linux.git/net/netlink, branch master

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

net: netlink: Remove the dump_cb_mutex field from struct netlink_sock

2024-08-26T09:35:16+00:00

Commit 5fbf57a937f4 ("net: netlink: remove the cb_mutex "injection" from
netlink core") has removed the usage of the 'dump_cb_mutex' field from the
struct netlink_sock.

Remove the field itself now. It saves a few bytes in the structure.

Signed-off-by: Christophe JAILLET 
Reviewed-by: Simon Horman 
Signed-off-by: David S. Miller

net: netlink: remove the cb_mutex "injection" from netlink core

2024-06-10T12:15:40+00:00

Back in 2007, in commit af65bdfce98d ("[NETLINK]: Switch cb_lock spinlock
to mutex and allow to override it") netlink core was extended to allow
subsystems to replace the dump mutex lock with its own lock.

The mechanism was used by rtnetlink to take rtnl_lock but it isn't
sufficiently flexible for other users. Over the 17 years since
it was added no other user appeared. Since rtnetlink needs conditional
locking now, and doesn't use it either, axe this feature complete.

Signed-off-by: Jakub Kicinski 
Reviewed-by: Kuniyuki Iwashima 
Signed-off-by: David S. Miller

rtnetlink: move rtnl_lock handling out of af_netlink

2024-06-10T12:15:40+00:00

Now that we have an intermediate layer of code for handling
rtnl-level netlink dump quirks, we can move the rtnl_lock
taking there.

For dump handlers with RTNL_FLAG_DUMP_SPLIT_NLM_DONE we can
avoid taking rtnl_lock just to generate NLM_DONE, once again.

Signed-off-by: Jakub Kicinski 
Reviewed-by: Kuniyuki Iwashima 
Reviewed-by: Eric Dumazet 
Signed-off-by: David S. Miller

netlink: support all extack types in dumps

2024-04-23T17:09:49+00:00

Note that when this commit message refers to netlink dump
it only means the actual dumping part, the parsing / dump
start is handled by the same code as "doit".

Commit 4a19edb60d02 ("netlink: Pass extack to dump handlers")
added support for returning extack messages from dump handlers,
but left out other extack info, e.g. bad attribute.

This used to be fine because until YNL we had little practical
use for the machine readable attributes, and only messages were
used in practice.

YNL flips the preference 180 degrees, it's now much more useful
to point to a bad attr with NL_SET_BAD_ATTR() than type
an English message saying "attribute XYZ is $reason-why-bad".

Support all of extack. The fact that extack only gets added if
it fits remains unaddressed.

Reviewed-by: David Ahern 
Link: https://lore.kernel.org/r/20240420023543.3300306-4-kuba@kernel.org
Signed-off-by: Jakub Kicinski

netlink: move extack writing helpers

2024-04-23T17:09:49+00:00

Next change will need them in netlink_dump_done(), pure move.

Reviewed-by: David Ahern 
Link: https://lore.kernel.org/r/20240420023543.3300306-3-kuba@kernel.org
Signed-off-by: Jakub Kicinski

netlink: create a new header for internal genetlink symbols

2024-04-02T04:44:34+00:00

There are things in linux/genetlink.h which are only used
under net/netlink/. Move them to a new local header.
A new header with just 2 externs isn't great, but alternative
would be to include af_netlink.h in genetlink.c which feels
even worse.

Link: https://lore.kernel.org/r/20240329175710.291749-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski

net/netlink: Add getsockopt support for NETLINK_LISTEN_ALL_NSID

2024-03-11T22:48:34+00:00

Currently getsockopt does not support NETLINK_LISTEN_ALL_NSID,
and we are unable to get the value of NETLINK_LISTEN_ALL_NSID
socket option through getsockopt.

This patch adds getsockopt support for NETLINK_LISTEN_ALL_NSID.

Signed-off-by: Juntong Deng 
Link: https://lore.kernel.org/r/AM6PR03MB58482322B7B335308DA56FE599272@AM6PR03MB5848.eurprd03.prod.outlook.com
Signed-off-by: Jakub Kicinski

genetlink: fit NLMSG_DONE into same read() as families

2024-03-06T08:07:45+00:00

Make sure ctrl_fill_info() returns sensible error codes and
propagate them out to netlink core. Let netlink core decide
when to return skb->len and when to treat the exit as an
error. Netlink core does better job at it, if we always
return skb->len the core doesn't know when we're done
dumping and NLMSG_DONE ends up in a separate read().

Reviewed-by: Eric Dumazet 
Signed-off-by: Jakub Kicinski 
Reviewed-by: Ido Schimmel 
Signed-off-by: David S. Miller