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Eric Dumazet 03ca631c07 genetlink: hold RCU in genlmsg_mcast() 
[ Upstream commit 56440d7ec2 ]

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]  <TASK>
[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: 33f72e6f0c ("l2tp : multicast notification to the registered listeners")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: James Chapman <jchapman@katalix.com>
Cc: Tom Parkin <tparkin@katalix.com>
Cc: Johannes Berg <johannes.berg@intel.com>
Link: https://patch.msgid.link/20241011171217.3166614-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2024-11-01 01:52:34 +01:00
..
acpi ACPI: CPPC: Fix MASK_VAL() usage 2024-10-17 15:10:44 +02:00
asm-generic vmlinux.lds.h: catch .bss..L* sections into BSS") 2024-08-19 05:44:54 +02:00
clocksource drivers: hv: Decouple Hyper-V clock/timer code from VMbus drivers 2021-07-19 09:24:28 +00:00
crypto crypto: af_alg - Disallow multiple in-flight AIO requests 2024-01-25 14:52:34 -08:00
drm drm/printer: Allow NULL data in devcoredump printer 2024-10-17 15:11:32 +02:00
dt-bindings dt-bindings: clock: qcom: Add GPLL9 support on gcc-sc8180x 2024-10-17 15:11:46 +02:00
keys KEYS: trusted: allow use of kernel RNG for key material 2023-10-19 23:05:33 +02:00
kunit kunit: fix kernel-doc warnings due to mismatched arg names 2021-10-06 17:54:07 -06:00
kvm KVM: arm64: vgic-v4: Make the doorbell request robust w.r.t preemption 2024-07-05 09:14:51 +02:00
linux irqchip/gic-v4: Don't allow a VMOVP on a dying VPE 2024-10-22 15:40:46 +02:00
math-emu math-emu: Fix fall-through warning 2021-07-13 13:57:44 -05:00
media media: cec: core: add adap_nb_transmit_canceled() callback 2024-06-16 13:39:53 +02:00
memory memory: renesas-rpc-if: Fix HF/OSPI data transfer in Manual Mode 2022-05-09 09:14:34 +02:00
misc ocxl: Update the Process Element Entry 2020-12-04 01:01:30 +11:00
net genetlink: hold RCU in genlmsg_mcast() 2024-11-01 01:52:34 +01:00
pcmcia pcmcia: Replace zero-length array with flexible-array 2020-05-18 10:28:31 +02:00
ras Revert "mm/memory-failure.c: fix race with changing page compound again" 2022-07-12 16:35:17 +02:00
rdma RDMA/core: Fix umem iterator when PAGE_SIZE is greater then HCA pgsz 2023-12-13 18:36:40 +01:00
scsi scsi: core: Fix the return value of scsi_logical_block_count() 2024-09-04 13:23:35 +02:00
soc soc: qcom: rpmh-rsc: Enhance check for VRM in-flight request 2024-06-16 13:39:55 +02:00
sound ALSA: dmaengine: Synchronize dma channel after drop() 2024-07-27 10:46:11 +02:00
target scsi: target: Fix multiple LUN_RESET handling 2023-05-11 23:00:26 +09:00
trace f2fs: reduce expensive checkpoint trigger frequency 2024-10-17 15:11:04 +02:00
uapi bpf: Make sure internal and UAPI bpf_redirect flags don't overlap 2024-11-01 01:52:31 +01:00
vdso time64.h: Consolidated PSEC_PER_SEC definition 2021-04-06 16:32:17 -07:00
video video: of_display_timing.h: include errno.h 2022-07-12 16:35:10 +02:00
xen ACPI: processor: Fix evaluating _PDC method when running as Xen dom0 2023-05-11 23:00:22 +09:00