lwn.git/net/netlink/genetlink.c, branch docs-next

genetlink: apply reject policy for split ops on the dispatch path

2026-03-13T01:02:13+00:00

Commit 4fa86555d1cd ("genetlink: piggy back on resv_op to default to a reject policy") added genl_policy_reject_all to ensure that ops without an explicit policy reject all attributes rather than silently accepting them. This change was applied to net. When split ops were later introduced in net-next in commit b8fd60c36a44 ("genetlink: allow families to use split ops directly"), genl_op_fill_in_reject_policy_split() was added and called from genl_op_from_split() (used for policy dumping and registration). However, genl_get_cmd_split(), which is called for incoming messages, copies split_ops entries as-is without applying the reject policy. This means that split ops without policy accept all inputs. This looks like an omission / mistake made when splitting the changes between net and net-next. Let's try to re-introduce the checking. Not considering this a fix given the regression potential. If anyone reports issues we should probably fill in fake policies for specific ops rather than reverting this. Link: https://patch.msgid.link/20260311032839.417748-3-kuba@kernel.org Signed-off-by: Jakub Kicinski

genetlink: use maxattr of 0 for the reject policy

2026-03-13T01:02:13+00:00

Commit 4fa86555d1cd ("genetlink: piggy back on resv_op to default to a reject policy") added genl_policy_reject_all to ensure that ops without an explicit policy reject all attributes rather than silently accepting them. The reject policy had maxattr of 1. Passing info->attrs of size 2 may surprise families. Devlink, for instance, assumes that if info->attrs is set it's safe to access DEVLINK_ATTR_BUS_NAME (1) and DEVLINK_ATTR_DEV_NAME (2). Before plugging reject policies into split ops we need to make sure the genetlink code will not populate info->attrs if family had no explicit policy for the op. While even shared code paths within the families can figure out that given op has no policy fairly easily themselves, passing attrs with fixed size of 2 feels fairly useless and error prone. This change has no user-visible impact, reject attrs are not reported to the user space via getpolicy. We do have to remove the safety check in netlink_policy_dump_get_policy_idx() but it seems to have been there to catch likely faulty input, the code can handle maxattr = 0 just fine. Link: https://patch.msgid.link/20260311032839.417748-2-kuba@kernel.org Signed-off-by: Jakub Kicinski

Convert 'alloc_obj' family to use the new default GFP_KERNEL argument

2026-02-22T01:09:51+00:00

This was done entirely with mindless brute force, using git grep -l '\

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook

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

2025-09-09T00:50:36+00:00

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

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2024-10-21T07:14:18+00:00

Cross-merge networking fixes after downstream PR (net-6.12-rc4). Conflicts: 107a034d5c1e ("net/mlx5: qos: Store rate groups in a qos domain") 1da9cfd6c41c ("net/mlx5: Unregister notifier on eswitch init failure") Signed-off-by: Paolo Abeni

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

genetlink: extend info user-storage to match NL cb ctx

2024-10-10T15:30:21+00:00

This allows a more uniform implementation of non-dump and dump operations, and will be used later in the series to avoid some per-operation allocation. Additionally rename the NL_ASSERT_DUMP_CTX_FITS macro, to fit a more extended usage. Suggested-by: Jakub Kicinski Reviewed-by: Jakub Kicinski Reviewed-by: Jiri Pirko Signed-off-by: Paolo Abeni Link: https://patch.msgid.link/1130cc2896626b84587a2a5f96a5c6829638f4da.1728460186.git.pabeni@redhat.com 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

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