linux.git/net/netlink, branch v6.12.80

genetlink: fix genl_bind() invoking bind() after -EPERM

2025-09-19T14:35:48+00:00

[ Upstream commit 1dbfb0363224f6da56f6655d596dc5097308d6f5 ]

Per family bind/unbind callbacks were introduced to allow families
to track multicast group consumer presence, e.g. to start or stop
producing events depending on listeners.

However, in genl_bind() the bind() callback was invoked even if
capability checks failed and ret was set to -EPERM. This means that
callbacks could run on behalf of unauthorized callers while the
syscall still returned failure to user space.

Fix this by only invoking bind() after "if (ret) break;" check
i.e. after permission checks have succeeded.

Fixes: 3de21a8990d3 ("genetlink: Add per family bind/unbind callbacks")
Signed-off-by: Alok Tiwari 
Link: https://patch.msgid.link/20250905135731.3026965-1-alok.a.tiwari@oracle.com
Signed-off-by: Jakub Kicinski 
Signed-off-by: Sasha Levin

net: better track kernel sockets lifetime

2025-08-20T16:30:56+00:00

[ Upstream commit 5c70eb5c593d64d93b178905da215a9fd288a4b5 ]

While kernel sockets are dismantled during pernet_operations->exit(),
their freeing can be delayed by any tx packets still held in qdisc
or device queues, due to skb_set_owner_w() prior calls.

This then trigger the following warning from ref_tracker_dir_exit() [1]

To fix this, make sure that kernel sockets own a reference on net->passive.

Add sk_net_refcnt_upgrade() helper, used whenever a kernel socket
is converted to a refcounted one.

[1]

[  136.263918][   T35] ref_tracker: net notrefcnt@ffff8880638f01e0 has 1/2 users at
[  136.263918][   T35]      sk_alloc+0x2b3/0x370
[  136.263918][   T35]      inet6_create+0x6ce/0x10f0
[  136.263918][   T35]      __sock_create+0x4c0/0xa30
[  136.263918][   T35]      inet_ctl_sock_create+0xc2/0x250
[  136.263918][   T35]      igmp6_net_init+0x39/0x390
[  136.263918][   T35]      ops_init+0x31e/0x590
[  136.263918][   T35]      setup_net+0x287/0x9e0
[  136.263918][   T35]      copy_net_ns+0x33f/0x570
[  136.263918][   T35]      create_new_namespaces+0x425/0x7b0
[  136.263918][   T35]      unshare_nsproxy_namespaces+0x124/0x180
[  136.263918][   T35]      ksys_unshare+0x57d/0xa70
[  136.263918][   T35]      __x64_sys_unshare+0x38/0x40
[  136.263918][   T35]      do_syscall_64+0xf3/0x230
[  136.263918][   T35]      entry_SYSCALL_64_after_hwframe+0x77/0x7f
[  136.263918][   T35]
[  136.343488][   T35] ref_tracker: net notrefcnt@ffff8880638f01e0 has 1/2 users at
[  136.343488][   T35]      sk_alloc+0x2b3/0x370
[  136.343488][   T35]      inet6_create+0x6ce/0x10f0
[  136.343488][   T35]      __sock_create+0x4c0/0xa30
[  136.343488][   T35]      inet_ctl_sock_create+0xc2/0x250
[  136.343488][   T35]      ndisc_net_init+0xa7/0x2b0
[  136.343488][   T35]      ops_init+0x31e/0x590
[  136.343488][   T35]      setup_net+0x287/0x9e0
[  136.343488][   T35]      copy_net_ns+0x33f/0x570
[  136.343488][   T35]      create_new_namespaces+0x425/0x7b0
[  136.343488][   T35]      unshare_nsproxy_namespaces+0x124/0x180
[  136.343488][   T35]      ksys_unshare+0x57d/0xa70
[  136.343488][   T35]      __x64_sys_unshare+0x38/0x40
[  136.343488][   T35]      do_syscall_64+0xf3/0x230
[  136.343488][   T35]      entry_SYSCALL_64_after_hwframe+0x77/0x7f

Fixes: 0cafd77dcd03 ("net: add a refcount tracker for kernel sockets")
Reported-by: syzbot+30a19e01a97420719891@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/67b72aeb.050a0220.14d86d.0283.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet 
Reviewed-by: Kuniyuki Iwashima 
Link: https://patch.msgid.link/20250220131854.4048077-1-edumazet@google.com
Signed-off-by: Jakub Kicinski 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

netlink: avoid infinite retry looping in netlink_unicast()

2025-08-20T16:30:13+00:00

commit 759dfc7d04bab1b0b86113f1164dc1fec192b859 upstream.

netlink_attachskb() checks for the socket's read memory allocation
constraints. Firstly, it has:

  rmem < READ_ONCE(sk->sk_rcvbuf)

to check if the just increased rmem value fits into the socket's receive
buffer. If not, it proceeds and tries to wait for the memory under:

  rmem + skb->truesize > READ_ONCE(sk->sk_rcvbuf)

The checks don't cover the case when skb->truesize + sk->sk_rmem_alloc is
equal to sk->sk_rcvbuf. Thus the function neither successfully accepts
these conditions, nor manages to reschedule the task - and is called in
retry loop for indefinite time which is caught as:

  rcu: INFO: rcu_sched self-detected stall on CPU
  rcu:     0-....: (25999 ticks this GP) idle=ef2/1/0x4000000000000000 softirq=262269/262269 fqs=6212
  (t=26000 jiffies g=230833 q=259957)
  NMI backtrace for cpu 0
  CPU: 0 PID: 22 Comm: kauditd Not tainted 5.10.240 #68
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc42 04/01/2014
  Call Trace:
  
  dump_stack lib/dump_stack.c:120
  nmi_cpu_backtrace.cold lib/nmi_backtrace.c:105
  nmi_trigger_cpumask_backtrace lib/nmi_backtrace.c:62
  rcu_dump_cpu_stacks kernel/rcu/tree_stall.h:335
  rcu_sched_clock_irq.cold kernel/rcu/tree.c:2590
  update_process_times kernel/time/timer.c:1953
  tick_sched_handle kernel/time/tick-sched.c:227
  tick_sched_timer kernel/time/tick-sched.c:1399
  __hrtimer_run_queues kernel/time/hrtimer.c:1652
  hrtimer_interrupt kernel/time/hrtimer.c:1717
  __sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1113
  asm_call_irq_on_stack arch/x86/entry/entry_64.S:808
  

  netlink_attachskb net/netlink/af_netlink.c:1234
  netlink_unicast net/netlink/af_netlink.c:1349
  kauditd_send_queue kernel/audit.c:776
  kauditd_thread kernel/audit.c:897
  kthread kernel/kthread.c:328
  ret_from_fork arch/x86/entry/entry_64.S:304

Restore the original behavior of the check which commit in Fixes
accidentally missed when restructuring the code.

Found by Linux Verification Center (linuxtesting.org).

Fixes: ae8f160e7eb2 ("netlink: Fix wraparounds of sk->sk_rmem_alloc.")
Cc: stable@vger.kernel.org
Signed-off-by: Fedor Pchelkin 
Reviewed-by: Kuniyuki Iwashima 
Link: https://patch.msgid.link/20250728080727.255138-1-pchelkin@ispras.ru
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

netlink: make sure we allow at least one dump skb

2025-07-17T16:37:15+00:00

commit a215b5723922f8099078478122f02100e489cb80 upstream.

Commit under Fixes tightened up the memory accounting for Netlink
sockets. Looks like the accounting is too strict for some existing
use cases, Marek reported issues with nl80211 / WiFi iw CLI.

To reduce number of iterations Netlink dumps try to allocate
messages based on the size of the buffer passed to previous
recvmsg() calls. If user space uses a larger buffer in recvmsg()
than sk_rcvbuf we will allocate an skb we won't be able to queue.

Make sure we always allow at least one skb to be queued.
Same workaround is already present in netlink_attachskb().
Alternative would be to cap the allocation size to
  rcvbuf - rmem_alloc
but as I said, the workaround is already present in other places.

Reported-by: Marek Szyprowski 
Link: https://lore.kernel.org/9794af18-4905-46c6-b12c-365ea2f05858@samsung.com
Fixes: ae8f160e7eb2 ("netlink: Fix wraparounds of sk->sk_rmem_alloc.")
Tested-by: Marek Szyprowski 
Reviewed-by: Kuniyuki Iwashima 
Link: https://patch.msgid.link/20250711001121.3649033-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

netlink: Fix rmem check in netlink_broadcast_deliver().

2025-07-17T16:37:15+00:00

commit a3c4a125ec725cefb40047eb05ff9eafd57830b4 upstream.

We need to allow queuing at least one skb even when skb is
larger than sk->sk_rcvbuf.

The cited commit made a mistake while converting a condition
in netlink_broadcast_deliver().

Let's correct the rmem check for the allow-one-skb rule.

Fixes: ae8f160e7eb24 ("netlink: Fix wraparounds of sk->sk_rmem_alloc.")
Signed-off-by: Kuniyuki Iwashima 
Link: https://patch.msgid.link/20250711053208.2965945-1-kuniyu@google.com
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

netlink: Fix wraparounds of sk->sk_rmem_alloc.

2025-07-17T16:37:05+00:00

[ Upstream commit ae8f160e7eb24240a2a79fc4c815c6a0d4ee16cc ]

Netlink has this pattern in some places

  if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
  	atomic_add(skb->truesize, &sk->sk_rmem_alloc);

, which has the same problem fixed by commit 5a465a0da13e ("udp:
Fix multiple wraparounds of sk->sk_rmem_alloc.").

For example, if we set INT_MAX to SO_RCVBUFFORCE, the condition
is always false as the two operands are of int.

Then, a single socket can eat as many skb as possible until OOM
happens, and we can see multiple wraparounds of sk->sk_rmem_alloc.

Let's fix it by using atomic_add_return() and comparing the two
variables as unsigned int.

Before:
  [root@fedora ~]# ss -f netlink
  Recv-Q      Send-Q Local Address:Port                Peer Address:Port
  -1668710080 0               rtnl:nl_wraparound/293               *

After:
  [root@fedora ~]# ss -f netlink
  Recv-Q     Send-Q Local Address:Port                Peer Address:Port
  2147483072 0               rtnl:nl_wraparound/290               *
  ^
  `--- INT_MAX - 576

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Jason Baron 
Closes: https://lore.kernel.org/netdev/cover.1750285100.git.jbaron@akamai.com/
Signed-off-by: Kuniyuki Iwashima 
Link: https://patch.msgid.link/20250704054824.1580222-1-kuniyu@google.com
Signed-off-by: Jakub Kicinski 
Signed-off-by: Sasha Levin

netlink: fix false positive warning in extack during dumps

2024-12-05T13:02:31+00:00

[ Upstream commit 3bf39fa849ab8ed52abb6715922e6102d3df9f97 ]

Commit under fixes extended extack reporting to dumps.
It works under normal conditions, because extack errors are
usually reported during ->start() or the first ->dump(),
it's quite rare that the dump starts okay but fails later.
If the dump does fail later, however, the input skb will
already have the initiating message pulled, so checking
if bad attr falls within skb->data will fail.

Switch the check to using nlh, which is always valid.

syzbot found a way to hit that scenario by filling up
the receive queue. In this case we initiate a dump
but don't call ->dump() until there is read space for
an skb.

WARNING: CPU: 1 PID: 5845 at net/netlink/af_netlink.c:2210 netlink_ack_tlv_fill+0x1a8/0x560 net/netlink/af_netlink.c:2209
RIP: 0010:netlink_ack_tlv_fill+0x1a8/0x560 net/netlink/af_netlink.c:2209
Call Trace:
 
 netlink_dump_done+0x513/0x970 net/netlink/af_netlink.c:2250
 netlink_dump+0x91f/0xe10 net/netlink/af_netlink.c:2351
 netlink_recvmsg+0x6bb/0x11d0 net/netlink/af_netlink.c:1983
 sock_recvmsg_nosec net/socket.c:1051 [inline]
 sock_recvmsg+0x22f/0x280 net/socket.c:1073
 __sys_recvfrom+0x246/0x3d0 net/socket.c:2267
 __do_sys_recvfrom net/socket.c:2285 [inline]
 __se_sys_recvfrom net/socket.c:2281 [inline]
 __x64_sys_recvfrom+0xde/0x100 net/socket.c:2281
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
 RIP: 0033:0x7ff37dd17a79

Reported-by: syzbot+d4373fa8042c06cefa84@syzkaller.appspotmail.com
Fixes: 8af4f60472fc ("netlink: support all extack types in dumps")
Reviewed-by: Jacob Keller 
Link: https://patch.msgid.link/20241119224432.1713040-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski 
Signed-off-by: Sasha Levin

netlink: terminate outstanding dump on socket close

2024-11-07T21:45:34+00:00

Netlink supports iterative dumping of data. It provides the families
the following ops:
 - start - (optional) kicks off the dumping process
 - dump  - actual dump helper, keeps getting called until it returns 0
 - done  - (optional) pairs with .start, can be used for cleanup
The whole process is asynchronous and the repeated calls to .dump
don't actually happen in a tight loop, but rather are triggered
in response to recvmsg() on the socket.

This gives the user full control over the dump, but also means that
the user can close the socket without getting to the end of the dump.
To make sure .start is always paired with .done we check if there
is an ongoing dump before freeing the socket, and if so call .done.

The complication is that sockets can get freed from BH and .done
is allowed to sleep. So we use a workqueue to defer the call, when
needed.

Unfortunately this does not work correctly. What we defer is not
the cleanup but rather releasing a reference on the socket.
We have no guarantee that we own the last reference, if someone
else holds the socket they may release it in BH and we're back
to square one.

The whole dance, however, appears to be unnecessary. Only the user
can interact with dumps, so we can clean up when socket is closed.
And close always happens in process context. Some async code may
still access the socket after close, queue notification skbs to it etc.
but no dumps can start, end or otherwise make progress.

Delete the workqueue and flush the dump state directly from the release
handler. Note that further cleanup is possible in -next, for instance
we now always call .done before releasing the main module reference,
so dump doesn't have to take a reference of its own.

Reported-by: syzkaller 
Fixes: ed5d7788a934 ("netlink: Do not schedule work from sk_destruct")
Reviewed-by: Kuniyuki Iwashima 
Reviewed-by: Eric Dumazet 
Link: https://patch.msgid.link/20241106015235.2458807-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski

genetlink: hold RCU in genlmsg_mcast()

2024-10-16T00:52:58+00:00

While running net selftests with CONFIG_PROVE_RCU_LIST=y I saw
one lockdep splat [1].

genlmsg_mcast() uses for_each_net_rcu(), and must therefore hold RCU.

Instead of letting all callers guard genlmsg_multicast_allns()
with a rcu_read_lock()/rcu_read_unlock() pair, do it in genlmsg_mcast().

This also means the @flags parameter is useless, we need to always use
GFP_ATOMIC.

[1]
[10882.424136] =============================
[10882.424166] WARNING: suspicious RCU usage
[10882.424309] 6.12.0-rc2-virtme #1156 Not tainted
[10882.424400] -----------------------------
[10882.424423] net/netlink/genetlink.c:1940 RCU-list traversed in non-reader section!!
[10882.424469]
other info that might help us debug this:

[10882.424500]
rcu_scheduler_active = 2, debug_locks = 1
[10882.424744] 2 locks held by ip/15677:
[10882.424791] #0: ffffffffb6b491b0 (cb_lock){++++}-{3:3}, at: genl_rcv (net/netlink/genetlink.c:1219)
[10882.426334] #1: ffffffffb6b49248 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg (net/netlink/genetlink.c:61 net/netlink/genetlink.c:57 net/netlink/genetlink.c:1209)
[10882.426465]
stack backtrace:
[10882.426805] CPU: 14 UID: 0 PID: 15677 Comm: ip Not tainted 6.12.0-rc2-virtme #1156
[10882.426919] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[10882.427046] Call Trace:
[10882.427131]  
[10882.427244] dump_stack_lvl (lib/dump_stack.c:123)
[10882.427335] lockdep_rcu_suspicious (kernel/locking/lockdep.c:6822)
[10882.427387] genlmsg_multicast_allns (net/netlink/genetlink.c:1940 (discriminator 7) net/netlink/genetlink.c:1977 (discriminator 7))
[10882.427436] l2tp_tunnel_notify.constprop.0 (net/l2tp/l2tp_netlink.c:119) l2tp_netlink
[10882.427683] l2tp_nl_cmd_tunnel_create (net/l2tp/l2tp_netlink.c:253) l2tp_netlink
[10882.427748] genl_family_rcv_msg_doit (net/netlink/genetlink.c:1115)
[10882.427834] genl_rcv_msg (net/netlink/genetlink.c:1195 net/netlink/genetlink.c:1210)
[10882.427877] ? __pfx_l2tp_nl_cmd_tunnel_create (net/l2tp/l2tp_netlink.c:186) l2tp_netlink
[10882.427927] ? __pfx_genl_rcv_msg (net/netlink/genetlink.c:1201)
[10882.427959] netlink_rcv_skb (net/netlink/af_netlink.c:2551)
[10882.428069] genl_rcv (net/netlink/genetlink.c:1220)
[10882.428095] netlink_unicast (net/netlink/af_netlink.c:1332 net/netlink/af_netlink.c:1357)
[10882.428140] netlink_sendmsg (net/netlink/af_netlink.c:1901)
[10882.428210] ____sys_sendmsg (net/socket.c:729 (discriminator 1) net/socket.c:744 (discriminator 1) net/socket.c:2607 (discriminator 1))

Fixes: 33f72e6f0c67 ("l2tp : multicast notification to the registered listeners")
Signed-off-by: Eric Dumazet 
Cc: James Chapman 
Cc: Tom Parkin 
Cc: Johannes Berg 
Link: https://patch.msgid.link/20241011171217.3166614-1-edumazet@google.com
Signed-off-by: Jakub Kicinski

net: Fix an unsafe loop on the list

2024-10-04T22:37:15+00:00

The kernel may crash when deleting a genetlink family if there are still
listeners for that family:

Oops: Kernel access of bad area, sig: 11 [#1]
  ...
  NIP [c000000000c080bc] netlink_update_socket_mc+0x3c/0xc0
  LR [c000000000c0f764] __netlink_clear_multicast_users+0x74/0xc0
  Call Trace:
__netlink_clear_multicast_users+0x74/0xc0
genl_unregister_family+0xd4/0x2d0

Change the unsafe loop on the list to a safe one, because inside the
loop there is an element removal from this list.

Fixes: b8273570f802 ("genetlink: fix netns vs. netlink table locking (2)")
Cc: stable@vger.kernel.org
Signed-off-by: Anastasia Kovaleva 
Reviewed-by: Dmitry Bogdanov 
Reviewed-by: Kuniyuki Iwashima 
Link: https://patch.msgid.link/20241003104431.12391-1-a.kovaleva@yadro.com
Signed-off-by: Jakub Kicinski