linux.git/net, branch v4.19.233 Clone of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git net: dcb: disable softirqs in dcbnl_flush_dev() 2022-03-08T18:04:10+00:00 Vladimir Oltean vladimir.oltean@nxp.com 2022-03-02T19:39:39+00:00 a6a21ff5cfc21be757e4b825acf873eabc3bb4e2 commit 10b6bb62ae1a49ee818fc479cf57b8900176773e upstream. Ido Schimmel points out that since commit 52cff74eef5d ("dcbnl : Disable software interrupts before taking dcb_lock"), the DCB API can be called by drivers from softirq context. One such in-tree example is the chelsio cxgb4 driver: dcb_rpl -> cxgb4_dcb_handle_fw_update -> dcb_ieee_setapp If the firmware for this driver happened to send an event which resulted in a call to dcb_ieee_setapp() at the exact same time as another DCB-enabled interface was unregistering on the same CPU, the softirq would deadlock, because the interrupted process was already holding the dcb_lock in dcbnl_flush_dev(). Fix this unlikely event by using spin_lock_bh() in dcbnl_flush_dev() as in the rest of the dcbnl code. Fixes: 91b0383fef06 ("net: dcb: flush lingering app table entries for unregistered devices") Reported-by: Ido Schimmel <idosch@idosch.org> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> Link: https://lore.kernel.org/r/20220302193939.1368823-1-vladimir.oltean@nxp.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 10b6bb62ae1a49ee818fc479cf57b8900176773e upstream.

Ido Schimmel points out that since commit 52cff74eef5d ("dcbnl : Disable
software interrupts before taking dcb_lock"), the DCB API can be called
by drivers from softirq context.

One such in-tree example is the chelsio cxgb4 driver:
dcb_rpl
-> cxgb4_dcb_handle_fw_update
   -> dcb_ieee_setapp

If the firmware for this driver happened to send an event which resulted
in a call to dcb_ieee_setapp() at the exact same time as another
DCB-enabled interface was unregistering on the same CPU, the softirq
would deadlock, because the interrupted process was already holding the
dcb_lock in dcbnl_flush_dev().

Fix this unlikely event by using spin_lock_bh() in dcbnl_flush_dev() as
in the rest of the dcbnl code.

Fixes: 91b0383fef06 ("net: dcb: flush lingering app table entries for unregistered devices")
Reported-by: Ido Schimmel <idosch@idosch.org>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20220302193939.1368823-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
nl80211: Handle nla_memdup failures in handle_nan_filter 2022-03-08T18:04:09+00:00 Jiasheng Jiang jiasheng@iscas.ac.cn 2022-03-01T10:00:20+00:00 19e164396ba9f1f11e35cfc575c07b23a83ee5b9 [ Upstream commit 6ad27f522cb3b210476daf63ce6ddb6568c0508b ] As there's potential for failure of the nla_memdup(), check the return value. Fixes: a442b761b24b ("cfg80211: add add_nan_func / del_nan_func") Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn> Link: https://lore.kernel.org/r/20220301100020.3801187-1-jiasheng@iscas.ac.cn Signed-off-by: Johannes Berg <johannes.berg@intel.com> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 6ad27f522cb3b210476daf63ce6ddb6568c0508b ]

As there's potential for failure of the nla_memdup(),
check the return value.

Fixes: a442b761b24b ("cfg80211: add add_nan_func / del_nan_func")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Link: https://lore.kernel.org/r/20220301100020.3801187-1-jiasheng@iscas.ac.cn
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
mac80211: fix forwarded mesh frames AC & queue selection 2022-03-08T18:04:08+00:00 Nicolas Escande nico.escande@gmail.com 2022-02-14T17:32:14+00:00 dd13b055d24d67ae342c5775cbc8454514a7cee9 commit 859ae7018316daa4adbc496012dcbbb458d7e510 upstream. There are two problems with the current code that have been highlighted with the AQL feature that is now enbaled by default. First problem is in ieee80211_rx_h_mesh_fwding(), ieee80211_select_queue_80211() is used on received packets to choose the sending AC queue of the forwarding packet although this function should only be called on TX packet (it uses ieee80211_tx_info). This ends with forwarded mesh packets been sent on unrelated random AC queue. To fix that, AC queue can directly be infered from skb->priority which has been extracted from QOS info (see ieee80211_parse_qos()). Second problem is the value of queue_mapping set on forwarded mesh frames via skb_set_queue_mapping() is not the AC of the packet but a hardware queue index. This may or may not work depending on AC to HW queue mapping which is driver specific. Both of these issues lead to improper AC selection while forwarding mesh packets but more importantly due to improper airtime accounting (which is done on a per STA, per AC basis) caused traffic stall with the introduction of AQL. Fixes: cf44012810cc ("mac80211: fix unnecessary frame drops in mesh fwding") Fixes: d3c1597b8d1b ("mac80211: fix forwarded mesh frame queue mapping") Co-developed-by: Remi Pommarel <repk@triplefau.lt> Signed-off-by: Remi Pommarel <repk@triplefau.lt> Signed-off-by: Nicolas Escande <nico.escande@gmail.com> Link: https://lore.kernel.org/r/20220214173214.368862-1-nico.escande@gmail.com Signed-off-by: Johannes Berg <johannes.berg@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 859ae7018316daa4adbc496012dcbbb458d7e510 upstream.

There are two problems with the current code that have been highlighted
with the AQL feature that is now enbaled by default.

First problem is in ieee80211_rx_h_mesh_fwding(),
ieee80211_select_queue_80211() is used on received packets to choose
the sending AC queue of the forwarding packet although this function
should only be called on TX packet (it uses ieee80211_tx_info).
This ends with forwarded mesh packets been sent on unrelated random AC
queue. To fix that, AC queue can directly be infered from skb->priority
which has been extracted from QOS info (see ieee80211_parse_qos()).

Second problem is the value of queue_mapping set on forwarded mesh
frames via skb_set_queue_mapping() is not the AC of the packet but a
hardware queue index. This may or may not work depending on AC to HW
queue mapping which is driver specific.

Both of these issues lead to improper AC selection while forwarding
mesh packets but more importantly due to improper airtime accounting
(which is done on a per STA, per AC basis) caused traffic stall with
the introduction of AQL.

Fixes: cf44012810cc ("mac80211: fix unnecessary frame drops in mesh fwding")
Fixes: d3c1597b8d1b ("mac80211: fix forwarded mesh frame queue mapping")
Co-developed-by: Remi Pommarel <repk@triplefau.lt>
Signed-off-by: Remi Pommarel <repk@triplefau.lt>
Signed-off-by: Nicolas Escande <nico.escande@gmail.com>
Link: https://lore.kernel.org/r/20220214173214.368862-1-nico.escande@gmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
net/smc: fix unexpected SMC_CLC_DECL_ERR_REGRMB error cause by server 2022-03-08T18:04:08+00:00 D. Wythe alibuda@linux.alibaba.com 2022-03-02T13:25:12+00:00 9b64b0928207be2aabc5e6c71be86d469ebd3256 commit 4940a1fdf31c39f0806ac831cde333134862030b upstream. The problem of SMC_CLC_DECL_ERR_REGRMB on the server is very clear. Based on the fact that whether a new SMC connection can be accepted or not depends on not only the limit of conn nums, but also the available entries of rtoken. Since the rtoken release is trigger by peer, while the conn nums is decrease by local, tons of thing can happen in this time difference. This only thing that needs to be mentioned is that now all connection creations are completely protected by smc_server_lgr_pending lock, it's enough to check only the available entries in rtokens_used_mask. Fixes: cd6851f30386 ("smc: remote memory buffers (RMBs)") Signed-off-by: D. Wythe <alibuda@linux.alibaba.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 4940a1fdf31c39f0806ac831cde333134862030b upstream.

The problem of SMC_CLC_DECL_ERR_REGRMB on the server is very clear.
Based on the fact that whether a new SMC connection can be accepted or
not depends on not only the limit of conn nums, but also the available
entries of rtoken. Since the rtoken release is trigger by peer, while
the conn nums is decrease by local, tons of thing can happen in this
time difference.

This only thing that needs to be mentioned is that now all connection
creations are completely protected by smc_server_lgr_pending lock, it's
enough to check only the available entries in rtokens_used_mask.

Fixes: cd6851f30386 ("smc: remote memory buffers (RMBs)")
Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
net/smc: fix unexpected SMC_CLC_DECL_ERR_REGRMB error generated by client 2022-03-08T18:04:08+00:00 D. Wythe alibuda@linux.alibaba.com 2022-03-02T13:25:11+00:00 e84b216e55ac570f7a137e3bc78c80fc44f6aa2e commit 0537f0a2151375dcf90c1bbfda6a0aaf57164e89 upstream. The main reason for this unexpected SMC_CLC_DECL_ERR_REGRMB in client dues to following execution sequence: Server Conn A: Server Conn B: Client Conn B: smc_lgr_unregister_conn smc_lgr_register_conn smc_clc_send_accept -> smc_rtoken_add smcr_buf_unuse -> Client Conn A: smc_rtoken_delete smc_lgr_unregister_conn() makes current link available to assigned to new incoming connection, while smcr_buf_unuse() has not executed yet, which means that smc_rtoken_add may fail because of insufficient rtoken_entry, reversing their execution order will avoid this problem. Fixes: 3e034725c0d8 ("net/smc: common functions for RMBs and send buffers") Signed-off-by: D. Wythe <alibuda@linux.alibaba.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 0537f0a2151375dcf90c1bbfda6a0aaf57164e89 upstream.

The main reason for this unexpected SMC_CLC_DECL_ERR_REGRMB in client
dues to following execution sequence:

Server Conn A:           Server Conn B:			Client Conn B:

smc_lgr_unregister_conn
                        smc_lgr_register_conn
                        smc_clc_send_accept     ->
                                                        smc_rtoken_add
smcr_buf_unuse
		->		Client Conn A:
				smc_rtoken_delete

smc_lgr_unregister_conn() makes current link available to assigned to new
incoming connection, while smcr_buf_unuse() has not executed yet, which
means that smc_rtoken_add may fail because of insufficient rtoken_entry,
reversing their execution order will avoid this problem.

Fixes: 3e034725c0d8 ("net/smc: common functions for RMBs and send buffers")
Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
net: dcb: flush lingering app table entries for unregistered devices 2022-03-08T18:04:08+00:00 Vladimir Oltean vladimir.oltean@nxp.com 2022-02-24T16:01:54+00:00 155e6abb1d71078ef3a0bf38c4cb3f69b200e9fa commit 91b0383fef06f20b847fa9e4f0e3054ead0b1a1b upstream. If I'm not mistaken (and I don't think I am), the way in which the dcbnl_ops work is that drivers call dcb_ieee_setapp() and this populates the application table with dynamically allocated struct dcb_app_type entries that are kept in the module-global dcb_app_list. However, nobody keeps exact track of these entries, and although dcb_ieee_delapp() is supposed to remove them, nobody does so when the interface goes away (example: driver unbinds from device). So the dcb_app_list will contain lingering entries with an ifindex that no longer matches any device in dcb_app_lookup(). Reclaim the lost memory by listening for the NETDEV_UNREGISTER event and flushing the app table entries of interfaces that are now gone. In fact something like this used to be done as part of the initial commit (blamed below), but it was done in dcbnl_exit() -> dcb_flushapp(), essentially at module_exit time. That became dead code after commit 7a6b6f515f77 ("DCB: fix kconfig option") which essentially merged "tristate config DCB" and "bool config DCBNL" into a single "bool config DCB", so net/dcb/dcbnl.c could not be built as a module anymore. Commit 36b9ad8084bd ("net/dcb: make dcbnl.c explicitly non-modular") recognized this and deleted dcbnl_exit() and dcb_flushapp() altogether, leaving us with the version we have today. Since flushing application table entries can and should be done as soon as the netdevice disappears, fundamentally the commit that is to blame is the one that introduced the design of this API. Fixes: 9ab933ab2cc8 ("dcbnl: add appliction tlv handlers") Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 91b0383fef06f20b847fa9e4f0e3054ead0b1a1b upstream.

If I'm not mistaken (and I don't think I am), the way in which the
dcbnl_ops work is that drivers call dcb_ieee_setapp() and this populates
the application table with dynamically allocated struct dcb_app_type
entries that are kept in the module-global dcb_app_list.

However, nobody keeps exact track of these entries, and although
dcb_ieee_delapp() is supposed to remove them, nobody does so when the
interface goes away (example: driver unbinds from device). So the
dcb_app_list will contain lingering entries with an ifindex that no
longer matches any device in dcb_app_lookup().

Reclaim the lost memory by listening for the NETDEV_UNREGISTER event and
flushing the app table entries of interfaces that are now gone.

In fact something like this used to be done as part of the initial
commit (blamed below), but it was done in dcbnl_exit() -> dcb_flushapp(),
essentially at module_exit time. That became dead code after commit
7a6b6f515f77 ("DCB: fix kconfig option") which essentially merged
"tristate config DCB" and "bool config DCBNL" into a single "bool config
DCB", so net/dcb/dcbnl.c could not be built as a module anymore.

Commit 36b9ad8084bd ("net/dcb: make dcbnl.c explicitly non-modular")
recognized this and deleted dcbnl_exit() and dcb_flushapp() altogether,
leaving us with the version we have today.

Since flushing application table entries can and should be done as soon
as the netdevice disappears, fundamentally the commit that is to blame
is the one that introduced the design of this API.

Fixes: 9ab933ab2cc8 ("dcbnl: add appliction tlv handlers")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
batman-adv: Don't expect inter-netns unique iflink indices 2022-03-08T18:04:08+00:00 Sven Eckelmann sven@narfation.org 2022-02-27T22:23:49+00:00 92a556ef51590bcacfe691124c10d31e12693690 commit 6c1f41afc1dbe59d9d3c8bb0d80b749c119aa334 upstream. The ifindex doesn't have to be unique for multiple network namespaces on the same machine. $ ip netns add test1 $ ip -net test1 link add dummy1 type dummy $ ip netns add test2 $ ip -net test2 link add dummy2 type dummy $ ip -net test1 link show dev dummy1 6: dummy1: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000 link/ether 96:81:55:1e:dd:85 brd ff:ff:ff:ff:ff:ff $ ip -net test2 link show dev dummy2 6: dummy2: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000 link/ether 5a:3c:af:35:07:c3 brd ff:ff:ff:ff:ff:ff But the batman-adv code to walk through the various layers of virtual interfaces uses this assumption because dev_get_iflink handles it internally and doesn't return the actual netns of the iflink. And dev_get_iflink only documents the situation where ifindex == iflink for physical devices. But only checking for dev->netdev_ops->ndo_get_iflink is also not an option because ipoib_get_iflink implements it even when it sometimes returns an iflink != ifindex and sometimes iflink == ifindex. The caller must therefore make sure itself to check both netns and iflink + ifindex for equality. Only when they are equal, a "physical" interface was detected which should stop the traversal. On the other hand, vxcan_get_iflink can also return 0 in case there was currently no valid peer. In this case, it is still necessary to stop. Fixes: b7eddd0b3950 ("batman-adv: prevent using any virtual device created on batman-adv as hard-interface") Fixes: 5ed4a460a1d3 ("batman-adv: additional checks for virtual interfaces on top of WiFi") Reported-by: Sabrina Dubroca <sd@queasysnail.net> Signed-off-by: Sven Eckelmann <sven@narfation.org> Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 6c1f41afc1dbe59d9d3c8bb0d80b749c119aa334 upstream.

The ifindex doesn't have to be unique for multiple network namespaces on
the same machine.

  $ ip netns add test1
  $ ip -net test1 link add dummy1 type dummy
  $ ip netns add test2
  $ ip -net test2 link add dummy2 type dummy

  $ ip -net test1 link show dev dummy1
  6: dummy1: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
      link/ether 96:81:55:1e:dd:85 brd ff:ff:ff:ff:ff:ff
  $ ip -net test2 link show dev dummy2
  6: dummy2: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
      link/ether 5a:3c:af:35:07:c3 brd ff:ff:ff:ff:ff:ff

But the batman-adv code to walk through the various layers of virtual
interfaces uses this assumption because dev_get_iflink handles it
internally and doesn't return the actual netns of the iflink. And
dev_get_iflink only documents the situation where ifindex == iflink for
physical devices.

But only checking for dev->netdev_ops->ndo_get_iflink is also not an option
because ipoib_get_iflink implements it even when it sometimes returns an
iflink != ifindex and sometimes iflink == ifindex. The caller must
therefore make sure itself to check both netns and iflink + ifindex for
equality. Only when they are equal, a "physical" interface was detected
which should stop the traversal. On the other hand, vxcan_get_iflink can
also return 0 in case there was currently no valid peer. In this case, it
is still necessary to stop.

Fixes: b7eddd0b3950 ("batman-adv: prevent using any virtual device created on batman-adv as hard-interface")
Fixes: 5ed4a460a1d3 ("batman-adv: additional checks for virtual interfaces on top of WiFi")
Reported-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
batman-adv: Request iflink once in batadv_get_real_netdevice 2022-03-08T18:04:07+00:00 Sven Eckelmann sven@narfation.org 2022-02-27T23:01:24+00:00 130ec90cb3a20a6635fad5307a47f4c5155b74cc commit 6116ba09423f7d140f0460be6a1644dceaad00da upstream. There is no need to call dev_get_iflink multiple times for the same net_device in batadv_get_real_netdevice. And since some of the ndo_get_iflink callbacks are dynamic (for example via RCUs like in vxcan_get_iflink), it could easily happen that the returned values are not stable. The pre-checks before __dev_get_by_index are then of course bogus. Fixes: 5ed4a460a1d3 ("batman-adv: additional checks for virtual interfaces on top of WiFi") Signed-off-by: Sven Eckelmann <sven@narfation.org> Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 6116ba09423f7d140f0460be6a1644dceaad00da upstream.

There is no need to call dev_get_iflink multiple times for the same
net_device in batadv_get_real_netdevice. And since some of the
ndo_get_iflink callbacks are dynamic (for example via RCUs like in
vxcan_get_iflink), it could easily happen that the returned values are not
stable. The pre-checks before __dev_get_by_index are then of course bogus.

Fixes: 5ed4a460a1d3 ("batman-adv: additional checks for virtual interfaces on top of WiFi")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
batman-adv: Request iflink once in batadv-on-batadv check 2022-03-08T18:04:07+00:00 Sven Eckelmann sven@narfation.org 2022-02-27T23:01:24+00:00 86b66abce8ca4c47e7c972ec297a00417499edb4 commit 690bb6fb64f5dc7437317153902573ecad67593d upstream. There is no need to call dev_get_iflink multiple times for the same net_device in batadv_is_on_batman_iface. And since some of the .ndo_get_iflink callbacks are dynamic (for example via RCUs like in vxcan_get_iflink), it could easily happen that the returned values are not stable. The pre-checks before __dev_get_by_index are then of course bogus. Fixes: b7eddd0b3950 ("batman-adv: prevent using any virtual device created on batman-adv as hard-interface") Signed-off-by: Sven Eckelmann <sven@narfation.org> Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 690bb6fb64f5dc7437317153902573ecad67593d upstream.

There is no need to call dev_get_iflink multiple times for the same
net_device in batadv_is_on_batman_iface. And since some of the
.ndo_get_iflink callbacks are dynamic (for example via RCUs like in
vxcan_get_iflink), it could easily happen that the returned values are not
stable. The pre-checks before __dev_get_by_index are then of course bogus.

Fixes: b7eddd0b3950 ("batman-adv: prevent using any virtual device created on batman-adv as hard-interface")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
netfilter: nf_queue: fix possible use-after-free 2022-03-08T18:04:07+00:00 Florian Westphal fw@strlen.de 2022-02-28T05:22:22+00:00 34dc4a6a7f261736ef7183868a5bddad31c7f9e3 commit c3873070247d9e3c7a6b0cf9bf9b45e8018427b1 upstream. Eric Dumazet says: The sock_hold() side seems suspect, because there is no guarantee that sk_refcnt is not already 0. On failure, we cannot queue the packet and need to indicate an error. The packet will be dropped by the caller. v2: split skb prefetch hunk into separate change Fixes: 271b72c7fa82c ("udp: RCU handling for Unicast packets.") Reported-by: Eric Dumazet <eric.dumazet@gmail.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit c3873070247d9e3c7a6b0cf9bf9b45e8018427b1 upstream.

Eric Dumazet says:
  The sock_hold() side seems suspect, because there is no guarantee
  that sk_refcnt is not already 0.

On failure, we cannot queue the packet and need to indicate an
error.  The packet will be dropped by the caller.

v2: split skb prefetch hunk into separate change

Fixes: 271b72c7fa82c ("udp: RCU handling for Unicast packets.")
Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>