<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux.git/net/bpfilter, branch v4.19-rc2</title>
<subtitle>Linux kernel source tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/'/>
<entry>
<title>Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next</title>
<updated>2018-08-15T22:04:25+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2018-08-15T22:04:25+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=9a76aba02a37718242d7cdc294f0a3901928aa57'/>
<id>9a76aba02a37718242d7cdc294f0a3901928aa57</id>
<content type='text'>
Pull networking updates from David Miller:
 "Highlights:

   - Gustavo A. R. Silva keeps working on the implicit switch fallthru
     changes.

   - Support 802.11ax High-Efficiency wireless in cfg80211 et al, From
     Luca Coelho.

   - Re-enable ASPM in r8169, from Kai-Heng Feng.

   - Add virtual XFRM interfaces, which avoids all of the limitations of
     existing IPSEC tunnels. From Steffen Klassert.

   - Convert GRO over to use a hash table, so that when we have many
     flows active we don't traverse a long list during accumluation.

   - Many new self tests for routing, TC, tunnels, etc. Too many
     contributors to mention them all, but I'm really happy to keep
     seeing this stuff.

   - Hardware timestamping support for dpaa_eth/fsl-fman from Yangbo Lu.

   - Lots of cleanups and fixes in L2TP code from Guillaume Nault.

   - Add IPSEC offload support to netdevsim, from Shannon Nelson.

   - Add support for slotting with non-uniform distribution to netem
     packet scheduler, from Yousuk Seung.

   - Add UDP GSO support to mlx5e, from Boris Pismenny.

   - Support offloading of Team LAG in NFP, from John Hurley.

   - Allow to configure TX queue selection based upon RX queue, from
     Amritha Nambiar.

   - Support ethtool ring size configuration in aquantia, from Anton
     Mikaev.

   - Support DSCP and flowlabel per-transport in SCTP, from Xin Long.

   - Support list based batching and stack traversal of SKBs, this is
     very exciting work. From Edward Cree.

   - Busyloop optimizations in vhost_net, from Toshiaki Makita.

   - Introduce the ETF qdisc, which allows time based transmissions. IGB
     can offload this in hardware. From Vinicius Costa Gomes.

   - Add parameter support to devlink, from Moshe Shemesh.

   - Several multiplication and division optimizations for BPF JIT in
     nfp driver, from Jiong Wang.

   - Lots of prepatory work to make more of the packet scheduler layer
     lockless, when possible, from Vlad Buslov.

   - Add ACK filter and NAT awareness to sch_cake packet scheduler, from
     Toke Høiland-Jørgensen.

   - Support regions and region snapshots in devlink, from Alex Vesker.

   - Allow to attach XDP programs to both HW and SW at the same time on
     a given device, with initial support in nfp. From Jakub Kicinski.

   - Add TLS RX offload and support in mlx5, from Ilya Lesokhin.

   - Use PHYLIB in r8169 driver, from Heiner Kallweit.

   - All sorts of changes to support Spectrum 2 in mlxsw driver, from
     Ido Schimmel.

   - PTP support in mv88e6xxx DSA driver, from Andrew Lunn.

   - Make TCP_USER_TIMEOUT socket option more accurate, from Jon
     Maxwell.

   - Support for templates in packet scheduler classifier, from Jiri
     Pirko.

   - IPV6 support in RDS, from Ka-Cheong Poon.

   - Native tproxy support in nf_tables, from Máté Eckl.

   - Maintain IP fragment queue in an rbtree, but optimize properly for
     in-order frags. From Peter Oskolkov.

   - Improvde handling of ACKs on hole repairs, from Yuchung Cheng"

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next: (1996 commits)
  bpf: test: fix spelling mistake "REUSEEPORT" -&gt; "REUSEPORT"
  hv/netvsc: Fix NULL dereference at single queue mode fallback
  net: filter: mark expected switch fall-through
  xen-netfront: fix warn message as irq device name has '/'
  cxgb4: Add new T5 PCI device ids 0x50af and 0x50b0
  net: dsa: mv88e6xxx: missing unlock on error path
  rds: fix building with IPV6=m
  inet/connection_sock: prefer _THIS_IP_ to current_text_addr
  net: dsa: mv88e6xxx: bitwise vs logical bug
  net: sock_diag: Fix spectre v1 gadget in __sock_diag_cmd()
  ieee802154: hwsim: using right kind of iteration
  net: hns3: Add vlan filter setting by ethtool command -K
  net: hns3: Set tx ring' tc info when netdev is up
  net: hns3: Remove tx ring BD len register in hns3_enet
  net: hns3: Fix desc num set to default when setting channel
  net: hns3: Fix for phy link issue when using marvell phy driver
  net: hns3: Fix for information of phydev lost problem when down/up
  net: hns3: Fix for command format parsing error in hclge_is_all_function_id_zero
  net: hns3: Add support for serdes loopback selftest
  bnxt_en: take coredump_record structure off stack
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull networking updates from David Miller:
 "Highlights:

   - Gustavo A. R. Silva keeps working on the implicit switch fallthru
     changes.

   - Support 802.11ax High-Efficiency wireless in cfg80211 et al, From
     Luca Coelho.

   - Re-enable ASPM in r8169, from Kai-Heng Feng.

   - Add virtual XFRM interfaces, which avoids all of the limitations of
     existing IPSEC tunnels. From Steffen Klassert.

   - Convert GRO over to use a hash table, so that when we have many
     flows active we don't traverse a long list during accumluation.

   - Many new self tests for routing, TC, tunnels, etc. Too many
     contributors to mention them all, but I'm really happy to keep
     seeing this stuff.

   - Hardware timestamping support for dpaa_eth/fsl-fman from Yangbo Lu.

   - Lots of cleanups and fixes in L2TP code from Guillaume Nault.

   - Add IPSEC offload support to netdevsim, from Shannon Nelson.

   - Add support for slotting with non-uniform distribution to netem
     packet scheduler, from Yousuk Seung.

   - Add UDP GSO support to mlx5e, from Boris Pismenny.

   - Support offloading of Team LAG in NFP, from John Hurley.

   - Allow to configure TX queue selection based upon RX queue, from
     Amritha Nambiar.

   - Support ethtool ring size configuration in aquantia, from Anton
     Mikaev.

   - Support DSCP and flowlabel per-transport in SCTP, from Xin Long.

   - Support list based batching and stack traversal of SKBs, this is
     very exciting work. From Edward Cree.

   - Busyloop optimizations in vhost_net, from Toshiaki Makita.

   - Introduce the ETF qdisc, which allows time based transmissions. IGB
     can offload this in hardware. From Vinicius Costa Gomes.

   - Add parameter support to devlink, from Moshe Shemesh.

   - Several multiplication and division optimizations for BPF JIT in
     nfp driver, from Jiong Wang.

   - Lots of prepatory work to make more of the packet scheduler layer
     lockless, when possible, from Vlad Buslov.

   - Add ACK filter and NAT awareness to sch_cake packet scheduler, from
     Toke Høiland-Jørgensen.

   - Support regions and region snapshots in devlink, from Alex Vesker.

   - Allow to attach XDP programs to both HW and SW at the same time on
     a given device, with initial support in nfp. From Jakub Kicinski.

   - Add TLS RX offload and support in mlx5, from Ilya Lesokhin.

   - Use PHYLIB in r8169 driver, from Heiner Kallweit.

   - All sorts of changes to support Spectrum 2 in mlxsw driver, from
     Ido Schimmel.

   - PTP support in mv88e6xxx DSA driver, from Andrew Lunn.

   - Make TCP_USER_TIMEOUT socket option more accurate, from Jon
     Maxwell.

   - Support for templates in packet scheduler classifier, from Jiri
     Pirko.

   - IPV6 support in RDS, from Ka-Cheong Poon.

   - Native tproxy support in nf_tables, from Máté Eckl.

   - Maintain IP fragment queue in an rbtree, but optimize properly for
     in-order frags. From Peter Oskolkov.

   - Improvde handling of ACKs on hole repairs, from Yuchung Cheng"

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next: (1996 commits)
  bpf: test: fix spelling mistake "REUSEEPORT" -&gt; "REUSEPORT"
  hv/netvsc: Fix NULL dereference at single queue mode fallback
  net: filter: mark expected switch fall-through
  xen-netfront: fix warn message as irq device name has '/'
  cxgb4: Add new T5 PCI device ids 0x50af and 0x50b0
  net: dsa: mv88e6xxx: missing unlock on error path
  rds: fix building with IPV6=m
  inet/connection_sock: prefer _THIS_IP_ to current_text_addr
  net: dsa: mv88e6xxx: bitwise vs logical bug
  net: sock_diag: Fix spectre v1 gadget in __sock_diag_cmd()
  ieee802154: hwsim: using right kind of iteration
  net: hns3: Add vlan filter setting by ethtool command -K
  net: hns3: Set tx ring' tc info when netdev is up
  net: hns3: Remove tx ring BD len register in hns3_enet
  net: hns3: Fix desc num set to default when setting channel
  net: hns3: Fix for phy link issue when using marvell phy driver
  net: hns3: Fix for information of phydev lost problem when down/up
  net: hns3: Fix for command format parsing error in hclge_is_all_function_id_zero
  net: hns3: Add support for serdes loopback selftest
  bnxt_en: take coredump_record structure off stack
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>bpfilter: remove trailing newline</title>
<updated>2018-07-24T21:10:42+00:00</updated>
<author>
<name>Stephen Hemminger</name>
<email>stephen@networkplumber.org</email>
</author>
<published>2018-07-24T19:29:16+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=a17922def7ca6dba9f40b09a8b36f9cbe3b8bbf3'/>
<id>a17922def7ca6dba9f40b09a8b36f9cbe3b8bbf3</id>
<content type='text'>
Signed-off-by: Stephen Hemminger &lt;stephen@networkplumber.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Signed-off-by: Stephen Hemminger &lt;stephen@networkplumber.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>kbuild: Rename HOSTLDFLAGS to KBUILD_HOSTLDFLAGS</title>
<updated>2018-07-17T16:18:05+00:00</updated>
<author>
<name>Laura Abbott</name>
<email>labbott@redhat.com</email>
</author>
<published>2018-07-10T00:46:00+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=b90a368000abe5e015e0b045ca2ff7c2173b94c0'/>
<id>b90a368000abe5e015e0b045ca2ff7c2173b94c0</id>
<content type='text'>
In preparation for enabling command line LDFLAGS, re-name HOSTLDFLAGS
to KBUILD_HOSTLDFLAGS as the internal use only flags. This should not
have any visible effects.

Signed-off-by: Laura Abbott &lt;labbott@redhat.com&gt;
Signed-off-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
In preparation for enabling command line LDFLAGS, re-name HOSTLDFLAGS
to KBUILD_HOSTLDFLAGS as the internal use only flags. This should not
have any visible effects.

Signed-off-by: Laura Abbott &lt;labbott@redhat.com&gt;
Signed-off-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>kbuild: Rename HOSTCFLAGS to KBUILD_HOSTCFLAGS</title>
<updated>2018-07-17T16:18:05+00:00</updated>
<author>
<name>Laura Abbott</name>
<email>labbott@redhat.com</email>
</author>
<published>2018-07-10T00:45:58+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=96f14fe738b69dd97a33efe3cc8ab330af5fd1f1'/>
<id>96f14fe738b69dd97a33efe3cc8ab330af5fd1f1</id>
<content type='text'>
In preparation for enabling command line CFLAGS, re-name HOSTCFLAGS to
KBUILD_HOSTCFLAGS as the internal use only flags. This should not have
any visible effects.

Signed-off-by: Laura Abbott &lt;labbott@redhat.com&gt;
Signed-off-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
In preparation for enabling command line CFLAGS, re-name HOSTCFLAGS to
KBUILD_HOSTCFLAGS as the internal use only flags. This should not have
any visible effects.

Signed-off-by: Laura Abbott &lt;labbott@redhat.com&gt;
Signed-off-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>bpfilter: include bpfilter_umh in assembly instead of using objcopy</title>
<updated>2018-06-28T12:39:16+00:00</updated>
<author>
<name>Masahiro Yamada</name>
<email>yamada.masahiro@socionext.com</email>
</author>
<published>2018-06-27T03:13:48+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=8e75887d321d102200abf3a9fa621e2c10ff4cc5'/>
<id>8e75887d321d102200abf3a9fa621e2c10ff4cc5</id>
<content type='text'>
What we want here is to embed a user-space program into the kernel.
Instead of the complex ELF magic, let's simply wrap it in the assembly
with the '.incbin' directive.

Signed-off-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
What we want here is to embed a user-space program into the kernel.
Instead of the complex ELF magic, let's simply wrap it in the assembly
with the '.incbin' directive.

Signed-off-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>bpfilter: check compiler capability in Kconfig</title>
<updated>2018-06-28T04:36:39+00:00</updated>
<author>
<name>Masahiro Yamada</name>
<email>yamada.masahiro@socionext.com</email>
</author>
<published>2018-06-26T03:55:35+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=88e85a7daf8e21f2d6cb054374d480c540725cde'/>
<id>88e85a7daf8e21f2d6cb054374d480c540725cde</id>
<content type='text'>
With the brand-new syntax extension of Kconfig, we can directly
check the compiler capability in the configuration phase.

If the cc-can-link.sh fails, the BPFILTER_UMH is automatically
hidden by the dependency.

I also deleted 'default n', which is no-op.

Signed-off-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
Acked-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
Acked-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
With the brand-new syntax extension of Kconfig, we can directly
check the compiler capability in the configuration phase.

If the cc-can-link.sh fails, the BPFILTER_UMH is automatically
hidden by the dependency.

I also deleted 'default n', which is no-op.

Signed-off-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
Acked-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
Acked-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>bpfilter: fix user mode helper cross compilation</title>
<updated>2018-06-21T00:19:19+00:00</updated>
<author>
<name>Matteo Croce</name>
<email>mcroce@redhat.com</email>
</author>
<published>2018-06-20T14:04:34+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=c24fb5e68ebfd485ecaa8b5d40cb4721a1d137ee'/>
<id>c24fb5e68ebfd485ecaa8b5d40cb4721a1d137ee</id>
<content type='text'>
Use $(OBJDUMP) instead of literal 'objdump' to avoid
using host toolchain when cross compiling.

Fixes: 421780fd4983 ("bpfilter: fix build error")
Signed-off-by: Matteo Croce &lt;mcroce@redhat.com&gt;
Reported-by: Stefano Brivio &lt;sbrivio@redhat.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Use $(OBJDUMP) instead of literal 'objdump' to avoid
using host toolchain when cross compiling.

Fixes: 421780fd4983 ("bpfilter: fix build error")
Signed-off-by: Matteo Croce &lt;mcroce@redhat.com&gt;
Reported-by: Stefano Brivio &lt;sbrivio@redhat.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>bpfilter: ignore binary files</title>
<updated>2018-06-20T00:07:46+00:00</updated>
<author>
<name>Matteo Croce</name>
<email>mcroce@redhat.com</email>
</author>
<published>2018-06-19T15:21:36+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=8b26a06ad4f2a12425f1f63a0ee57f42961dfd1e'/>
<id>8b26a06ad4f2a12425f1f63a0ee57f42961dfd1e</id>
<content type='text'>
net/bpfilter/bpfilter_umh is a binary file generated when bpfilter is
enabled, add it to .gitignore to avoid committing it.

Fixes: d2ba09c17a064 ("net: add skeleton of bpfilter kernel module")
Signed-off-by: Matteo Croce &lt;mcroce@redhat.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
net/bpfilter/bpfilter_umh is a binary file generated when bpfilter is
enabled, add it to .gitignore to avoid committing it.

Fixes: d2ba09c17a064 ("net: add skeleton of bpfilter kernel module")
Signed-off-by: Matteo Croce &lt;mcroce@redhat.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>bpfilter: fix build error</title>
<updated>2018-06-20T00:07:46+00:00</updated>
<author>
<name>Matteo Croce</name>
<email>mcroce@redhat.com</email>
</author>
<published>2018-06-19T15:16:20+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=421780fd498399235b044638e85b352d6da20b6a'/>
<id>421780fd498399235b044638e85b352d6da20b6a</id>
<content type='text'>
bpfilter Makefile assumes that the system locale is en_US, and the
parsing of objdump output fails.
Set LC_ALL=C and, while at it, rewrite the objdump parsing so it spawns
only 2 processes instead of 7.

Fixes: d2ba09c17a064 ("net: add skeleton of bpfilter kernel module")
Signed-off-by: Matteo Croce &lt;mcroce@redhat.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
bpfilter Makefile assumes that the system locale is en_US, and the
parsing of objdump output fails.
Set LC_ALL=C and, while at it, rewrite the objdump parsing so it spawns
only 2 processes instead of 7.

Fixes: d2ba09c17a064 ("net: add skeleton of bpfilter kernel module")
Signed-off-by: Matteo Croce &lt;mcroce@redhat.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>bpfilter: fix race in pipe access</title>
<updated>2018-06-08T00:07:28+00:00</updated>
<author>
<name>Alexei Starovoitov</name>
<email>ast@kernel.org</email>
</author>
<published>2018-06-07T22:31:14+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=66e58e0ef80a56a1d7857b6ce121141563cdd93e'/>
<id>66e58e0ef80a56a1d7857b6ce121141563cdd93e</id>
<content type='text'>
syzbot reported the following crash
[  338.293946] bpfilter: read fail -512
[  338.304515] kasan: GPF could be caused by NULL-ptr deref or user memory access
[  338.311863] general protection fault: 0000 [#1] SMP KASAN
[  338.344360] RIP: 0010:__vfs_write+0x4a6/0x960
[  338.426363] Call Trace:
[  338.456967]  __kernel_write+0x10c/0x380
[  338.460928]  __bpfilter_process_sockopt+0x1d8/0x35b
[  338.487103]  bpfilter_mbox_request+0x4d/0xb0
[  338.491492]  bpfilter_ip_get_sockopt+0x6b/0x90

This can happen when multiple cpus trying to talk to user mode process
via bpfilter_mbox_request(). One cpu grabs the mutex while another goes to
sleep on the same mutex. Then former cpu sees that umh pipe is down and
shuts down the pipes. Later cpu finally acquires the mutex and crashes
on freed pipe.
Fix the race by using info.pid as an indicator that umh and pipes are healthy
and check it after acquiring the mutex.

Fixes: d2ba09c17a06 ("net: add skeleton of bpfilter kernel module")
Reported-by: syzbot+7ade6c94abb2774c0fee@syzkaller.appspotmail.com
Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
syzbot reported the following crash
[  338.293946] bpfilter: read fail -512
[  338.304515] kasan: GPF could be caused by NULL-ptr deref or user memory access
[  338.311863] general protection fault: 0000 [#1] SMP KASAN
[  338.344360] RIP: 0010:__vfs_write+0x4a6/0x960
[  338.426363] Call Trace:
[  338.456967]  __kernel_write+0x10c/0x380
[  338.460928]  __bpfilter_process_sockopt+0x1d8/0x35b
[  338.487103]  bpfilter_mbox_request+0x4d/0xb0
[  338.491492]  bpfilter_ip_get_sockopt+0x6b/0x90

This can happen when multiple cpus trying to talk to user mode process
via bpfilter_mbox_request(). One cpu grabs the mutex while another goes to
sleep on the same mutex. Then former cpu sees that umh pipe is down and
shuts down the pipes. Later cpu finally acquires the mutex and crashes
on freed pipe.
Fix the race by using info.pid as an indicator that umh and pipes are healthy
and check it after acquiring the mutex.

Fixes: d2ba09c17a06 ("net: add skeleton of bpfilter kernel module")
Reported-by: syzbot+7ade6c94abb2774c0fee@syzkaller.appspotmail.com
Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
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