linux.git/net/core/dev.h, branch v6.18.21

net: add xmit recursion limit to tunnel xmit functions

2026-03-19T15:08:17+00:00

[ Upstream commit 6f1a9140ecda3baba3d945b9a6155af4268aafc4 ]

Tunnel xmit functions (iptunnel_xmit, ip6tunnel_xmit) lack their own
recursion limit. When a bond device in broadcast mode has GRE tap
interfaces as slaves, and those GRE tunnels route back through the
bond, multicast/broadcast traffic triggers infinite recursion between
bond_xmit_broadcast() and ip_tunnel_xmit()/ip6_tnl_xmit(), causing
kernel stack overflow.

The existing XMIT_RECURSION_LIMIT (8) in the no-qdisc path is not
sufficient because tunnel recursion involves route lookups and full IP
output, consuming much more stack per level. Use a lower limit of 4
(IP_TUNNEL_RECURSION_LIMIT) to prevent overflow.

Add recursion detection using dev_xmit_recursion helpers directly in
iptunnel_xmit() and ip6tunnel_xmit() to cover all IPv4/IPv6 tunnel
paths including UDP encapsulated tunnels (VXLAN, Geneve, etc.).

Move dev_xmit_recursion helpers from net/core/dev.h to public header
include/linux/netdevice.h so they can be used by tunnel code.

 BUG: KASAN: stack-out-of-bounds in blake2s.constprop.0+0xe7/0x160
 Write of size 32 at addr ffff88810033fed0 by task kworker/0:1/11
 Workqueue: mld mld_ifc_work
 Call Trace:
  
  __build_flow_key.constprop.0 (net/ipv4/route.c:515)
  ip_rt_update_pmtu (net/ipv4/route.c:1073)
  iptunnel_xmit (net/ipv4/ip_tunnel_core.c:84)
  ip_tunnel_xmit (net/ipv4/ip_tunnel.c:847)
  gre_tap_xmit (net/ipv4/ip_gre.c:779)
  dev_hard_start_xmit (net/core/dev.c:3887)
  sch_direct_xmit (net/sched/sch_generic.c:347)
  __dev_queue_xmit (net/core/dev.c:4802)
  bond_dev_queue_xmit (drivers/net/bonding/bond_main.c:312)
  bond_xmit_broadcast (drivers/net/bonding/bond_main.c:5279)
  bond_start_xmit (drivers/net/bonding/bond_main.c:5530)
  dev_hard_start_xmit (net/core/dev.c:3887)
  __dev_queue_xmit (net/core/dev.c:4841)
  ip_finish_output2 (net/ipv4/ip_output.c:237)
  ip_output (net/ipv4/ip_output.c:438)
  iptunnel_xmit (net/ipv4/ip_tunnel_core.c:86)
  gre_tap_xmit (net/ipv4/ip_gre.c:779)
  dev_hard_start_xmit (net/core/dev.c:3887)
  sch_direct_xmit (net/sched/sch_generic.c:347)
  __dev_queue_xmit (net/core/dev.c:4802)
  bond_dev_queue_xmit (drivers/net/bonding/bond_main.c:312)
  bond_xmit_broadcast (drivers/net/bonding/bond_main.c:5279)
  bond_start_xmit (drivers/net/bonding/bond_main.c:5530)
  dev_hard_start_xmit (net/core/dev.c:3887)
  __dev_queue_xmit (net/core/dev.c:4841)
  ip_finish_output2 (net/ipv4/ip_output.c:237)
  ip_output (net/ipv4/ip_output.c:438)
  iptunnel_xmit (net/ipv4/ip_tunnel_core.c:86)
  ip_tunnel_xmit (net/ipv4/ip_tunnel.c:847)
  gre_tap_xmit (net/ipv4/ip_gre.c:779)
  dev_hard_start_xmit (net/core/dev.c:3887)
  sch_direct_xmit (net/sched/sch_generic.c:347)
  __dev_queue_xmit (net/core/dev.c:4802)
  bond_dev_queue_xmit (drivers/net/bonding/bond_main.c:312)
  bond_xmit_broadcast (drivers/net/bonding/bond_main.c:5279)
  bond_start_xmit (drivers/net/bonding/bond_main.c:5530)
  dev_hard_start_xmit (net/core/dev.c:3887)
  __dev_queue_xmit (net/core/dev.c:4841)
  mld_sendpack
  mld_ifc_work
  process_one_work
  worker_thread
  

Fixes: 745e20f1b626 ("net: add a recursion limit in xmit path")
Reported-by: Xiang Mei 
Signed-off-by: Weiming Shi 
Link: https://patch.msgid.link/20260306160133.3852900-2-bestswngs@gmail.com
Signed-off-by: Paolo Abeni 
Signed-off-by: Sasha Levin

net: export netdev_get_by_index_lock()

2025-12-18T13:02:56+00:00

[ Upstream commit c07a491c1b735e0c27454ea5c27a446d43401b1e ]

Need to call netdev_get_by_index_lock() from io_uring/zcrx.c, but it is
currently private to net. Export the function in linux/netdevice.h.

Signed-off-by: David Wei 
Acked-by: Jakub Kicinski 
Signed-off-by: Jens Axboe 
Stable-dep-of: b6c5f9454ef3 ("io_uring/zcrx: call netdev_queue_get_dma_dev() under instance lock")
Signed-off-by: Sasha Levin

net: add NUMA awareness to skb_attempt_defer_free()

2025-09-30T13:45:53+00:00

Instead of sharing sd->defer_list & sd->defer_count with
many cpus, add one pair for each NUMA node.

Signed-off-by: Eric Dumazet 
Reviewed-by: Jason Xing 
Reviewed-by: Kuniyuki Iwashima 
Link: https://patch.msgid.link/20250928084934.3266948-4-edumazet@google.com
Signed-off-by: Paolo Abeni

net: prevent deadlocks when enabling NAPIs with mixed kthread config

2025-08-12T12:43:05+00:00

The following order of calls currently deadlocks if:
 - device has threaded=1; and
 - NAPI has persistent config with threaded=0.

  netif_napi_add_weight_config()
    dev->threaded == 1
      napi_kthread_create()

  napi_enable()
    napi_restore_config()
      napi_set_threaded(0)
        napi_stop_kthread()
	  while (NAPIF_STATE_SCHED)
	    msleep(20)

We deadlock because disabled NAPI has STATE_SCHED set.
Creating a thread in netif_napi_add() just to destroy it in
napi_disable() is fairly ugly in the first place. Let's read
both the device config and the NAPI config in netif_napi_add().

Fixes: e6d76268813d ("net: Update threaded state in napi config in netif_set_threaded")
Signed-off-by: Jakub Kicinski 
Reviewed-by: Joe Damato 
Link: https://patch.msgid.link/20250809001205.1147153-4-kuba@kernel.org
Signed-off-by: Paolo Abeni

net: define an enum for the napi threaded state

2025-07-25T01:34:55+00:00

Instead of using '0' and '1' for napi threaded state use an enum with
'disabled' and 'enabled' states.

Tested:
 ./tools/testing/selftests/net/nl_netdev.py
 TAP version 13
 1..7
 ok 1 nl_netdev.empty_check
 ok 2 nl_netdev.lo_check
 ok 3 nl_netdev.page_pool_check
 ok 4 nl_netdev.napi_list_check
 ok 5 nl_netdev.dev_set_threaded
 ok 6 nl_netdev.napi_set_threaded
 ok 7 nl_netdev.nsim_rxq_reset_down
 # Totals: pass:7 fail:0 xfail:0 xpass:0 skip:0 error:0

Signed-off-by: Samiullah Khawaja 
Link: https://patch.msgid.link/20250723013031.2911384-4-skhawaja@google.com
Signed-off-by: Jakub Kicinski

net: Use netif_threaded_enable instead of netif_set_threaded in drivers

2025-07-25T01:34:55+00:00

Prepare for adding an enum type for NAPI threaded states by adding
netif_threaded_enable API. De-export the existing netif_set_threaded API
and only use it internally. Update existing drivers to use
netif_threaded_enable instead of the de-exported netif_set_threaded.

Note that dev_set_threaded used by mt76 debugfs file is unchanged.

Signed-off-by: Samiullah Khawaja 
Link: https://patch.msgid.link/20250723013031.2911384-3-skhawaja@google.com
Signed-off-by: Jakub Kicinski

Add support to set NAPI threaded for individual NAPI

2025-07-15T01:02:37+00:00

A net device has a threaded sysctl that can be used to enable threaded
NAPI polling on all of the NAPI contexts under that device. Allow
enabling threaded NAPI polling at individual NAPI level using netlink.

Extend the netlink operation `napi-set` and allow setting the threaded
attribute of a NAPI. This will enable the threaded polling on a NAPI
context.

Add a test in `nl_netdev.py` that verifies various cases of threaded
NAPI being set at NAPI and at device level.

Tested
 ./tools/testing/selftests/net/nl_netdev.py
 TAP version 13
 1..7
 ok 1 nl_netdev.empty_check
 ok 2 nl_netdev.lo_check
 ok 3 nl_netdev.page_pool_check
 ok 4 nl_netdev.napi_list_check
 ok 5 nl_netdev.dev_set_threaded
 ok 6 nl_netdev.napi_set_threaded
 ok 7 nl_netdev.nsim_rxq_reset_down
 # Totals: pass:7 fail:0 xfail:0 xpass:0 skip:0 error:0

Signed-off-by: Samiullah Khawaja 
Reviewed-by: Willem de Bruijn 
Link: https://patch.msgid.link/20250710211203.3979655-1-skhawaja@google.com
Signed-off-by: Jakub Kicinski

netdev: add "ops compat locking" helpers

2025-04-10T00:01:51+00:00

Add helpers to "lock a netdev in a backward-compatible way",
which for ops-locked netdevs will mean take the instance lock.
For drivers which haven't opted into the ops locking we'll take
rtnl_lock.

The scoped foreach is dropping and re-taking the lock for each
device, even if prev and next are both under rtnl_lock.
I hope that's fine since we expect that netdev nl to be mostly
supported by modern drivers, and modern drivers should also
opt into the instance locking.

Note that these helpers are mostly needed for queue related state,
because drivers modify queue config in their ops in a non-atomic
way. Or differently put, queue changes don't have a clear-cut API
like NAPI configuration. Any state that can should just use the
instance lock directly, not the "compat" hacks.

Reviewed-by: Joe Damato 
Acked-by: Stanislav Fomichev 
Link: https://patch.msgid.link/20250408195956.412733-4-kuba@kernel.org
Signed-off-by: Jakub Kicinski

net: avoid potential race between netdev_get_by_index_lock() and netns switch

2025-04-10T00:01:51+00:00

netdev_get_by_index_lock() performs following steps:

  rcu_lock();
  dev = lookup(netns, ifindex);
  dev_get(dev);
  rcu_unlock();
  [... lock & validate the dev ...]
  return dev

Validation right now only checks if the device is registered but since
the lookup is netns-aware we must also protect against the device
switching netns right after we dropped the RCU lock. Otherwise
the caller in netns1 may get a pointer to a device which has just
switched to netns2.

We can't hold the lock for the entire netns change process (because of
the NETDEV_UNREGISTER notifier), and there's no existing marking to
indicate that the netns is unlisted because of netns move, so add one.

AFAIU none of the existing netdev_get_by_index_lock() callers can
suffer from this problem (NAPI code double checks the netns membership
and other callers are either under rtnl_lock or not ns-sensitive),
so this patch does not have to be treated as a fix.

Reviewed-by: Joe Damato 
Acked-by: Stanislav Fomichev 
Link: https://patch.msgid.link/20250408195956.412733-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski

net: rps: remove kfree_rcu_mightsleep() use

2025-04-08T19:30:55+00:00

Add an rcu_head to sd_flow_limit and rps_sock_flow_table structs
to use the more conventional and predictable k[v]free_rcu().

Signed-off-by: Eric Dumazet 
Reviewed-by: Willem de Bruijn 
Link: https://patch.msgid.link/20250407163602.170356-5-edumazet@google.com
Signed-off-by: Jakub Kicinski