linux-toradex.git/include/linux/rtnetlink.h, branch v6.17-rc6 Linux kernel for Apalis and Colibri modules 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>
net-sysfs: remove rtnl_trylock from device attributes 2025-02-06T01:49:07+00:00 Antoine Tenart atenart@kernel.org 2025-02-04T17:03:10+00:00 79c61899b5eee317907efd1b0d06a1ada0cc00d8 There is an ABBA deadlock between net device unregistration and sysfs files being accessed[1][2]. To prevent this from happening all paths taking the rtnl lock after the sysfs one (actually kn->active refcount) use rtnl_trylock and return early (using restart_syscall)[3], which can make syscalls to spin for a long time when there is contention on the rtnl lock[4]. There are not many possibilities to improve the above: - Rework the entire net/ locking logic. - Invert two locks in one of the paths — not possible. But here it's actually possible to drop one of the locks safely: the kernfs_node refcount. More details in the code itself, which comes with lots of comments. Note that we check the device is alive in the added sysfs_rtnl_lock helper to disallow sysfs operations to run after device dismantle has started. This also help keeping the same behavior as before. Because of this calls to dev_isalive in sysfs ops were removed. [1] https://lore.kernel.org/netdev/49A4D5D5.5090602@trash.net/ [2] https://lore.kernel.org/netdev/m14oyhis31.fsf@fess.ebiederm.org/ [3] https://lore.kernel.org/netdev/20090226084924.16cb3e08@nehalam/ [4] https://lore.kernel.org/all/20210928125500.167943-1-atenart@kernel.org/T/ Signed-off-by: Antoine Tenart <atenart@kernel.org> Link: https://patch.msgid.link/20250204170314.146022-2-atenart@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
There is an ABBA deadlock between net device unregistration and sysfs
files being accessed[1][2]. To prevent this from happening all paths
taking the rtnl lock after the sysfs one (actually kn->active refcount)
use rtnl_trylock and return early (using restart_syscall)[3], which can
make syscalls to spin for a long time when there is contention on the
rtnl lock[4].

There are not many possibilities to improve the above:
- Rework the entire net/ locking logic.
- Invert two locks in one of the paths — not possible.

But here it's actually possible to drop one of the locks safely: the
kernfs_node refcount. More details in the code itself, which comes with
lots of comments.

Note that we check the device is alive in the added sysfs_rtnl_lock
helper to disallow sysfs operations to run after device dismantle has
started. This also help keeping the same behavior as before. Because of
this calls to dev_isalive in sysfs ops were removed.

[1] https://lore.kernel.org/netdev/49A4D5D5.5090602@trash.net/
[2] https://lore.kernel.org/netdev/m14oyhis31.fsf@fess.ebiederm.org/
[3] https://lore.kernel.org/netdev/20090226084924.16cb3e08@nehalam/
[4] https://lore.kernel.org/all/20210928125500.167943-1-atenart@kernel.org/T/

Signed-off-by: Antoine Tenart <atenart@kernel.org>
Link: https://patch.msgid.link/20250204170314.146022-2-atenart@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
rtnetlink: Add rtnl_net_lock_killable(). 2025-01-07T12:45:53+00:00 Kuniyuki Iwashima kuniyu@amazon.com 2025-01-04T08:21:48+00:00 7bd72a4aa226c3ef752bcd6b33c54f6e85efcc60 rtnl_lock_killable() is used only in register_netdev() and will be converted to per-netns RTNL. Let's unexport it and add the corresponding helper. Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Paolo Abeni <pabeni@redhat.com> 
rtnl_lock_killable() is used only in register_netdev()
and will be converted to per-netns RTNL.

Let's unexport it and add the corresponding helper.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
rtnetlink: remove pad field in ndo_fdb_dump_context 2024-12-11T02:32:33+00:00 Eric Dumazet edumazet@google.com 2024-12-09T10:07:47+00:00 53a6d8912372fc23ea82cc7a49eb59047aa0a650 I chose to remove this field in a separate patch to ease potential bisection, in case one ndo_fdb_dump() is still using the old way (cb->args[2] instead of ctx->fdb_idx) Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Ido Schimmel <idosch@nvidia.com> Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com> Link: https://patch.msgid.link/20241209100747.2269613-4-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
I chose to remove this field in a separate patch to ease
potential bisection, in case one ndo_fdb_dump() is still
using the old way (cb->args[2] instead of ctx->fdb_idx)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20241209100747.2269613-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
rtnetlink: switch rtnl_fdb_dump() to for_each_netdev_dump() 2024-12-11T02:32:32+00:00 Eric Dumazet edumazet@google.com 2024-12-09T10:07:46+00:00 53970a05f799087e2dd2005973609188504e7fcc This is the last netdev iterator still using net->dev_index_head[]. Convert to modern for_each_netdev_dump() for better scalability, and use common patterns in our stack. Following patch in this series removes the pad field in struct ndo_fdb_dump_context. Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Ido Schimmel <idosch@nvidia.com> Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com> Link: https://patch.msgid.link/20241209100747.2269613-3-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
This is the last netdev iterator still using net->dev_index_head[].

Convert to modern for_each_netdev_dump() for better scalability,
and use common patterns in our stack.

Following patch in this series removes the pad field
in struct ndo_fdb_dump_context.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20241209100747.2269613-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
rtnetlink: add ndo_fdb_dump_context 2024-12-11T02:32:32+00:00 Eric Dumazet edumazet@google.com 2024-12-09T10:07:45+00:00 be325f08c432ae5ac6d6594d163e1899cdf202df rtnl_fdb_dump() and various ndo_fdb_dump() helpers share a hidden layout of cb->ctx. Before switching rtnl_fdb_dump() to for_each_netdev_dump() in the following patch, make this more explicit. Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Ido Schimmel <idosch@nvidia.com> Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com> Link: https://patch.msgid.link/20241209100747.2269613-2-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
rtnl_fdb_dump() and various ndo_fdb_dump() helpers share
a hidden layout of cb->ctx.

Before switching rtnl_fdb_dump() to for_each_netdev_dump()
in the following patch, make this more explicit.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20241209100747.2269613-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
net: reformat kdoc return statements 2024-12-09T22:44:59+00:00 Jakub Kicinski kuba@kernel.org 2024-12-05T16:59:14+00:00 3f330db30638b6489d548084a7e8843374d41ad0 kernel-doc -Wall warns about missing Return: statement for non-void functions. We have a number of kdocs in our headers which are missing the colon, IOW they use * Return some value or * Returns some value Having the colon makes some sense, it should help kdoc parser avoid false positives. So add them. This is mostly done with a sed script, and removing the unnecessary cases (mostly the comments which aren't kdoc). Acked-by: Johannes Berg <johannes@sipsolutions.net> Acked-by: Richard Cochran <richardcochran@gmail.com> Acked-by: Sergey Ryazanov <ryazanov.s.a@gmail.com> Reviewed-by: Edward Cree <ecree.xilinx@gmail.com> Acked-by: Alexandra Winter <wintera@linux.ibm.com> Acked-by: Pablo Neira Ayuso <pablo@netfilter.org> Link: https://patch.msgid.link/20241205165914.1071102-1-kuba@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
kernel-doc -Wall warns about missing Return: statement for non-void
functions. We have a number of kdocs in our headers which are missing
the colon, IOW they use
 * Return some value
or
 * Returns some value

Having the colon makes some sense, it should help kdoc parser avoid
false positives. So add them. This is mostly done with a sed script,
and removing the unnecessary cases (mostly the comments which aren't
kdoc).

Acked-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Acked-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Reviewed-by: Edward Cree <ecree.xilinx@gmail.com>
Acked-by: Alexandra Winter <wintera@linux.ibm.com>
Acked-by: Pablo Neira Ayuso <pablo@netfilter.org>
Link: https://patch.msgid.link/20241205165914.1071102-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
rtnetlink: Define rtnl_net_trylock(). 2024-10-29T10:54:57+00:00 Kuniyuki Iwashima kuniyu@amazon.com 2024-10-21T18:32:36+00:00 d1c81818aa227b37d65b40f9883109c5256b9bfb We will need the per-netns version of rtnl_trylock(). rtnl_net_trylock() calls __rtnl_net_lock() only when rtnl_trylock() successfully holds RTNL. When RTNL is removed, we will use mutex_trylock() for per-netns RTNL. Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Paolo Abeni <pabeni@redhat.com> 
We will need the per-netns version of rtnl_trylock().

rtnl_net_trylock() calls __rtnl_net_lock() only when rtnl_trylock()
successfully holds RTNL.

When RTNL is removed, we will use mutex_trylock() for per-netns RTNL.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
rtnetlink: Make per-netns RTNL dereference helpers to macro. 2024-10-29T10:54:57+00:00 Kuniyuki Iwashima kuniyu@amazon.com 2024-10-21T18:32:28+00:00 9cb7e40d388d6c0e4677809c6b2950bc67fd8830 When CONFIG_DEBUG_NET_SMALL_RTNL is off, rtnl_net_dereference() is the static inline wrapper of rtnl_dereference() returning a plain (void *) pointer to make sure net is always evaluated as requested in [0]. But, it makes sparse complain [1] when the pointer has __rcu annotation: net/ipv4/devinet.c:674:47: sparse: warning: incorrect type in argument 2 (different address spaces) net/ipv4/devinet.c:674:47: sparse: expected void *p net/ipv4/devinet.c:674:47: sparse: got struct in_ifaddr [noderef] __rcu * Also, if we evaluate net as (void *) in a macro, then the compiler in turn fails to build due to -Werror=unused-value. #define rtnl_net_dereference(net, p) \ ({ \ (void *)net; \ rtnl_dereference(p); \ }) net/ipv4/devinet.c: In function ‘inet_rtm_deladdr’: ./include/linux/rtnetlink.h:154:17: error: statement with no effect [-Werror=unused-value] 154 | (void *)net; \ net/ipv4/devinet.c:674:21: note: in expansion of macro ‘rtnl_net_dereference’ 674 | (ifa = rtnl_net_dereference(net, *ifap)) != NULL; | ^~~~~~~~~~~~~~~~~~~~ Let's go back to the original simplest macro. Note that checkpatch complains about this approach, but it's one-shot and less noisy than the other two. WARNING: Argument 'net' is not used in function-like macro #76: FILE: include/linux/rtnetlink.h:142: +#define rtnl_net_dereference(net, p) \ + rtnl_dereference(p) Fixes: 844e5e7e656d ("rtnetlink: Add assertion helpers for per-netns RTNL.") Link: https://lore.kernel.org/netdev/20241004132145.7fd208e9@kernel.org/ [0] Reported-by: kernel test robot <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202410200325.SaEJmyZS-lkp@intel.com/ [1] Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Reviewed-by: Simon Horman <horms@kernel.org> Signed-off-by: Paolo Abeni <pabeni@redhat.com> 
When CONFIG_DEBUG_NET_SMALL_RTNL is off, rtnl_net_dereference() is the
static inline wrapper of rtnl_dereference() returning a plain (void *)
pointer to make sure net is always evaluated as requested in [0].

But, it makes sparse complain [1] when the pointer has __rcu annotation:

  net/ipv4/devinet.c:674:47: sparse: warning: incorrect type in argument 2 (different address spaces)
  net/ipv4/devinet.c:674:47: sparse:    expected void *p
  net/ipv4/devinet.c:674:47: sparse:    got struct in_ifaddr [noderef] __rcu *

Also, if we evaluate net as (void *) in a macro, then the compiler
in turn fails to build due to -Werror=unused-value.

  #define rtnl_net_dereference(net, p)                  \
        ({                                              \
                (void *)net;                            \
                rtnl_dereference(p);                    \
        })

  net/ipv4/devinet.c: In function ‘inet_rtm_deladdr’:
  ./include/linux/rtnetlink.h:154:17: error: statement with no effect [-Werror=unused-value]
    154 |                 (void *)net;                            \
  net/ipv4/devinet.c:674:21: note: in expansion of macro ‘rtnl_net_dereference’
    674 |              (ifa = rtnl_net_dereference(net, *ifap)) != NULL;
        |                     ^~~~~~~~~~~~~~~~~~~~

Let's go back to the original simplest macro.

Note that checkpatch complains about this approach, but it's one-shot and
less noisy than the other two.

  WARNING: Argument 'net' is not used in function-like macro
  #76: FILE: include/linux/rtnetlink.h:142:
  +#define rtnl_net_dereference(net, p)			\
  +	rtnl_dereference(p)

Fixes: 844e5e7e656d ("rtnetlink: Add assertion helpers for per-netns RTNL.")
Link: https://lore.kernel.org/netdev/20241004132145.7fd208e9@kernel.org/ [0]
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202410200325.SaEJmyZS-lkp@intel.com/ [1]
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
rtnetlink: Add assertion helpers for per-netns RTNL. 2024-10-08T13:16:59+00:00 Kuniyuki Iwashima kuniyu@amazon.com 2024-10-04T22:10:30+00:00 844e5e7e656d3a7a904fd5607f8491d6fd01db8e Once an RTNL scope is converted with rtnl_net_lock(), we will replace RTNL helper functions inside the scope with the following per-netns alternatives: ASSERT_RTNL() -> ASSERT_RTNL_NET(net) rcu_dereference_rtnl(p) -> rcu_dereference_rtnl_net(net, p) Note that the per-netns helpers are equivalent to the conventional helpers unless CONFIG_DEBUG_NET_SMALL_RTNL is enabled. Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Paolo Abeni <pabeni@redhat.com> 
Once an RTNL scope is converted with rtnl_net_lock(), we will replace
RTNL helper functions inside the scope with the following per-netns
alternatives:

  ASSERT_RTNL()           -> ASSERT_RTNL_NET(net)
  rcu_dereference_rtnl(p) -> rcu_dereference_rtnl_net(net, p)

Note that the per-netns helpers are equivalent to the conventional
helpers unless CONFIG_DEBUG_NET_SMALL_RTNL is enabled.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>