<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-stable.git/net/core/dev.c, branch v5.14.2</title>
<subtitle>Linux kernel stable tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/'/>
<entry>
<title>Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf</title>
<updated>2021-07-15T21:39:45+00:00</updated>
<author>
<name>David S. Miller</name>
<email>davem@davemloft.net</email>
</author>
<published>2021-07-15T21:39:45+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=20192d9c9f6ae447c461285c915502ffbddf5696'/>
<id>20192d9c9f6ae447c461285c915502ffbddf5696</id>
<content type='text'>
Andrii Nakryiko says:

====================
pull-request: bpf 2021-07-15

The following pull-request contains BPF updates for your *net* tree.

We've added 9 non-merge commits during the last 5 day(s) which contain
a total of 9 files changed, 37 insertions(+), 15 deletions(-).

The main changes are:

1) Fix NULL pointer dereference in BPF_TEST_RUN for BPF_XDP_DEVMAP and
   BPF_XDP_CPUMAP programs, from Xuan Zhuo.

2) Fix use-after-free of net_device in XDP bpf_link, from Xuan Zhuo.

3) Follow-up fix to subprog poke descriptor use-after-free problem, from
   Daniel Borkmann and John Fastabend.

4) Fix out-of-range array access in s390 BPF JIT backend, from Colin Ian King.

5) Fix memory leak in BPF sockmap, from John Fastabend.

6) Fix for sockmap to prevent proc stats reporting bug, from John Fastabend
   and Jakub Sitnicki.

7) Fix NULL pointer dereference in bpftool, from Tobias Klauser.

8) AF_XDP documentation fixes, from Baruch Siach.
====================

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Andrii Nakryiko says:

====================
pull-request: bpf 2021-07-15

The following pull-request contains BPF updates for your *net* tree.

We've added 9 non-merge commits during the last 5 day(s) which contain
a total of 9 files changed, 37 insertions(+), 15 deletions(-).

The main changes are:

1) Fix NULL pointer dereference in BPF_TEST_RUN for BPF_XDP_DEVMAP and
   BPF_XDP_CPUMAP programs, from Xuan Zhuo.

2) Fix use-after-free of net_device in XDP bpf_link, from Xuan Zhuo.

3) Follow-up fix to subprog poke descriptor use-after-free problem, from
   Daniel Borkmann and John Fastabend.

4) Fix out-of-range array access in s390 BPF JIT backend, from Colin Ian King.

5) Fix memory leak in BPF sockmap, from John Fastabend.

6) Fix for sockmap to prevent proc stats reporting bug, from John Fastabend
   and Jakub Sitnicki.

7) Fix NULL pointer dereference in bpftool, from Tobias Klauser.

8) AF_XDP documentation fixes, from Baruch Siach.
====================

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net_sched: introduce tracepoint trace_qdisc_enqueue()</title>
<updated>2021-07-15T17:32:38+00:00</updated>
<author>
<name>Qitao Xu</name>
<email>qitao.xu@bytedance.com</email>
</author>
<published>2021-07-15T06:03:24+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=70713dddf3d25a02d1952f8c5d2688c986d2f2fb'/>
<id>70713dddf3d25a02d1952f8c5d2688c986d2f2fb</id>
<content type='text'>
Tracepoint trace_qdisc_enqueue() is introduced to trace skb at
the entrance of TC layer on TX side. This is similar to
trace_qdisc_dequeue():

1. For both we only trace successful cases. The failure cases
   can be traced via trace_kfree_skb().

2. They are called at entrance or exit of TC layer, not for each
   -&gt;enqueue() or -&gt;dequeue(). This is intentional, because
   we want to make trace_qdisc_enqueue() symmetric to
   trace_qdisc_dequeue(), which is easier to use.

The return value of qdisc_enqueue() is not interesting here,
we have Qdisc's drop packets in -&gt;dequeue(), it is impossible to
trace them even if we have the return value, the only way to trace
them is tracing kfree_skb().

We only add information we need to trace ring buffer. If any other
information is needed, it is easy to extend it without breaking ABI,
see commit 3dd344ea84e1 ("net: tracepoint: exposing sk_family in all
tcp:tracepoints").

Reviewed-by: Cong Wang &lt;cong.wang@bytedance.com&gt;
Signed-off-by: Qitao Xu &lt;qitao.xu@bytedance.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>
Tracepoint trace_qdisc_enqueue() is introduced to trace skb at
the entrance of TC layer on TX side. This is similar to
trace_qdisc_dequeue():

1. For both we only trace successful cases. The failure cases
   can be traced via trace_kfree_skb().

2. They are called at entrance or exit of TC layer, not for each
   -&gt;enqueue() or -&gt;dequeue(). This is intentional, because
   we want to make trace_qdisc_enqueue() symmetric to
   trace_qdisc_dequeue(), which is easier to use.

The return value of qdisc_enqueue() is not interesting here,
we have Qdisc's drop packets in -&gt;dequeue(), it is impossible to
trace them even if we have the return value, the only way to trace
them is tracing kfree_skb().

We only add information we need to trace ring buffer. If any other
information is needed, it is easy to extend it without breaking ABI,
see commit 3dd344ea84e1 ("net: tracepoint: exposing sk_family in all
tcp:tracepoints").

Reviewed-by: Cong Wang &lt;cong.wang@bytedance.com&gt;
Signed-off-by: Qitao Xu &lt;qitao.xu@bytedance.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>xdp, net: Fix use-after-free in bpf_xdp_link_release</title>
<updated>2021-07-13T15:22:31+00:00</updated>
<author>
<name>Xuan Zhuo</name>
<email>xuanzhuo@linux.alibaba.com</email>
</author>
<published>2021-07-10T03:16:35+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=5acc7d3e8d342858405fbbc671221f676b547ce7'/>
<id>5acc7d3e8d342858405fbbc671221f676b547ce7</id>
<content type='text'>
The problem occurs between dev_get_by_index() and dev_xdp_attach_link().
At this point, dev_xdp_uninstall() is called. Then xdp link will not be
detached automatically when dev is released. But link-&gt;dev already
points to dev, when xdp link is released, dev will still be accessed,
but dev has been released.

dev_get_by_index()        |
link-&gt;dev = dev           |
                          |      rtnl_lock()
                          |      unregister_netdevice_many()
                          |          dev_xdp_uninstall()
                          |      rtnl_unlock()
rtnl_lock();              |
dev_xdp_attach_link()     |
rtnl_unlock();            |
                          |      netdev_run_todo() // dev released
bpf_xdp_link_release()    |
    /* access dev.        |
       use-after-free */  |

[   45.966867] BUG: KASAN: use-after-free in bpf_xdp_link_release+0x3b8/0x3d0
[   45.967619] Read of size 8 at addr ffff00000f9980c8 by task a.out/732
[   45.968297]
[   45.968502] CPU: 1 PID: 732 Comm: a.out Not tainted 5.13.0+ #22
[   45.969222] Hardware name: linux,dummy-virt (DT)
[   45.969795] Call trace:
[   45.970106]  dump_backtrace+0x0/0x4c8
[   45.970564]  show_stack+0x30/0x40
[   45.970981]  dump_stack_lvl+0x120/0x18c
[   45.971470]  print_address_description.constprop.0+0x74/0x30c
[   45.972182]  kasan_report+0x1e8/0x200
[   45.972659]  __asan_report_load8_noabort+0x2c/0x50
[   45.973273]  bpf_xdp_link_release+0x3b8/0x3d0
[   45.973834]  bpf_link_free+0xd0/0x188
[   45.974315]  bpf_link_put+0x1d0/0x218
[   45.974790]  bpf_link_release+0x3c/0x58
[   45.975291]  __fput+0x20c/0x7e8
[   45.975706]  ____fput+0x24/0x30
[   45.976117]  task_work_run+0x104/0x258
[   45.976609]  do_notify_resume+0x894/0xaf8
[   45.977121]  work_pending+0xc/0x328
[   45.977575]
[   45.977775] The buggy address belongs to the page:
[   45.978369] page:fffffc00003e6600 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4f998
[   45.979522] flags: 0x7fffe0000000000(node=0|zone=0|lastcpupid=0x3ffff)
[   45.980349] raw: 07fffe0000000000 fffffc00003e6708 ffff0000dac3c010 0000000000000000
[   45.981309] raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
[   45.982259] page dumped because: kasan: bad access detected
[   45.982948]
[   45.983153] Memory state around the buggy address:
[   45.983753]  ffff00000f997f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[   45.984645]  ffff00000f998000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[   45.985533] &gt;ffff00000f998080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[   45.986419]                                               ^
[   45.987112]  ffff00000f998100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[   45.988006]  ffff00000f998180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[   45.988895] ==================================================================
[   45.989773] Disabling lock debugging due to kernel taint
[   45.990552] Kernel panic - not syncing: panic_on_warn set ...
[   45.991166] CPU: 1 PID: 732 Comm: a.out Tainted: G    B             5.13.0+ #22
[   45.991929] Hardware name: linux,dummy-virt (DT)
[   45.992448] Call trace:
[   45.992753]  dump_backtrace+0x0/0x4c8
[   45.993208]  show_stack+0x30/0x40
[   45.993627]  dump_stack_lvl+0x120/0x18c
[   45.994113]  dump_stack+0x1c/0x34
[   45.994530]  panic+0x3a4/0x7d8
[   45.994930]  end_report+0x194/0x198
[   45.995380]  kasan_report+0x134/0x200
[   45.995850]  __asan_report_load8_noabort+0x2c/0x50
[   45.996453]  bpf_xdp_link_release+0x3b8/0x3d0
[   45.997007]  bpf_link_free+0xd0/0x188
[   45.997474]  bpf_link_put+0x1d0/0x218
[   45.997942]  bpf_link_release+0x3c/0x58
[   45.998429]  __fput+0x20c/0x7e8
[   45.998833]  ____fput+0x24/0x30
[   45.999247]  task_work_run+0x104/0x258
[   45.999731]  do_notify_resume+0x894/0xaf8
[   46.000236]  work_pending+0xc/0x328
[   46.000697] SMP: stopping secondary CPUs
[   46.001226] Dumping ftrace buffer:
[   46.001663]    (ftrace buffer empty)
[   46.002110] Kernel Offset: disabled
[   46.002545] CPU features: 0x00000001,23202c00
[   46.003080] Memory Limit: none

Fixes: aa8d3a716b59db6c ("bpf, xdp: Add bpf_link-based XDP attachment API")
Reported-by: Abaci &lt;abaci@linux.alibaba.com&gt;
Signed-off-by: Xuan Zhuo &lt;xuanzhuo@linux.alibaba.com&gt;
Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Reviewed-by: Dust Li &lt;dust.li@linux.alibaba.com&gt;
Acked-by: Andrii Nakryiko &lt;andrii@kernel.org&gt;
Link: https://lore.kernel.org/bpf/20210710031635.41649-1-xuanzhuo@linux.alibaba.com
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The problem occurs between dev_get_by_index() and dev_xdp_attach_link().
At this point, dev_xdp_uninstall() is called. Then xdp link will not be
detached automatically when dev is released. But link-&gt;dev already
points to dev, when xdp link is released, dev will still be accessed,
but dev has been released.

dev_get_by_index()        |
link-&gt;dev = dev           |
                          |      rtnl_lock()
                          |      unregister_netdevice_many()
                          |          dev_xdp_uninstall()
                          |      rtnl_unlock()
rtnl_lock();              |
dev_xdp_attach_link()     |
rtnl_unlock();            |
                          |      netdev_run_todo() // dev released
bpf_xdp_link_release()    |
    /* access dev.        |
       use-after-free */  |

[   45.966867] BUG: KASAN: use-after-free in bpf_xdp_link_release+0x3b8/0x3d0
[   45.967619] Read of size 8 at addr ffff00000f9980c8 by task a.out/732
[   45.968297]
[   45.968502] CPU: 1 PID: 732 Comm: a.out Not tainted 5.13.0+ #22
[   45.969222] Hardware name: linux,dummy-virt (DT)
[   45.969795] Call trace:
[   45.970106]  dump_backtrace+0x0/0x4c8
[   45.970564]  show_stack+0x30/0x40
[   45.970981]  dump_stack_lvl+0x120/0x18c
[   45.971470]  print_address_description.constprop.0+0x74/0x30c
[   45.972182]  kasan_report+0x1e8/0x200
[   45.972659]  __asan_report_load8_noabort+0x2c/0x50
[   45.973273]  bpf_xdp_link_release+0x3b8/0x3d0
[   45.973834]  bpf_link_free+0xd0/0x188
[   45.974315]  bpf_link_put+0x1d0/0x218
[   45.974790]  bpf_link_release+0x3c/0x58
[   45.975291]  __fput+0x20c/0x7e8
[   45.975706]  ____fput+0x24/0x30
[   45.976117]  task_work_run+0x104/0x258
[   45.976609]  do_notify_resume+0x894/0xaf8
[   45.977121]  work_pending+0xc/0x328
[   45.977575]
[   45.977775] The buggy address belongs to the page:
[   45.978369] page:fffffc00003e6600 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4f998
[   45.979522] flags: 0x7fffe0000000000(node=0|zone=0|lastcpupid=0x3ffff)
[   45.980349] raw: 07fffe0000000000 fffffc00003e6708 ffff0000dac3c010 0000000000000000
[   45.981309] raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
[   45.982259] page dumped because: kasan: bad access detected
[   45.982948]
[   45.983153] Memory state around the buggy address:
[   45.983753]  ffff00000f997f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[   45.984645]  ffff00000f998000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[   45.985533] &gt;ffff00000f998080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[   45.986419]                                               ^
[   45.987112]  ffff00000f998100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[   45.988006]  ffff00000f998180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[   45.988895] ==================================================================
[   45.989773] Disabling lock debugging due to kernel taint
[   45.990552] Kernel panic - not syncing: panic_on_warn set ...
[   45.991166] CPU: 1 PID: 732 Comm: a.out Tainted: G    B             5.13.0+ #22
[   45.991929] Hardware name: linux,dummy-virt (DT)
[   45.992448] Call trace:
[   45.992753]  dump_backtrace+0x0/0x4c8
[   45.993208]  show_stack+0x30/0x40
[   45.993627]  dump_stack_lvl+0x120/0x18c
[   45.994113]  dump_stack+0x1c/0x34
[   45.994530]  panic+0x3a4/0x7d8
[   45.994930]  end_report+0x194/0x198
[   45.995380]  kasan_report+0x134/0x200
[   45.995850]  __asan_report_load8_noabort+0x2c/0x50
[   45.996453]  bpf_xdp_link_release+0x3b8/0x3d0
[   45.997007]  bpf_link_free+0xd0/0x188
[   45.997474]  bpf_link_put+0x1d0/0x218
[   45.997942]  bpf_link_release+0x3c/0x58
[   45.998429]  __fput+0x20c/0x7e8
[   45.998833]  ____fput+0x24/0x30
[   45.999247]  task_work_run+0x104/0x258
[   45.999731]  do_notify_resume+0x894/0xaf8
[   46.000236]  work_pending+0xc/0x328
[   46.000697] SMP: stopping secondary CPUs
[   46.001226] Dumping ftrace buffer:
[   46.001663]    (ftrace buffer empty)
[   46.002110] Kernel Offset: disabled
[   46.002545] CPU features: 0x00000001,23202c00
[   46.003080] Memory Limit: none

Fixes: aa8d3a716b59db6c ("bpf, xdp: Add bpf_link-based XDP attachment API")
Reported-by: Abaci &lt;abaci@linux.alibaba.com&gt;
Signed-off-by: Xuan Zhuo &lt;xuanzhuo@linux.alibaba.com&gt;
Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Reviewed-by: Dust Li &lt;dust.li@linux.alibaba.com&gt;
Acked-by: Andrii Nakryiko &lt;andrii@kernel.org&gt;
Link: https://lore.kernel.org/bpf/20210710031635.41649-1-xuanzhuo@linux.alibaba.com
</pre>
</div>
</content>
</entry>
<entry>
<title>net: do not reuse skbuff allocated from skbuff_fclone_cache in the skb cache</title>
<updated>2021-07-09T18:26:27+00:00</updated>
<author>
<name>Antoine Tenart</name>
<email>atenart@kernel.org</email>
</author>
<published>2021-07-09T16:16:09+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=28b34f01a73435a754956ebae826e728c03ffa38'/>
<id>28b34f01a73435a754956ebae826e728c03ffa38</id>
<content type='text'>
Some socket buffers allocated in the fclone cache (in __alloc_skb) can
end-up in the following path[1]:

napi_skb_finish
  __kfree_skb_defer
    napi_skb_cache_put

The issue is napi_skb_cache_put is not fclone friendly and will put
those skbuff in the skb cache to be reused later, although this cache
only expects skbuff allocated from skbuff_head_cache. When this happens
the skbuff is eventually freed using the wrong origin cache, and we can
see traces similar to:

[ 1223.947534] cache_from_obj: Wrong slab cache. skbuff_head_cache but object is from skbuff_fclone_cache
[ 1223.948895] WARNING: CPU: 3 PID: 0 at mm/slab.h:442 kmem_cache_free+0x251/0x3e0
[ 1223.950211] Modules linked in:
[ 1223.950680] CPU: 3 PID: 0 Comm: swapper/3 Not tainted 5.13.0+ #474
[ 1223.951587] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-3.fc34 04/01/2014
[ 1223.953060] RIP: 0010:kmem_cache_free+0x251/0x3e0

Leading sometimes to other memory related issues.

Fix this by using __kfree_skb for fclone skbuff, similar to what is done
the other place __kfree_skb_defer is called.

[1] At least in setups using veth pairs and tunnels. Building a kernel
    with KASAN we can for example see packets allocated in
    sk_stream_alloc_skb hit the above path and later the issue arises
    when the skbuff is reused.

Fixes: 9243adfc311a ("skbuff: queue NAPI_MERGED_FREE skbs into NAPI cache instead of freeing")
Cc: Alexander Lobakin &lt;alobakin@pm.me&gt;
Signed-off-by: Antoine Tenart &lt;atenart@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>
Some socket buffers allocated in the fclone cache (in __alloc_skb) can
end-up in the following path[1]:

napi_skb_finish
  __kfree_skb_defer
    napi_skb_cache_put

The issue is napi_skb_cache_put is not fclone friendly and will put
those skbuff in the skb cache to be reused later, although this cache
only expects skbuff allocated from skbuff_head_cache. When this happens
the skbuff is eventually freed using the wrong origin cache, and we can
see traces similar to:

[ 1223.947534] cache_from_obj: Wrong slab cache. skbuff_head_cache but object is from skbuff_fclone_cache
[ 1223.948895] WARNING: CPU: 3 PID: 0 at mm/slab.h:442 kmem_cache_free+0x251/0x3e0
[ 1223.950211] Modules linked in:
[ 1223.950680] CPU: 3 PID: 0 Comm: swapper/3 Not tainted 5.13.0+ #474
[ 1223.951587] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-3.fc34 04/01/2014
[ 1223.953060] RIP: 0010:kmem_cache_free+0x251/0x3e0

Leading sometimes to other memory related issues.

Fix this by using __kfree_skb for fclone skbuff, similar to what is done
the other place __kfree_skb_defer is called.

[1] At least in setups using veth pairs and tunnels. Building a kernel
    with KASAN we can for example see packets allocated in
    sk_stream_alloc_skb hit the above path and later the issue arises
    when the skbuff is reused.

Fixes: 9243adfc311a ("skbuff: queue NAPI_MERGED_FREE skbs into NAPI cache instead of freeing")
Cc: Alexander Lobakin &lt;alobakin@pm.me&gt;
Signed-off-by: Antoine Tenart &lt;atenart@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>skbuff: Fix build with SKB extensions disabled</title>
<updated>2021-07-08T07:07:14+00:00</updated>
<author>
<name>Florian Fainelli</name>
<email>f.fainelli@gmail.com</email>
</author>
<published>2021-07-08T04:10:51+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=9615fe36b31d926f1c5107013b772dc226a6a7ca'/>
<id>9615fe36b31d926f1c5107013b772dc226a6a7ca</id>
<content type='text'>
We will fail to build with CONFIG_SKB_EXTENSIONS disabled after
8550ff8d8c75 ("skbuff: Release nfct refcount on napi stolen or re-used
skbs") since there is an unconditionally use of skb_ext_find() without
an appropriate stub. Simply build the code conditionally and properly
guard against both COFNIG_SKB_EXTENSIONS as well as
CONFIG_NET_TC_SKB_EXT being disabled.

Fixes: Fixes: 8550ff8d8c75 ("skbuff: Release nfct refcount on napi stolen or re-used skbs")
Signed-off-by: Florian Fainelli &lt;f.fainelli@gmail.com&gt;
Reviewed-by: Roi Dayan &lt;roid@nvidia.com&gt;
Reviewed-by: Eric Dumazet &lt;edumazet@google.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>
We will fail to build with CONFIG_SKB_EXTENSIONS disabled after
8550ff8d8c75 ("skbuff: Release nfct refcount on napi stolen or re-used
skbs") since there is an unconditionally use of skb_ext_find() without
an appropriate stub. Simply build the code conditionally and properly
guard against both COFNIG_SKB_EXTENSIONS as well as
CONFIG_NET_TC_SKB_EXT being disabled.

Fixes: Fixes: 8550ff8d8c75 ("skbuff: Release nfct refcount on napi stolen or re-used skbs")
Signed-off-by: Florian Fainelli &lt;f.fainelli@gmail.com&gt;
Reviewed-by: Roi Dayan &lt;roid@nvidia.com&gt;
Reviewed-by: Eric Dumazet &lt;edumazet@google.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>skbuff: Release nfct refcount on napi stolen or re-used skbs</title>
<updated>2021-07-06T17:26:29+00:00</updated>
<author>
<name>Paul Blakey</name>
<email>paulb@nvidia.com</email>
</author>
<published>2021-07-05T10:54:51+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=8550ff8d8c75416e984d9c4b082845e57e560984'/>
<id>8550ff8d8c75416e984d9c4b082845e57e560984</id>
<content type='text'>
When multiple SKBs are merged to a new skb under napi GRO,
or SKB is re-used by napi, if nfct was set for them in the
driver, it will not be released while freeing their stolen
head state or on re-use.

Release nfct on napi's stolen or re-used SKBs, and
in gro_list_prepare, check conntrack metadata diff.

Fixes: 5c6b94604744 ("net/mlx5e: CT: Handle misses after executing CT action")
Reviewed-by: Roi Dayan &lt;roid@nvidia.com&gt;
Signed-off-by: Paul Blakey &lt;paulb@nvidia.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>
When multiple SKBs are merged to a new skb under napi GRO,
or SKB is re-used by napi, if nfct was set for them in the
driver, it will not be released while freeing their stolen
head state or on re-use.

Release nfct on napi's stolen or re-used SKBs, and
in gro_list_prepare, check conntrack metadata diff.

Fixes: 5c6b94604744 ("net/mlx5e: CT: Handle misses after executing CT action")
Reviewed-by: Roi Dayan &lt;roid@nvidia.com&gt;
Signed-off-by: Paul Blakey &lt;paulb@nvidia.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'net-next-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next</title>
<updated>2021-06-30T22:51:09+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2021-06-30T22:51:09+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=dbe69e43372212527abf48609aba7fc39a6daa27'/>
<id>dbe69e43372212527abf48609aba7fc39a6daa27</id>
<content type='text'>
Pull networking updates from Jakub Kicinski:
 "Core:

   - BPF:
      - add syscall program type and libbpf support for generating
        instructions and bindings for in-kernel BPF loaders (BPF loaders
        for BPF), this is a stepping stone for signed BPF programs
      - infrastructure to migrate TCP child sockets from one listener to
        another in the same reuseport group/map to improve flexibility
        of service hand-off/restart
      - add broadcast support to XDP redirect

   - allow bypass of the lockless qdisc to improving performance (for
     pktgen: +23% with one thread, +44% with 2 threads)

   - add a simpler version of "DO_ONCE()" which does not require jump
     labels, intended for slow-path usage

   - virtio/vsock: introduce SOCK_SEQPACKET support

   - add getsocketopt to retrieve netns cookie

   - ip: treat lowest address of a IPv4 subnet as ordinary unicast
     address allowing reclaiming of precious IPv4 addresses

   - ipv6: use prandom_u32() for ID generation

   - ip: add support for more flexible field selection for hashing
     across multi-path routes (w/ offload to mlxsw)

   - icmp: add support for extended RFC 8335 PROBE (ping)

   - seg6: add support for SRv6 End.DT46 behavior

   - mptcp:
      - DSS checksum support (RFC 8684) to detect middlebox meddling
      - support Connection-time 'C' flag
      - time stamping support

   - sctp: packetization Layer Path MTU Discovery (RFC 8899)

   - xfrm: speed up state addition with seq set

   - WiFi:
      - hidden AP discovery on 6 GHz and other HE 6 GHz improvements
      - aggregation handling improvements for some drivers
      - minstrel improvements for no-ack frames
      - deferred rate control for TXQs to improve reaction times
      - switch from round robin to virtual time-based airtime scheduler

   - add trace points:
      - tcp checksum errors
      - openvswitch - action execution, upcalls
      - socket errors via sk_error_report

  Device APIs:

   - devlink: add rate API for hierarchical control of max egress rate
     of virtual devices (VFs, SFs etc.)

   - don't require RCU read lock to be held around BPF hooks in NAPI
     context

   - page_pool: generic buffer recycling

  New hardware/drivers:

   - mobile:
      - iosm: PCIe Driver for Intel M.2 Modem
      - support for Qualcomm MSM8998 (ipa)

   - WiFi: Qualcomm QCN9074 and WCN6855 PCI devices

   - sparx5: Microchip SparX-5 family of Enterprise Ethernet switches

   - Mellanox BlueField Gigabit Ethernet (control NIC of the DPU)

   - NXP SJA1110 Automotive Ethernet 10-port switch

   - Qualcomm QCA8327 switch support (qca8k)

   - Mikrotik 10/25G NIC (atl1c)

  Driver changes:

   - ACPI support for some MDIO, MAC and PHY devices from Marvell and
     NXP (our first foray into MAC/PHY description via ACPI)

   - HW timestamping (PTP) support: bnxt_en, ice, sja1105, hns3, tja11xx

   - Mellanox/Nvidia NIC (mlx5)
      - NIC VF offload of L2 bridging
      - support IRQ distribution to Sub-functions

   - Marvell (prestera):
      - add flower and match all
      - devlink trap
      - link aggregation

   - Netronome (nfp): connection tracking offload

   - Intel 1GE (igc): add AF_XDP support

   - Marvell DPU (octeontx2): ingress ratelimit offload

   - Google vNIC (gve): new ring/descriptor format support

   - Qualcomm mobile (rmnet &amp; ipa): inline checksum offload support

   - MediaTek WiFi (mt76)
      - mt7915 MSI support
      - mt7915 Tx status reporting
      - mt7915 thermal sensors support
      - mt7921 decapsulation offload
      - mt7921 enable runtime pm and deep sleep

   - Realtek WiFi (rtw88)
      - beacon filter support
      - Tx antenna path diversity support
      - firmware crash information via devcoredump

   - Qualcomm WiFi (wcn36xx)
      - Wake-on-WLAN support with magic packets and GTK rekeying

   - Micrel PHY (ksz886x/ksz8081): add cable test support"

* tag 'net-next-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (2168 commits)
  tcp: change ICSK_CA_PRIV_SIZE definition
  tcp_yeah: check struct yeah size at compile time
  gve: DQO: Fix off by one in gve_rx_dqo()
  stmmac: intel: set PCI_D3hot in suspend
  stmmac: intel: Enable PHY WOL option in EHL
  net: stmmac: option to enable PHY WOL with PMT enabled
  net: say "local" instead of "static" addresses in ndo_dflt_fdb_{add,del}
  net: use netdev_info in ndo_dflt_fdb_{add,del}
  ptp: Set lookup cookie when creating a PTP PPS source.
  net: sock: add trace for socket errors
  net: sock: introduce sk_error_report
  net: dsa: replay the local bridge FDB entries pointing to the bridge dev too
  net: dsa: ensure during dsa_fdb_offload_notify that dev_hold and dev_put are on the same dev
  net: dsa: include fdb entries pointing to bridge in the host fdb list
  net: dsa: include bridge addresses which are local in the host fdb list
  net: dsa: sync static FDB entries on foreign interfaces to hardware
  net: dsa: install the host MDB and FDB entries in the master's RX filter
  net: dsa: reference count the FDB addresses at the cross-chip notifier level
  net: dsa: introduce a separate cross-chip notifier type for host FDBs
  net: dsa: reference count the MDB entries at the cross-chip notifier level
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull networking updates from Jakub Kicinski:
 "Core:

   - BPF:
      - add syscall program type and libbpf support for generating
        instructions and bindings for in-kernel BPF loaders (BPF loaders
        for BPF), this is a stepping stone for signed BPF programs
      - infrastructure to migrate TCP child sockets from one listener to
        another in the same reuseport group/map to improve flexibility
        of service hand-off/restart
      - add broadcast support to XDP redirect

   - allow bypass of the lockless qdisc to improving performance (for
     pktgen: +23% with one thread, +44% with 2 threads)

   - add a simpler version of "DO_ONCE()" which does not require jump
     labels, intended for slow-path usage

   - virtio/vsock: introduce SOCK_SEQPACKET support

   - add getsocketopt to retrieve netns cookie

   - ip: treat lowest address of a IPv4 subnet as ordinary unicast
     address allowing reclaiming of precious IPv4 addresses

   - ipv6: use prandom_u32() for ID generation

   - ip: add support for more flexible field selection for hashing
     across multi-path routes (w/ offload to mlxsw)

   - icmp: add support for extended RFC 8335 PROBE (ping)

   - seg6: add support for SRv6 End.DT46 behavior

   - mptcp:
      - DSS checksum support (RFC 8684) to detect middlebox meddling
      - support Connection-time 'C' flag
      - time stamping support

   - sctp: packetization Layer Path MTU Discovery (RFC 8899)

   - xfrm: speed up state addition with seq set

   - WiFi:
      - hidden AP discovery on 6 GHz and other HE 6 GHz improvements
      - aggregation handling improvements for some drivers
      - minstrel improvements for no-ack frames
      - deferred rate control for TXQs to improve reaction times
      - switch from round robin to virtual time-based airtime scheduler

   - add trace points:
      - tcp checksum errors
      - openvswitch - action execution, upcalls
      - socket errors via sk_error_report

  Device APIs:

   - devlink: add rate API for hierarchical control of max egress rate
     of virtual devices (VFs, SFs etc.)

   - don't require RCU read lock to be held around BPF hooks in NAPI
     context

   - page_pool: generic buffer recycling

  New hardware/drivers:

   - mobile:
      - iosm: PCIe Driver for Intel M.2 Modem
      - support for Qualcomm MSM8998 (ipa)

   - WiFi: Qualcomm QCN9074 and WCN6855 PCI devices

   - sparx5: Microchip SparX-5 family of Enterprise Ethernet switches

   - Mellanox BlueField Gigabit Ethernet (control NIC of the DPU)

   - NXP SJA1110 Automotive Ethernet 10-port switch

   - Qualcomm QCA8327 switch support (qca8k)

   - Mikrotik 10/25G NIC (atl1c)

  Driver changes:

   - ACPI support for some MDIO, MAC and PHY devices from Marvell and
     NXP (our first foray into MAC/PHY description via ACPI)

   - HW timestamping (PTP) support: bnxt_en, ice, sja1105, hns3, tja11xx

   - Mellanox/Nvidia NIC (mlx5)
      - NIC VF offload of L2 bridging
      - support IRQ distribution to Sub-functions

   - Marvell (prestera):
      - add flower and match all
      - devlink trap
      - link aggregation

   - Netronome (nfp): connection tracking offload

   - Intel 1GE (igc): add AF_XDP support

   - Marvell DPU (octeontx2): ingress ratelimit offload

   - Google vNIC (gve): new ring/descriptor format support

   - Qualcomm mobile (rmnet &amp; ipa): inline checksum offload support

   - MediaTek WiFi (mt76)
      - mt7915 MSI support
      - mt7915 Tx status reporting
      - mt7915 thermal sensors support
      - mt7921 decapsulation offload
      - mt7921 enable runtime pm and deep sleep

   - Realtek WiFi (rtw88)
      - beacon filter support
      - Tx antenna path diversity support
      - firmware crash information via devcoredump

   - Qualcomm WiFi (wcn36xx)
      - Wake-on-WLAN support with magic packets and GTK rekeying

   - Micrel PHY (ksz886x/ksz8081): add cable test support"

* tag 'net-next-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (2168 commits)
  tcp: change ICSK_CA_PRIV_SIZE definition
  tcp_yeah: check struct yeah size at compile time
  gve: DQO: Fix off by one in gve_rx_dqo()
  stmmac: intel: set PCI_D3hot in suspend
  stmmac: intel: Enable PHY WOL option in EHL
  net: stmmac: option to enable PHY WOL with PMT enabled
  net: say "local" instead of "static" addresses in ndo_dflt_fdb_{add,del}
  net: use netdev_info in ndo_dflt_fdb_{add,del}
  ptp: Set lookup cookie when creating a PTP PPS source.
  net: sock: add trace for socket errors
  net: sock: introduce sk_error_report
  net: dsa: replay the local bridge FDB entries pointing to the bridge dev too
  net: dsa: ensure during dsa_fdb_offload_notify that dev_hold and dev_put are on the same dev
  net: dsa: include fdb entries pointing to bridge in the host fdb list
  net: dsa: include bridge addresses which are local in the host fdb list
  net: dsa: sync static FDB entries on foreign interfaces to hardware
  net: dsa: install the host MDB and FDB entries in the master's RX filter
  net: dsa: reference count the FDB addresses at the cross-chip notifier level
  net: dsa: introduce a separate cross-chip notifier type for host FDBs
  net: dsa: reference count the MDB entries at the cross-chip notifier level
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net</title>
<updated>2021-06-29T22:45:27+00:00</updated>
<author>
<name>Jakub Kicinski</name>
<email>kuba@kernel.org</email>
</author>
<published>2021-06-29T22:45:27+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=b6df00789e2831fff7a2c65aa7164b2a4dcbe599'/>
<id>b6df00789e2831fff7a2c65aa7164b2a4dcbe599</id>
<content type='text'>
Trivial conflict in net/netfilter/nf_tables_api.c.

Duplicate fix in tools/testing/selftests/net/devlink_port_split.py
- take the net-next version.

skmsg, and L4 bpf - keep the bpf code but remove the flags
and err params.

Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Trivial conflict in net/netfilter/nf_tables_api.c.

Duplicate fix in tools/testing/selftests/net/devlink_port_split.py
- take the net-next version.

skmsg, and L4 bpf - keep the bpf code but remove the flags
and err params.

Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net: update netdev_rx_csum_fault() print dump only once</title>
<updated>2021-06-28T22:54:57+00:00</updated>
<author>
<name>Tanner Love</name>
<email>tannerlove@google.com</email>
</author>
<published>2021-06-28T13:50:07+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=127d7355abb355b05ff4b42d6e18cc97aa9d1d11'/>
<id>127d7355abb355b05ff4b42d6e18cc97aa9d1d11</id>
<content type='text'>
Printing this stack dump multiple times does not provide additional
useful information, and consumes time in the data path. Printing once
is sufficient.

Changes
  v2: Format indentation properly

Signed-off-by: Tanner Love &lt;tannerlove@google.com&gt;
Acked-by: Eric Dumazet &lt;edumazet@google.com&gt;
Acked-by: Mahesh Bandewar &lt;maheshb@google.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>
Printing this stack dump multiple times does not provide additional
useful information, and consumes time in the data path. Printing once
is sufficient.

Changes
  v2: Format indentation properly

Signed-off-by: Tanner Love &lt;tannerlove@google.com&gt;
Acked-by: Eric Dumazet &lt;edumazet@google.com&gt;
Acked-by: Mahesh Bandewar &lt;maheshb@google.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net: sched: implement TCQ_F_CAN_BYPASS for lockless qdisc</title>
<updated>2021-06-23T19:17:35+00:00</updated>
<author>
<name>Yunsheng Lin</name>
<email>linyunsheng@huawei.com</email>
</author>
<published>2021-06-22T06:49:56+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=c4fef01ba4793a85b2d38a472bddd1e3b56d9585'/>
<id>c4fef01ba4793a85b2d38a472bddd1e3b56d9585</id>
<content type='text'>
Currently pfifo_fast has both TCQ_F_CAN_BYPASS and TCQ_F_NOLOCK
flag set, but queue discipline by-pass does not work for lockless
qdisc because skb is always enqueued to qdisc even when the qdisc
is empty, see __dev_xmit_skb().

This patch calls sch_direct_xmit() to transmit the skb directly
to the driver for empty lockless qdisc, which aviod enqueuing
and dequeuing operation.

As qdisc-&gt;empty is not reliable to indicate a empty qdisc because
there is a time window between enqueuing and setting qdisc-&gt;empty.
So we use the MISSED state added in commit a90c57f2cedd ("net:
sched: fix packet stuck problem for lockless qdisc"), which
indicate there is lock contention, suggesting that it is better
not to do the qdisc bypass in order to avoid packet out of order
problem.

In order to make MISSED state reliable to indicate a empty qdisc,
we need to ensure that testing and clearing of MISSED state is
within the protection of qdisc-&gt;seqlock, only setting MISSED state
can be done without the protection of qdisc-&gt;seqlock. A MISSED
state testing is added without the protection of qdisc-&gt;seqlock to
aviod doing unnecessary spin_trylock() for contention case.

As the enqueuing is not within the protection of qdisc-&gt;seqlock,
there is still a potential data race as mentioned by Jakub [1]:

      thread1               thread2             thread3
qdisc_run_begin() # true
                        qdisc_run_begin(q)
                             set(MISSED)
pfifo_fast_dequeue
  clear(MISSED)
  # recheck the queue
qdisc_run_end()
                            enqueue skb1
                                             qdisc empty # true
                                          qdisc_run_begin() # true
                                          sch_direct_xmit() # skb2
                         qdisc_run_begin()
                            set(MISSED)

When above happens, skb1 enqueued by thread2 is transmited after
skb2 is transmited by thread3 because MISSED state setting and
enqueuing is not under the qdisc-&gt;seqlock. If qdisc bypass is
disabled, skb1 has better chance to be transmited quicker than
skb2.

This patch does not take care of the above data race, because we
view this as similar as below:
Even at the same time CPU1 and CPU2 write the skb to two socket
which both heading to the same qdisc, there is no guarantee that
which skb will hit the qdisc first, because there is a lot of
factor like interrupt/softirq/cache miss/scheduling afffecting
that.

There are below cases that need special handling:
1. When MISSED state is cleared before another round of dequeuing
   in pfifo_fast_dequeue(), and __qdisc_run() might not be able to
   dequeue all skb in one round and call __netif_schedule(), which
   might result in a non-empty qdisc without MISSED set. In order
   to avoid this, the MISSED state is set for lockless qdisc and
   __netif_schedule() will be called at the end of qdisc_run_end.

2. The MISSED state also need to be set for lockless qdisc instead
   of calling __netif_schedule() directly when requeuing a skb for
   a similar reason.

3. For netdev queue stopped case, the MISSED case need clearing
   while the netdev queue is stopped, otherwise there may be
   unnecessary __netif_schedule() calling. So a new DRAINING state
   is added to indicate this case, which also indicate a non-empty
   qdisc.

4. As there is already netif_xmit_frozen_or_stopped() checking in
   dequeue_skb() and sch_direct_xmit(), which are both within the
   protection of qdisc-&gt;seqlock, but the same checking in
   __dev_xmit_skb() is without the protection, which might cause
   empty indication of a lockless qdisc to be not reliable. So
   remove the checking in __dev_xmit_skb(), and the checking in
   the protection of qdisc-&gt;seqlock seems enough to avoid the cpu
   consumption problem for netdev queue stopped case.

1. https://lkml.org/lkml/2021/5/29/215

Acked-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
Tested-by: Vladimir Oltean &lt;vladimir.oltean@nxp.com&gt; # flexcan
Signed-off-by: Yunsheng Lin &lt;linyunsheng@huawei.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>
Currently pfifo_fast has both TCQ_F_CAN_BYPASS and TCQ_F_NOLOCK
flag set, but queue discipline by-pass does not work for lockless
qdisc because skb is always enqueued to qdisc even when the qdisc
is empty, see __dev_xmit_skb().

This patch calls sch_direct_xmit() to transmit the skb directly
to the driver for empty lockless qdisc, which aviod enqueuing
and dequeuing operation.

As qdisc-&gt;empty is not reliable to indicate a empty qdisc because
there is a time window between enqueuing and setting qdisc-&gt;empty.
So we use the MISSED state added in commit a90c57f2cedd ("net:
sched: fix packet stuck problem for lockless qdisc"), which
indicate there is lock contention, suggesting that it is better
not to do the qdisc bypass in order to avoid packet out of order
problem.

In order to make MISSED state reliable to indicate a empty qdisc,
we need to ensure that testing and clearing of MISSED state is
within the protection of qdisc-&gt;seqlock, only setting MISSED state
can be done without the protection of qdisc-&gt;seqlock. A MISSED
state testing is added without the protection of qdisc-&gt;seqlock to
aviod doing unnecessary spin_trylock() for contention case.

As the enqueuing is not within the protection of qdisc-&gt;seqlock,
there is still a potential data race as mentioned by Jakub [1]:

      thread1               thread2             thread3
qdisc_run_begin() # true
                        qdisc_run_begin(q)
                             set(MISSED)
pfifo_fast_dequeue
  clear(MISSED)
  # recheck the queue
qdisc_run_end()
                            enqueue skb1
                                             qdisc empty # true
                                          qdisc_run_begin() # true
                                          sch_direct_xmit() # skb2
                         qdisc_run_begin()
                            set(MISSED)

When above happens, skb1 enqueued by thread2 is transmited after
skb2 is transmited by thread3 because MISSED state setting and
enqueuing is not under the qdisc-&gt;seqlock. If qdisc bypass is
disabled, skb1 has better chance to be transmited quicker than
skb2.

This patch does not take care of the above data race, because we
view this as similar as below:
Even at the same time CPU1 and CPU2 write the skb to two socket
which both heading to the same qdisc, there is no guarantee that
which skb will hit the qdisc first, because there is a lot of
factor like interrupt/softirq/cache miss/scheduling afffecting
that.

There are below cases that need special handling:
1. When MISSED state is cleared before another round of dequeuing
   in pfifo_fast_dequeue(), and __qdisc_run() might not be able to
   dequeue all skb in one round and call __netif_schedule(), which
   might result in a non-empty qdisc without MISSED set. In order
   to avoid this, the MISSED state is set for lockless qdisc and
   __netif_schedule() will be called at the end of qdisc_run_end.

2. The MISSED state also need to be set for lockless qdisc instead
   of calling __netif_schedule() directly when requeuing a skb for
   a similar reason.

3. For netdev queue stopped case, the MISSED case need clearing
   while the netdev queue is stopped, otherwise there may be
   unnecessary __netif_schedule() calling. So a new DRAINING state
   is added to indicate this case, which also indicate a non-empty
   qdisc.

4. As there is already netif_xmit_frozen_or_stopped() checking in
   dequeue_skb() and sch_direct_xmit(), which are both within the
   protection of qdisc-&gt;seqlock, but the same checking in
   __dev_xmit_skb() is without the protection, which might cause
   empty indication of a lockless qdisc to be not reliable. So
   remove the checking in __dev_xmit_skb(), and the checking in
   the protection of qdisc-&gt;seqlock seems enough to avoid the cpu
   consumption problem for netdev queue stopped case.

1. https://lkml.org/lkml/2021/5/29/215

Acked-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
Tested-by: Vladimir Oltean &lt;vladimir.oltean@nxp.com&gt; # flexcan
Signed-off-by: Yunsheng Lin &lt;linyunsheng@huawei.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
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