syzbot

BUG: sleeping function called from invalid context at include/linux/sched/mm.h:209
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 3960, name: syz-executor633
2 locks held by syz-executor633/3960:
 #0: ffff8000169d6ea8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:72 [inline]
 #0: ffff8000169d6ea8 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0xa2c/0xdac net/core/rtnetlink.c:5590
 #1: ffff0000c120e108 (&sch->q.lock){+...}-{2:2}, at: netem_change+0x22c/0x1a90 net/sched/sch_netem.c:972
Preemption disabled at:
[<ffff800010049c20>] netem_change+0x22c/0x1a90 net/sched/sch_netem.c:972
CPU: 1 PID: 3960 Comm: syz-executor633 Not tainted 5.15.119-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
Call trace:
 dump_backtrace+0x0/0x530 arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x108/0x170 lib/dump_stack.c:106
 dump_stack+0x1c/0x58 lib/dump_stack.c:113
 ___might_sleep+0x380/0x4dc kernel/sched/core.c:9625
 __might_sleep+0x98/0xf0 kernel/sched/core.c:9579
 might_alloc include/linux/sched/mm.h:209 [inline]
 slab_pre_alloc_hook+0x58/0xe8 mm/slab.h:492
 slab_alloc_node mm/slub.c:3134 [inline]
 __kmalloc_node+0xbc/0x5b8 mm/slub.c:4451
 kmalloc_node include/linux/slab.h:614 [inline]
 kvmalloc_node+0x88/0x204 mm/util.c:619
 kvmalloc include/linux/mm.h:805 [inline]
 get_dist_table+0x9c/0x2a4 net/sched/sch_netem.c:788
 netem_change+0x7cc/0x1a90 net/sched/sch_netem.c:988
 netem_init+0x54/0xb8 net/sched/sch_netem.c:1075
 qdisc_create+0x6fc/0xf44 net/sched/sch_api.c:1264
 tc_modify_qdisc+0x8dc/0x1344
 rtnetlink_rcv_msg+0xa74/0xdac net/core/rtnetlink.c:5593
 netlink_rcv_skb+0x20c/0x3b8 net/netlink/af_netlink.c:2504
 rtnetlink_rcv+0x28/0x38 net/core/rtnetlink.c:5611
 netlink_unicast_kernel net/netlink/af_netlink.c:1330 [inline]
 netlink_unicast+0x664/0x938 net/netlink/af_netlink.c:1356
 netlink_sendmsg+0x844/0xb38 net/netlink/af_netlink.c:1923
 sock_sendmsg_nosec net/socket.c:704 [inline]
 sock_sendmsg net/socket.c:724 [inline]
 ____sys_sendmsg+0x584/0x870 net/socket.c:2412
 ___sys_sendmsg+0x214/0x294 net/socket.c:2466
 __sys_sendmsg net/socket.c:2495 [inline]
 __do_sys_sendmsg net/socket.c:2504 [inline]
 __se_sys_sendmsg net/socket.c:2502 [inline]
 __arm64_sys_sendmsg+0x1ac/0x25c net/socket.c:2502
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
 el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:596
 el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:614
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

============================================
WARNING: possible recursive locking detected
5.15.119-syzkaller #0 Tainted: G        W        
--------------------------------------------
syz-executor633/3960 is trying to acquire lock:
ffff0000c120e108 (&sch->q.lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:368 [inline]
ffff0000c120e108 (&sch->q.lock){+...}-{2:2}, at: get_dist_table+0x1f0/0x2a4 net/sched/sch_netem.c:798

but task is already holding lock:
ffff0000c120e108 (&sch->q.lock){+...}-{2:2}, at: netem_change+0x22c/0x1a90 net/sched/sch_netem.c:972

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&sch->q.lock);
  lock(&sch->q.lock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

2 locks held by syz-executor633/3960:
 #0: ffff8000169d6ea8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:72 [inline]
 #0: ffff8000169d6ea8 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0xa2c/0xdac net/core/rtnetlink.c:5590
 #1: ffff0000c120e108 (&sch->q.lock){+...}-{2:2}, at: netem_change+0x22c/0x1a90 net/sched/sch_netem.c:972

stack backtrace:
CPU: 1 PID: 3960 Comm: syz-executor633 Tainted: G        W         5.15.119-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
Call trace:
 dump_backtrace+0x0/0x530 arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x108/0x170 lib/dump_stack.c:106
 dump_stack+0x1c/0x58 lib/dump_stack.c:113
 __lock_acquire+0x62b4/0x7620 kernel/locking/lockdep.c:5011
 lock_acquire+0x240/0x77c kernel/locking/lockdep.c:5622
 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
 _raw_spin_lock_bh+0x124/0x1c4 kernel/locking/spinlock.c:178
 spin_lock_bh include/linux/spinlock.h:368 [inline]
 get_dist_table+0x1f0/0x2a4 net/sched/sch_netem.c:798
 netem_change+0x7cc/0x1a90 net/sched/sch_netem.c:988
 netem_init+0x54/0xb8 net/sched/sch_netem.c:1075
 qdisc_create+0x6fc/0xf44 net/sched/sch_api.c:1264
 tc_modify_qdisc+0x8dc/0x1344
 rtnetlink_rcv_msg+0xa74/0xdac net/core/rtnetlink.c:5593
 netlink_rcv_skb+0x20c/0x3b8 net/netlink/af_netlink.c:2504
 rtnetlink_rcv+0x28/0x38 net/core/rtnetlink.c:5611
 netlink_unicast_kernel net/netlink/af_netlink.c:1330 [inline]
 netlink_unicast+0x664/0x938 net/netlink/af_netlink.c:1356
 netlink_sendmsg+0x844/0xb38 net/netlink/af_netlink.c:1923
 sock_sendmsg_nosec net/socket.c:704 [inline]
 sock_sendmsg net/socket.c:724 [inline]
 ____sys_sendmsg+0x584/0x870 net/socket.c:2412
 ___sys_sendmsg+0x214/0x294 net/socket.c:2466
 __sys_sendmsg net/socket.c:2495 [inline]
 __do_sys_sendmsg net/socket.c:2504 [inline]
 __se_sys_sendmsg net/socket.c:2502 [inline]
 __arm64_sys_sendmsg+0x1ac/0x25c net/socket.c:2502
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
 el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:596
 el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:614
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584