_probe() and
  ena_restore() - to request the irq vectors. This results in "Failed to
  request I/O IRQ" error for i > io_queue_count.

Numeric example:
* After ena_probe() io_queue_count = 8, msix_vecs = 9.
* The number of queues changes to 4 -> io_queue_count = 4, msix_vecs = 9.
* ena_up() is executed for the first time:
  ** ena_setup_io_intr() inits the vectors only up to io_queue_count.
  ** ena_request_io_irq() calls request_irq() and fails for i = 5.

How to reproduce:
simply run the following commands:
    sudo rmmod ena && sudo insmod ena.ko;
    sudo ethtool -L eth1 combined 3;

Fix:
Use ENA_MAX_MSIX_VEC(adapter->num_io_queues + adapter->xdp_num_queues)
instead of adapter->msix_vecs. We need to take XDP queues into
consideration as they need to have msix vectors assigned to them as well.
Note that the XDP cannot be attached before the driver is up and running
but in XDP mode the issue might occur when the number of queues changes
right after a reset trigger.
The ENA_MAX_MSIX_VEC simply adds one to the argument since the first msix
vector is reserved for management queue.

Fixes: 1738cd3e ("net: ena: Add a driver for Amazon Elastic Network Adapters (ENA)")
Signed-off-by: Sameeh Jubran <sameehj@amazon.com>
Signed-off-by: Arthur Kiyanovski <akiyano@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Overview:
We don't frequently change the msix vectors throughout the life cycle of
the driver. We do so in two functions: ena_probe() and ena_restore().
ena_probe() is only called when the driver is loaded. ena_restore() on the
other hand is called during device reset / resume operations.

We use num_io_queues for calculating and allocating the number of msix
vectors. At ena_probe() this value is equal to max_num_io_queues and thus
this is not an issue, however ena_restore() might be called after the
number of io queues has changed.

A possible bug scenario is as follows:

* Change number of queues from 8 to 4.
  (num_io_queues = 4, max_num_io_queues = 8, msix_vecs = 9,)
* Trigger reset occurs -> ena_restore is called.
  (num_io_queues = 4, max_num_io_queues =8 , msix_vecs = 5)
* Change number of queues from 4 to 6.
  (num_io_queues = 6, max_num_io_queues = 8, msix_vecs = 5)
* The driver will reset due to failure of check_for_rx_interrupt_queue()

Fix:
This can be easily fixed by always using max_num_io_queues to init the
msix_vecs, since this number won't change as opposed to num_io_queues.

Fixes: 4d192660 ("net: ena: multiple queue creation related cleanups")
Signed-off-by: Sameeh Jubran <sameehj@amazon.com>
Signed-off-by: Arthur Kiyanovski <akiyano@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Check clk_prepare_enable() return value.

Fixes: 2c723044 ("net: phy: Add pm support to Broadcom iProc mdio mux driver")
Signed-off-by: Rayagonda Kokatanur <rayagonda.kokatanur@broadcom.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

Doug Berger says:

====================
net: bcmgenet: revisit MAC reset

Commit 3a55402c ("net: bcmgenet: use RGMII loopback for MAC
reset") was intended to resolve issues with reseting the UniMAC
core within the GENET block by providing better control over the
clocks used by the UniMAC core. Unfortunately, it is not
compatible with all of the supported system configurations so an
alternative method must be applied.

This commit set provides such an alternative. The first commit
reverts the previous change and the second commit provides the
alternative reset sequence that addresses the concerns observed
with the previous implementation.

This replacement implementation should be applied to the stable
branches wherever commit 3a55402c ("net: bcmgenet: use RGMII
loopback for MAC reset") has been applied.

Unfortunately, reverting that commit may conflict with some
restructuring changes introduced by commit 4f8d81b7 ("net:
bcmgenet: Refactor register access in bcmgenet_mii_config").
The first commit in this set has been manually edited to
resolve the conflict on net/master. I would be happy to help
stable maintainers with resolving any such conflicts if they
occur. However, I do not expect that commit to have been
backported to stable branch so hopefully the revert can be
applied cleanly.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

As noted in commit 28c2d1a7 ("net: bcmgenet: enable loopback
during UniMAC sw_reset") the UniMAC must be clocked at least 5
cycles while the sw_reset is asserted to ensure a clean reset.

That commit enabled local loopback to provide an Rx clock from the
GENET sourced Tx clk. However, when connected in MII mode the Tx
clk is sourced by the PHY so if an EPHY is not supplying clocks
(e.g. when the link is down) the UniMAC does not receive the
necessary clocks.

This commit extends the sw_reset window until the PHY reports that
the link is up thereby ensuring that the clocks are being provided
to the MAC to produce a clean reset.

One consequence is that if the system attempts to enter a Wake on
LAN suspend state when the PHY link has not been active the MAC
may not have had a chance to initialize cleanly. In this case, we
remove the sw_reset and enable the WoL reception path as normal
with the hope that the PHY will provide the necessary clocks to
drive the WoL blocks if the link becomes active after the system
has entered suspend.

Fixes: 1c1008c7 ("net: bcmgenet: add main driver file")
Signed-off-by: Doug Berger <opendmb@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This reverts commit 3a55402c.

This is not a good solution when connecting to an external switch
that may not support the isolation of the TXC signal resulting in
output driver contention on the pin.

A different solution is necessary.
Signed-off-by: Doug Berger <opendmb@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Chris Packham says:

====================
net: mvmdio: avoid error message for optional IRQ

I've gone ahead an sent a revert. This is the same as the original v1 except
I've added Andrew's review to the commit message.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Per the dt-binding the interrupt is optional so use
platform_get_irq_optional() instead of platform_get_irq(). Since
commit 7723f4c5 ("driver core: platform: Add an error message to
platform_get_irq*()") platform_get_irq() produces an error message

  orion-mdio f1072004.mdio: IRQ index 0 not found

which is perfectly normal if one hasn't specified the optional property
in the device tree.
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

This reverts commit e1f550dc.
platform_get_irq_optional() will still return -ENXIO when no interrupt
is provided so the additional error handling caused the driver prone to
fail when no interrupt was specified. Revert the change so we can apply
the correct minimal fix.
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

The fix referenced below causes a crash when an ERSPAN tunnel is created
without passing IFLA_INFO_DATA. Fix by validating passed-in data in the
same way as ipgre does.

Fixes: e1f8f78f ("net: ip_gre: Separate ERSPAN newlink / changelink callbacks")
Reported-by: syzbot+1b4ebf4dae4e510dd219@syzkaller.appspotmail.com
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

For the case where the last mvneta_poll did not process all
RX packets, we need to xor the pp->cause_rx_tx or port->cause_rx_tx
before claculating the rx_queue.

Fixes: 2dcf75e2 ("net: mvneta: Associate RX queues with each CPU")
Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

printk in macro vxge_debug_ll uses __VA_ARGS__ without "##" prefix,
it causes a build error when there is no variable
arguments(e.g. only fmt is specified.).
Signed-off-by: Zheng Wei <wei.zheng@vivo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Madalin Bucur says:

====================
QorIQ DPAA ARM RDBs need internal delay on RGMII

v2: used phy_interface_mode_is_rgmii() to identify RGMII

The QorIQ DPAA 1 based RDB boards require internal delay on
both Tx and Rx to be set. The patch set ensures all RGMII
modes are treated correctly by the FMan driver and sets the
phy-connection-type to "rgmii-id" to restore functionality.
Previously Rx internal delay was set by board pull-ups and
was left untouched by the PHY driver. Since commit
1b3047b5 ("net: phy: realtek: add support for
configuring the RX delay on RTL8211F") the Realtek 8211F PHY
driver has control over the RGMII RX delay and it is
disabling it for other modes than RGMII_RXID and RGMII_ID.

Please note that u-boot in particular performs a fix-up of
the PHY connection type and will overwrite the values from
the Linux device tree. Another patch set was sent for u-boot
and one needs to apply that [1] to the boot loader, to ensure
this fix is complete, unless a different bootloader is used.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

The correct setting for the RGMII ports on LS1046ARDB is to
enable delay on both Rx and Tx so the interface mode used must
be PHY_INTERFACE_MODE_RGMII_ID.

Since commit 1b3047b5 ("net: phy: realtek: add support for
configuring the RX delay on RTL8211F") the Realtek 8211F PHY driver
has control over the RGMII RX delay and it is disabling it for
RGMII_TXID. The LS1046ARDB uses two such PHYs in RGMII_ID mode but
in the device tree the mode was described as "rgmii".

Changing the phy-connection-type to "rgmii-id" to address the issue.

Fixes: 3fa395d2 ("arm64: dts: add LS1046A DPAA FMan nodes")
Signed-off-by: Madalin Bucur <madalin.bucur@oss.nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The correct setting for the RGMII ports on LS1043ARDB is to
enable delay on both Rx and Tx so the interface mode used must
be PHY_INTERFACE_MODE_RGMII_ID.

Since commit 1b3047b5 ("net: phy: realtek: add support for
configuring the RX delay on RTL8211F") the Realtek 8211F PHY driver
has control over the RGMII RX delay and it is disabling it for
RGMII_TXID. The LS1043ARDB uses two such PHYs in RGMII_ID mode but
in the device tree the mode was described as "rgmii_txid".
This issue was not apparent at the time as the PHY driver took the
same action for RGMII_TXID and RGMII_ID back then but it became
visible (RX no longer working) after the above patch.

Changing the phy-connection-type to "rgmii-id" to address the issue.

Fixes: bf02f2ff ("arm64: dts: add LS1043A DPAA FMan support")
Signed-off-by: Madalin Bucur <madalin.bucur@oss.nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Treat all internal delay variants the same as RGMII.
Signed-off-by: Madalin Bucur <madalin.bucur@oss.nxp.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

Michal Kubecek says:

====================
ethtool: fail with error if request has unknown flags

Jakub Kicinski pointed out that if unrecognized flags are set in netlink
header request, kernel shoud fail with an error rather than silently
ignore them so that we have more freedom in future flags semantics.

To help userspace with handling such errors, inform the client which
flags are supported by kernel. For that purpose, we need to allow
passing cookies as part of extack also in case of error (they can be
only passed on success now).
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

As pointed out by Jakub Kicinski, we ethtool netlink code should respond
with an error if request head has flags set which are not recognized by
kernel, either as a mistake or because it expects functionality introduced
in later kernel versions.

To avoid unnecessary roundtrips, use extack cookie to provide the
information about supported request flags.
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

Similar to existing nl_set_extack_cookie_u64(), add new helper
nl_set_extack_cookie_u32() which sets extack cookie to a u32 value.
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

Commit ba0dc5f6 ("netlink: allow sending extended ACK with cookie on
success") introduced a cookie which can be sent to userspace as part of
extended ack message in the form of NLMSGERR_ATTR_COOKIE attribute.
Currently the cookie is ignored if error code is non-zero but there is
no technical reason for such limitation and it can be useful to provide
machine parseable information as part of an error message.

Include NLMSGERR_ATTR_COOKIE whenever the cookie has been set,
regardless of error code.
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

route4_change() allocates a new filter and copies values from
the old one. After the new filter is inserted into the hash
table, the old filter should be removed and freed, as the final
step of the update.

However, the current code mistakenly removes the new one. This
looks apparently wrong to me, and it causes double "free" and
use-after-free too, as reported by syzbot.

Reported-and-tested-by: syzbot+f9b32aaacd60305d9687@syzkaller.appspotmail.com
Reported-and-tested-by: syzbot+2f8c233f131943d6056d@syzkaller.appspotmail.com
Reported-and-tested-by: syzbot+9c2df9fd5e9445b74e01@syzkaller.appspotmail.com
Fixes: 1109c005 ("net: sched: RCU cls_route")
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Cc: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Taehee Yoo says:

====================
hsr: fix several bugs in generic netlink callback

This patchset is to fix several bugs they are related in
generic netlink callback in hsr module.

1. The first patch is to add missing rcu_read_lock() in
hsr_get_node_{list/status}().
The hsr_get_node_{list/status}() are not protected by RTNL because
they are callback functions of generic netlink.
But it calls __dev_get_by_index() without acquiring RTNL.
So, it would use unsafe data.

2. The second patch is to avoid failure of hsr_get_node_list().
hsr_get_node_list() is a callback of generic netlink and
it is used to get node information in userspace.
But, if there are so many nodes, it fails because of buffer size.
So, in this patch, restart routine is added.

3. The third patch is to set .netnsok flag to true.
If .netnsok flag is false, non-init_net namespace is not allowed to
operate generic netlink operations.
So, currently, non-init_net namespace has no way to get node information
because .netnsok is false in the current hsr code.

Change log:
v1->v2:
 - Preserve reverse christmas tree variable ordering in the second patch.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

The hsr module has been supporting the list and status command.
(HSR_C_GET_NODE_LIST and HSR_C_GET_NODE_STATUS)
These commands send node information to the user-space via generic netlink.
But, in the non-init_net namespace, these commands are not allowed
because .netnsok flag is false.
So, there is no way to get node information in the non-init_net namespace.

Fixes: f421436a ("net/hsr: Add support for the High-availability Seamless Redundancy protocol (HSRv0)")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The hsr_get_node_list() is to send node addresses to the userspace.
If there are so many nodes, it could fail because of buffer size.
In order to avoid this failure, the restart routine is added.

Fixes: f421436a ("net/hsr: Add support for the High-availability Seamless Redundancy protocol (HSRv0)")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

hsr_get_node_{list/status}() are not under rtnl_lock() because
they are callback functions of generic netlink.
But they use __dev_get_by_index() without rtnl_lock().
So, it would use unsafe data.
In order to fix it, rcu_read_lock() and dev_get_by_index_rcu()
are used instead of __dev_get_by_index().

Fixes: f421436a ("net/hsr: Add support for the High-availability Seamless Redundancy protocol (HSRv0)")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Takashi Iwai says:

====================
net: Use scnprintf() for avoiding potential buffer overflow

here is a respin of trivial patch series just to convert suspicious
snprintf() usages with the more safer one, scnprintf().

v1->v2: Align the remaining lines to the open parenthesis
        Excluded i40e patch that was already queued
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Since snprintf() returns the would-be-output size instead of the
actual output size, the succeeding calls may go beyond the given
buffer limit.  Fix it by replacing with scnprintf().

Cc: "David S . Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Since snprintf() returns the would-be-output size instead of the
actual output size, the succeeding calls may go beyond the given
buffer limit.  Fix it by replacing with scnprintf().

Cc: "David S . Miller" <davem@davemloft.net>
Cc: Edward Cree <ecree@solarflare.com>
Cc: Martin Habets <mhabets@solarflare.com>
Cc: Solarflare linux maintainers <linux-net-drivers@solarflare.com>
Cc: netdev@vger.kernel.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: David S. Miller <davem@davemloft.net>