nexthop: Fix splat with CONFIG_DEBUG_PREEMPT=y
Locally generated packets can increment the new nexthop statistics from
process context, resulting in the following splat [1] due to preemption
being enabled. Fix by using get_cpu_ptr() / put_cpu_ptr() which will
which take care of disabling / enabling preemption.
BUG: using smp_processor_id() in preemptible [
00000000] code: ping/949
caller is nexthop_select_path+0xcf8/0x1e30
CPU: 12 PID: 949 Comm: ping Not tainted
6.8.0-rc7-custom-gcb450f605fae #11
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-1.fc38 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0xbd/0xe0
check_preemption_disabled+0xce/0xe0
nexthop_select_path+0xcf8/0x1e30
fib_select_multipath+0x865/0x18b0
fib_select_path+0x311/0x1160
ip_route_output_key_hash_rcu+0xe54/0x2720
ip_route_output_key_hash+0x193/0x380
ip_route_output_flow+0x25/0x130
raw_sendmsg+0xbab/0x34a0
inet_sendmsg+0xa2/0xe0
__sys_sendto+0x2ad/0x430
__x64_sys_sendto+0xe5/0x1c0
do_syscall_64+0xc5/0x1d0
entry_SYSCALL_64_after_hwframe+0x63/0x6b
[...]
Fixes: f4676ea74b85 ("net: nexthop: Add nexthop group entry stats")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20240311162307.545385-5-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>