linux.git/net/core/rtnetlink.c, branch v6.16 Linux kernel source tree net: prevent a NULL deref in rtnl_create_link() 2025-06-05T15:03:00+00:00 Eric Dumazet edumazet@google.com 2025-06-04T10:58:15+00:00 feafc73f3e6ae73371777a037d41d2e31c929636 At the time rtnl_create_link() is running, dev->netdev_ops is NULL, we must not use netdev_lock_ops() or risk a NULL deref if CONFIG_NET_SHAPER is defined. Use netif_set_group() instead of dev_set_group(). RIP: 0010:netdev_need_ops_lock include/net/netdev_lock.h:33 [inline] RIP: 0010:netdev_lock_ops include/net/netdev_lock.h:41 [inline] RIP: 0010:dev_set_group+0xc0/0x230 net/core/dev_api.c:82 Call Trace: <TASK> rtnl_create_link+0x748/0xd10 net/core/rtnetlink.c:3674 rtnl_newlink_create+0x25c/0xb00 net/core/rtnetlink.c:3813 __rtnl_newlink net/core/rtnetlink.c:3940 [inline] rtnl_newlink+0x16d6/0x1c70 net/core/rtnetlink.c:4055 rtnetlink_rcv_msg+0x7cf/0xb70 net/core/rtnetlink.c:6944 netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2534 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline] netlink_unicast+0x75b/0x8d0 net/netlink/af_netlink.c:1339 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1883 sock_sendmsg_nosec net/socket.c:712 [inline] Reported-by: syzbot+9fc858ba0312b42b577e@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/6840265f.a00a0220.d4325.0009.GAE@google.com/T/#u Signed-off-by: Eric Dumazet <edumazet@google.com> Fixes: 7e4d784f5810 ("net: hold netdev instance lock during rtnetlink operations") Acked-by: Stanislav Fomichev <sdf@fomichev.me> Link: https://patch.msgid.link/20250604105815.1516973-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
At the time rtnl_create_link() is running, dev->netdev_ops is NULL,
we must not use netdev_lock_ops() or risk a NULL deref if
CONFIG_NET_SHAPER is defined.

Use netif_set_group() instead of dev_set_group().

 RIP: 0010:netdev_need_ops_lock include/net/netdev_lock.h:33 [inline]
 RIP: 0010:netdev_lock_ops include/net/netdev_lock.h:41 [inline]
 RIP: 0010:dev_set_group+0xc0/0x230 net/core/dev_api.c:82
Call Trace:
 <TASK>
  rtnl_create_link+0x748/0xd10 net/core/rtnetlink.c:3674
  rtnl_newlink_create+0x25c/0xb00 net/core/rtnetlink.c:3813
  __rtnl_newlink net/core/rtnetlink.c:3940 [inline]
  rtnl_newlink+0x16d6/0x1c70 net/core/rtnetlink.c:4055
  rtnetlink_rcv_msg+0x7cf/0xb70 net/core/rtnetlink.c:6944
  netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2534
  netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
  netlink_unicast+0x75b/0x8d0 net/netlink/af_netlink.c:1339
  netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1883
  sock_sendmsg_nosec net/socket.c:712 [inline]

Reported-by: syzbot+9fc858ba0312b42b577e@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/6840265f.a00a0220.d4325.0009.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@google.com>
Fixes: 7e4d784f5810 ("net: hold netdev instance lock during rtnetlink operations")
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250604105815.1516973-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
rtnetlink: do_setlink: Use struct sockaddr_storage 2025-05-27T06:25:43+00:00 Kees Cook kees@kernel.org 2025-05-21T20:46:15+00:00 6b12e0a3c3c9565c7dc106e2a8b1d433b1aa8eb6 Instead of a heap allocating a variably sized struct sockaddr and lying about the type in the call to netif_set_mac_address(), use a stack allocated struct sockaddr_storage. This lets us drop the cast and avoid the allocation. Putting "ss" on the stack means it will get a reused stack slot since it is the same size (128B) as other existing single-scope stack variables, like the vfinfo array (128B), so no additional stack space is used by this function. Acked-by: Gustavo A. R. Silva <gustavoars@kernel.org> Signed-off-by: Kees Cook <kees@kernel.org> Link: https://patch.msgid.link/20250521204619.2301870-7-kees@kernel.org Signed-off-by: Paolo Abeni <pabeni@redhat.com> 
Instead of a heap allocating a variably sized struct sockaddr and lying
about the type in the call to netif_set_mac_address(), use a stack
allocated struct sockaddr_storage. This lets us drop the cast and avoid
the allocation.

Putting "ss" on the stack means it will get a reused stack slot since
it is the same size (128B) as other existing single-scope stack variables,
like the vfinfo array (128B), so no additional stack space is used by
this function.

Acked-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Kees Cook <kees@kernel.org>
Link: https://patch.msgid.link/20250521204619.2301870-7-kees@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
net: core: Switch netif_set_mac_address() to struct sockaddr_storage 2025-05-27T06:25:42+00:00 Kees Cook kees@kernel.org 2025-05-21T20:46:10+00:00 161972650d6795ea00f8b72557cf3c3e593ed250 In order to avoid passing around struct sockaddr that has a size the compiler cannot reason about (nor track at runtime), convert netif_set_mac_address() to take struct sockaddr_storage. This is just a cast conversion, so there is are no binary changes. Following patches will make actual allocation changes. Acked-by: Gustavo A. R. Silva <gustavoars@kernel.org> Signed-off-by: Kees Cook <kees@kernel.org> Link: https://patch.msgid.link/20250521204619.2301870-2-kees@kernel.org Signed-off-by: Paolo Abeni <pabeni@redhat.com> 
In order to avoid passing around struct sockaddr that has a size the
compiler cannot reason about (nor track at runtime), convert
netif_set_mac_address() to take struct sockaddr_storage. This is just a
cast conversion, so there is are no binary changes. Following patches
will make actual allocation changes.

Acked-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Kees Cook <kees@kernel.org>
Link: https://patch.msgid.link/20250521204619.2301870-2-kees@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
net: Use nlmsg_payload in rtnetlink file 2025-04-22T01:38:00+00:00 Breno Leitao leitao@debian.org 2025-04-17T13:03:08+00:00 a45193018001b6fbbaaf4ae2c5c37db426d42d94 Leverage the new nlmsg_payload() helper to avoid checking for message size and then reading the nlmsg data. Signed-off-by: Breno Leitao <leitao@debian.org> Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com> Link: https://patch.msgid.link/20250417-nlmsg_v3-v1-2-9b09d9d7e61d@debian.org Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
Leverage the new nlmsg_payload() helper to avoid checking for message
size and then reading the nlmsg data.

Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250417-nlmsg_v3-v1-2-9b09d9d7e61d@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-04-17T19:26:50+00:00 Jakub Kicinski kuba@kernel.org 2025-04-17T19:23:49+00:00 240ce924d2718b8f6f622f2a9a9c219b9da736e8 Cross-merge networking fixes after downstream PR (net-6.15-rc3). No conflicts. Adjacent changes: tools/net/ynl/pyynl/ynl_gen_c.py 4d07bbf2d456 ("tools: ynl-gen: don't declare loop iterator in place") 7e8ba0c7de2b ("tools: ynl: don't use genlmsghdr in classic netlink") Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
Cross-merge networking fixes after downstream PR (net-6.15-rc3).

No conflicts. Adjacent changes:

tools/net/ynl/pyynl/ynl_gen_c.py
  4d07bbf2d456 ("tools: ynl-gen: don't declare loop iterator in place")
  7e8ba0c7de2b ("tools: ynl: don't use genlmsghdr in classic netlink")

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
net: don't try to ops lock uninitialized devs 2025-04-17T01:28:11+00:00 Jakub Kicinski kuba@kernel.org 2025-04-15T15:15:52+00:00 4798cfa2097f0833d54d8f5ce20ef14631917839 We need to be careful when operating on dev while in rtnl_create_link(). Some devices (vxlan) initialize netdev_ops in ->newlink, so later on. Avoid using netdev_lock_ops(), the device isn't registered so we cannot legally call its ops or generate any notifications for it. netdev_ops_assert_locked_or_invisible() is safe to use, it checks registration status first. Reported-by: syzbot+de1c7d68a10e3f123bdd@syzkaller.appspotmail.com Fixes: 04efcee6ef8d ("net: hold instance lock during NETDEV_CHANGE") Acked-by: Stanislav Fomichev <sdf@fomichev.me> Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com> Link: https://patch.msgid.link/20250415151552.768373-1-kuba@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
We need to be careful when operating on dev while in rtnl_create_link().
Some devices (vxlan) initialize netdev_ops in ->newlink, so later on.
Avoid using netdev_lock_ops(), the device isn't registered so we
cannot legally call its ops or generate any notifications for it.

netdev_ops_assert_locked_or_invisible() is safe to use, it checks
registration status first.

Reported-by: syzbot+de1c7d68a10e3f123bdd@syzkaller.appspotmail.com
Fixes: 04efcee6ef8d ("net: hold instance lock during NETDEV_CHANGE")
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250415151552.768373-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
rtnetlink: Use nlmsg_payload in valid_fdb_dump_strict 2025-04-15T15:28:54+00:00 Breno Leitao leitao@debian.org 2025-04-14T13:24:10+00:00 77d02290366f058dce2555468a48ed8d62d95939 Leverage the new nlmsg_payload() helper to avoid checking for message size and then reading the nlmsg data. Signed-off-by: Breno Leitao <leitao@debian.org> Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com> Link: https://patch.msgid.link/20250414-nlmsg-v2-4-3d90cb42c6af@debian.org Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
Leverage the new nlmsg_payload() helper to avoid checking for message
size and then reading the nlmsg data.

Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250414-nlmsg-v2-4-3d90cb42c6af@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
net: convert dev->rtnl_link_state to a bool 2025-04-14T21:29:54+00:00 Jakub Kicinski kuba@kernel.org 2025-04-10T01:42:46+00:00 097f171f98289cf737437599c40b0d1e81266e9e netdevice reg_state was split into two 16 bit enums back in 2010 in commit a2835763e130 ("rtnetlink: handle rtnl_link netlink notifications manually"). Since the split the fields have been moved apart, and last year we converted reg_state to a normal u8 in commit 4d42b37def70 ("net: convert dev->reg_state to u8"). rtnl_link_state being a 16 bitfield makes no sense. Convert it to a single bool, it seems very unlikely after 15 years that we'll need more values in it. We could drop dev->rtnl_link_ops from the conditions but feels like having it there more clearly points at the reason for this hack. Acked-by: Stanislav Fomichev <sdf@fomichev.me> Link: https://patch.msgid.link/20250410014246.780885-1-kuba@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
netdevice reg_state was split into two 16 bit enums back in 2010
in commit a2835763e130 ("rtnetlink: handle rtnl_link netlink
notifications manually"). Since the split the fields have been
moved apart, and last year we converted reg_state to a normal
u8 in commit 4d42b37def70 ("net: convert dev->reg_state to u8").

rtnl_link_state being a 16 bitfield makes no sense. Convert it
to a single bool, it seems very unlikely after 15 years that
we'll need more values in it.

We could drop dev->rtnl_link_ops from the conditions but feels
like having it there more clearly points at the reason for this
hack.

Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250410014246.780885-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
rtnetlink: Fix bad unlock balance in do_setlink(). 2025-04-08T19:33:22+00:00 Kuniyuki Iwashima kuniyu@amazon.com 2025-04-07T16:42:22+00:00 445e99bdf68d62cc8cd9c129ea177b2b847d654d When validate_linkmsg() fails in do_setlink(), we jump to the errout label and calls netdev_unlock_ops() even though we have not called netdev_lock_ops() as reported by syzbot. [0] Let's return an error directly in such a case. [0] WARNING: bad unlock balance detected! 6.14.0-syzkaller-12504-g8bc251e5d874 #0 Not tainted syz-executor814/5834 is trying to release lock (&dev_instance_lock_key) at: [<ffffffff89f41f56>] netdev_unlock include/linux/netdevice.h:2756 [inline] [<ffffffff89f41f56>] netdev_unlock_ops include/net/netdev_lock.h:48 [inline] [<ffffffff89f41f56>] do_setlink+0xc26/0x43a0 net/core/rtnetlink.c:3406 but there are no more locks to release! other info that might help us debug this: 1 lock held by syz-executor814/5834: #0: ffffffff900fc408 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline] #0: ffffffff900fc408 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline] #0: ffffffff900fc408 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0xd68/0x1fe0 net/core/rtnetlink.c:4064 stack backtrace: CPU: 0 UID: 0 PID: 5834 Comm: syz-executor814 Not tainted 6.14.0-syzkaller-12504-g8bc251e5d874 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120 print_unlock_imbalance_bug+0x185/0x1a0 kernel/locking/lockdep.c:5296 __lock_release kernel/locking/lockdep.c:5535 [inline] lock_release+0x1ed/0x3e0 kernel/locking/lockdep.c:5887 __mutex_unlock_slowpath+0xee/0x800 kernel/locking/mutex.c:907 netdev_unlock include/linux/netdevice.h:2756 [inline] netdev_unlock_ops include/net/netdev_lock.h:48 [inline] do_setlink+0xc26/0x43a0 net/core/rtnetlink.c:3406 rtnl_group_changelink net/core/rtnetlink.c:3783 [inline] __rtnl_newlink net/core/rtnetlink.c:3937 [inline] rtnl_newlink+0x1619/0x1fe0 net/core/rtnetlink.c:4065 rtnetlink_rcv_msg+0x80f/0xd70 net/core/rtnetlink.c:6955 netlink_rcv_skb+0x208/0x480 net/netlink/af_netlink.c:2534 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline] netlink_unicast+0x7f8/0x9a0 net/netlink/af_netlink.c:1339 netlink_sendmsg+0x8c3/0xcd0 net/netlink/af_netlink.c:1883 sock_sendmsg_nosec net/socket.c:712 [inline] __sock_sendmsg+0x221/0x270 net/socket.c:727 ____sys_sendmsg+0x523/0x860 net/socket.c:2566 ___sys_sendmsg net/socket.c:2620 [inline] __sys_sendmsg+0x271/0x360 net/socket.c:2652 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f8427b614a9 Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fff9b59f3a8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007fff9b59f578 RCX: 00007f8427b614a9 RDX: 0000000000000000 RSI: 0000200000000300 RDI: 0000000000000004 RBP: 00007f8427bd4610 R08: 000000000000000c R09: 00007fff9b59f578 R10: 000000000000001b R11: 0000000000000246 R12: 0000000000000001 R13: Fixes: 4c975fd70002 ("net: hold instance lock during NETDEV_REGISTER/UP") Reported-by: syzbot+45016fe295243a7882d3@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=45016fe295243a7882d3 Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Acked-by: Stanislav Fomichev <sdf@fomichev.me> Link: https://patch.msgid.link/20250407164229.24414-1-kuniyu@amazon.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
When validate_linkmsg() fails in do_setlink(), we jump to the errout
label and calls netdev_unlock_ops() even though we have not called
netdev_lock_ops() as reported by syzbot.  [0]

Let's return an error directly in such a case.

[0]
WARNING: bad unlock balance detected!
6.14.0-syzkaller-12504-g8bc251e5d874 #0 Not tainted

syz-executor814/5834 is trying to release lock (&dev_instance_lock_key) at:
[<ffffffff89f41f56>] netdev_unlock include/linux/netdevice.h:2756 [inline]
[<ffffffff89f41f56>] netdev_unlock_ops include/net/netdev_lock.h:48 [inline]
[<ffffffff89f41f56>] do_setlink+0xc26/0x43a0 net/core/rtnetlink.c:3406
but there are no more locks to release!

other info that might help us debug this:
1 lock held by syz-executor814/5834:
 #0: ffffffff900fc408 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
 #0: ffffffff900fc408 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline]
 #0: ffffffff900fc408 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0xd68/0x1fe0 net/core/rtnetlink.c:4064

stack backtrace:
CPU: 0 UID: 0 PID: 5834 Comm: syz-executor814 Not tainted 6.14.0-syzkaller-12504-g8bc251e5d874 #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_unlock_imbalance_bug+0x185/0x1a0 kernel/locking/lockdep.c:5296
 __lock_release kernel/locking/lockdep.c:5535 [inline]
 lock_release+0x1ed/0x3e0 kernel/locking/lockdep.c:5887
 __mutex_unlock_slowpath+0xee/0x800 kernel/locking/mutex.c:907
 netdev_unlock include/linux/netdevice.h:2756 [inline]
 netdev_unlock_ops include/net/netdev_lock.h:48 [inline]
 do_setlink+0xc26/0x43a0 net/core/rtnetlink.c:3406
 rtnl_group_changelink net/core/rtnetlink.c:3783 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3937 [inline]
 rtnl_newlink+0x1619/0x1fe0 net/core/rtnetlink.c:4065
 rtnetlink_rcv_msg+0x80f/0xd70 net/core/rtnetlink.c:6955
 netlink_rcv_skb+0x208/0x480 net/netlink/af_netlink.c:2534
 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
 netlink_unicast+0x7f8/0x9a0 net/netlink/af_netlink.c:1339
 netlink_sendmsg+0x8c3/0xcd0 net/netlink/af_netlink.c:1883
 sock_sendmsg_nosec net/socket.c:712 [inline]
 __sock_sendmsg+0x221/0x270 net/socket.c:727
 ____sys_sendmsg+0x523/0x860 net/socket.c:2566
 ___sys_sendmsg net/socket.c:2620 [inline]
 __sys_sendmsg+0x271/0x360 net/socket.c:2652
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8427b614a9
Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff9b59f3a8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fff9b59f578 RCX: 00007f8427b614a9
RDX: 0000000000000000 RSI: 0000200000000300 RDI: 0000000000000004
RBP: 00007f8427bd4610 R08: 000000000000000c R09: 00007fff9b59f578
R10: 000000000000001b R11: 0000000000000246 R12: 0000000000000001
R13:

Fixes: 4c975fd70002 ("net: hold instance lock during NETDEV_REGISTER/UP")
Reported-by: syzbot+45016fe295243a7882d3@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=45016fe295243a7882d3
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250407164229.24414-1-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
net: hold instance lock during NETDEV_CHANGE 2025-04-07T18:13:39+00:00 Stanislav Fomichev sdf@fomichev.me 2025-04-04T16:11:22+00:00 04efcee6ef8d0f01eef495db047e7216d6e6e38f Cosmin reports an issue with ipv6_add_dev being called from NETDEV_CHANGE notifier: [ 3455.008776] ? ipv6_add_dev+0x370/0x620 [ 3455.010097] ipv6_find_idev+0x96/0xe0 [ 3455.010725] addrconf_add_dev+0x1e/0xa0 [ 3455.011382] addrconf_init_auto_addrs+0xb0/0x720 [ 3455.013537] addrconf_notify+0x35f/0x8d0 [ 3455.014214] notifier_call_chain+0x38/0xf0 [ 3455.014903] netdev_state_change+0x65/0x90 [ 3455.015586] linkwatch_do_dev+0x5a/0x70 [ 3455.016238] rtnl_getlink+0x241/0x3e0 [ 3455.019046] rtnetlink_rcv_msg+0x177/0x5e0 Similarly, linkwatch might get to ipv6_add_dev without ops lock: [ 3456.656261] ? ipv6_add_dev+0x370/0x620 [ 3456.660039] ipv6_find_idev+0x96/0xe0 [ 3456.660445] addrconf_add_dev+0x1e/0xa0 [ 3456.660861] addrconf_init_auto_addrs+0xb0/0x720 [ 3456.661803] addrconf_notify+0x35f/0x8d0 [ 3456.662236] notifier_call_chain+0x38/0xf0 [ 3456.662676] netdev_state_change+0x65/0x90 [ 3456.663112] linkwatch_do_dev+0x5a/0x70 [ 3456.663529] __linkwatch_run_queue+0xeb/0x200 [ 3456.663990] linkwatch_event+0x21/0x30 [ 3456.664399] process_one_work+0x211/0x610 [ 3456.664828] worker_thread+0x1cc/0x380 [ 3456.665691] kthread+0xf4/0x210 Reclassify NETDEV_CHANGE as a notifier that consistently runs under the instance lock. Link: https://lore.kernel.org/netdev/aac073de8beec3e531c86c101b274d434741c28e.camel@nvidia.com/ Reported-by: Cosmin Ratiu <cratiu@nvidia.com> Tested-by: Cosmin Ratiu <cratiu@nvidia.com> Fixes: ad7c7b2172c3 ("net: hold netdev instance lock during sysfs operations") Signed-off-by: Stanislav Fomichev <sdf@fomichev.me> Link: https://patch.msgid.link/20250404161122.3907628-1-sdf@fomichev.me Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
Cosmin reports an issue with ipv6_add_dev being called from
NETDEV_CHANGE notifier:

[ 3455.008776]  ? ipv6_add_dev+0x370/0x620
[ 3455.010097]  ipv6_find_idev+0x96/0xe0
[ 3455.010725]  addrconf_add_dev+0x1e/0xa0
[ 3455.011382]  addrconf_init_auto_addrs+0xb0/0x720
[ 3455.013537]  addrconf_notify+0x35f/0x8d0
[ 3455.014214]  notifier_call_chain+0x38/0xf0
[ 3455.014903]  netdev_state_change+0x65/0x90
[ 3455.015586]  linkwatch_do_dev+0x5a/0x70
[ 3455.016238]  rtnl_getlink+0x241/0x3e0
[ 3455.019046]  rtnetlink_rcv_msg+0x177/0x5e0

Similarly, linkwatch might get to ipv6_add_dev without ops lock:
[ 3456.656261]  ? ipv6_add_dev+0x370/0x620
[ 3456.660039]  ipv6_find_idev+0x96/0xe0
[ 3456.660445]  addrconf_add_dev+0x1e/0xa0
[ 3456.660861]  addrconf_init_auto_addrs+0xb0/0x720
[ 3456.661803]  addrconf_notify+0x35f/0x8d0
[ 3456.662236]  notifier_call_chain+0x38/0xf0
[ 3456.662676]  netdev_state_change+0x65/0x90
[ 3456.663112]  linkwatch_do_dev+0x5a/0x70
[ 3456.663529]  __linkwatch_run_queue+0xeb/0x200
[ 3456.663990]  linkwatch_event+0x21/0x30
[ 3456.664399]  process_one_work+0x211/0x610
[ 3456.664828]  worker_thread+0x1cc/0x380
[ 3456.665691]  kthread+0xf4/0x210

Reclassify NETDEV_CHANGE as a notifier that consistently runs under the
instance lock.

Link: https://lore.kernel.org/netdev/aac073de8beec3e531c86c101b274d434741c28e.camel@nvidia.com/
Reported-by: Cosmin Ratiu <cratiu@nvidia.com>
Tested-by: Cosmin Ratiu <cratiu@nvidia.com>
Fixes: ad7c7b2172c3 ("net: hold netdev instance lock during sysfs operations")
Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250404161122.3907628-1-sdf@fomichev.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>