[syzbot] [bpf?] possible deadlock in trie_update_elem

From: syzbot
Date: Wed Mar 27 2024 - 19:12:35 EST

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Hello,

syzbot found the following issue on:

HEAD commit: fe46a7dd189e Merge tag 'sound-6.9-rc1' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1404a7b6180000
kernel config: https://syzkaller.appspot.com/x/.config?x=4d90a36f0cab495a
dashboard link: https://syzkaller.appspot.com/bug?extid=ea624e536fee669a05cf
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f6c04726a2ae/disk-fe46a7dd.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/09c26ce901ea/vmlinux-fe46a7dd.xz
kernel image: https://storage.googleapis.com/syzbot-assets/134acf7f5322/bzImage-fe46a7dd.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ea624e536fee669a05cf@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
6.8.0-syzkaller-08951-gfe46a7dd189e #0 Not tainted
------------------------------------------------------
syz-executor.2/14356 is trying to acquire lock:
ffff88813fffece0 (&pgdat->kswapd_wait){....}-{2:2}, at: __wake_up_common_lock+0x25/0x1e0 kernel/sched/wait.c:105

but task is already holding lock:
ffff88807ab571f8 (&trie->lock){....}-{2:2}, at: trie_update_elem+0xcb/0xc10 kernel/bpf/lpm_trie.c:324

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #3 (&trie->lock){....}-{2:2}:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
trie_delete_elem+0x96/0x6a0 kernel/bpf/lpm_trie.c:451
0xffffffffa000080e
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run include/linux/filter.h:664 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
bpf_trace_run4+0x25a/0x490 kernel/trace/bpf_trace.c:2422
trace_sched_switch include/trace/events/sched.h:222 [inline]
__schedule+0x250b/0x49d0 kernel/sched/core.c:6733
preempt_schedule_common+0x84/0xd0 kernel/sched/core.c:6915
preempt_schedule+0xe1/0xf0 kernel/sched/core.c:6939
preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:12
__local_bh_enable_ip+0x179/0x200 kernel/softirq.c:389
spin_unlock_bh include/linux/spinlock.h:396 [inline]
batadv_nc_purge_paths+0x30f/0x3b0 net/batman-adv/network-coding.c:471
batadv_nc_worker+0x328/0x610 net/batman-adv/network-coding.c:720
process_one_work kernel/workqueue.c:3254 [inline]
process_scheduled_works+0xa00/0x1770 kernel/workqueue.c:3335
worker_thread+0x86d/0xd70 kernel/workqueue.c:3416
kthread+0x2f0/0x390 kernel/kthread.c:388
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243

-> #2 (&rq->__lock){-.-.}-{2:2}:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
_raw_spin_lock_nested+0x31/0x40 kernel/locking/spinlock.c:378
raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:559
raw_spin_rq_lock kernel/sched/sched.h:1385 [inline]
rq_lock kernel/sched/sched.h:1699 [inline]
task_fork_fair+0x61/0x1e0 kernel/sched/fair.c:12629
sched_cgroup_fork+0x37c/0x410 kernel/sched/core.c:4845
copy_process+0x2217/0x3df0 kernel/fork.c:2498
kernel_clone+0x223/0x840 kernel/fork.c:2796
user_mode_thread+0x132/0x1a0 kernel/fork.c:2874
rest_init+0x27/0x300 init/main.c:695
arch_call_rest_init+0xe/0x10 init/main.c:831
start_kernel+0x47a/0x500 init/main.c:1077
x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:509
x86_64_start_kernel+0x99/0xa0 arch/x86/kernel/head64.c:490
common_startup_64+0x13e/0x147

-> #1 (&p->pi_lock){-.-.}-{2:2}:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:553 [inline]
try_to_wake_up+0xb0/0x1470 kernel/sched/core.c:4262
autoremove_wake_function+0x16/0x110 kernel/sched/wait.c:384
__wake_up_common kernel/sched/wait.c:89 [inline]
__wake_up_common_lock+0x130/0x1e0 kernel/sched/wait.c:106
rmqueue mm/page_alloc.c:2913 [inline]
get_page_from_freelist+0x30ab/0x3580 mm/page_alloc.c:3308
__alloc_pages+0x256/0x680 mm/page_alloc.c:4569
alloc_pages_mpol+0x3de/0x650 mm/mempolicy.c:2133
shmem_alloc_folio mm/shmem.c:1634 [inline]
shmem_alloc_and_add_folio+0x250/0xdf0 mm/shmem.c:1674
shmem_get_folio_gfp+0x82d/0x1f50 mm/shmem.c:2061
shmem_get_folio mm/shmem.c:2166 [inline]
shmem_write_begin+0x170/0x4d0 mm/shmem.c:2750
generic_perform_write+0x322/0x640 mm/filemap.c:3930
shmem_file_write_iter+0xfc/0x120 mm/shmem.c:2926
call_write_iter include/linux/fs.h:2108 [inline]
new_sync_write fs/read_write.c:497 [inline]
vfs_write+0xa84/0xcb0 fs/read_write.c:590
ksys_write+0x1a0/0x2c0 fs/read_write.c:643
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #0 (&pgdat->kswapd_wait){....}-{2:2}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
__wake_up_common_lock+0x25/0x1e0 kernel/sched/wait.c:105
rmqueue mm/page_alloc.c:2913 [inline]
get_page_from_freelist+0x30ab/0x3580 mm/page_alloc.c:3308
__alloc_pages+0x256/0x680 mm/page_alloc.c:4569
__alloc_pages_node include/linux/gfp.h:238 [inline]
alloc_pages_node include/linux/gfp.h:261 [inline]
__kmalloc_large_node+0x91/0x1f0 mm/slub.c:3911
__do_kmalloc_node mm/slub.c:3954 [inline]
__kmalloc_node+0x33e/0x4e0 mm/slub.c:3973
kmalloc_node include/linux/slab.h:648 [inline]
bpf_map_kmalloc_node+0xd3/0x1c0 kernel/bpf/syscall.c:422
lpm_trie_node_alloc kernel/bpf/lpm_trie.c:291 [inline]
trie_update_elem+0x1d3/0xc10 kernel/bpf/lpm_trie.c:333
bpf_map_update_value+0x4d3/0x540 kernel/bpf/syscall.c:203
map_update_elem+0x53a/0x6f0 kernel/bpf/syscall.c:1641
__sys_bpf+0x76f/0x810 kernel/bpf/syscall.c:5619
__do_sys_bpf kernel/bpf/syscall.c:5738 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5736 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5736
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75

other info that might help us debug this:

Chain exists of:
&pgdat->kswapd_wait --> &rq->__lock --> &trie->lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&trie->lock);
lock(&rq->__lock);
lock(&trie->lock);
lock(&pgdat->kswapd_wait);

*** DEADLOCK ***

2 locks held by syz-executor.2/14356:
#0: ffffffff8e132020 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:298 [inline]
#0: ffffffff8e132020 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:750 [inline]
#0: ffffffff8e132020 (rcu_read_lock){....}-{1:2}, at: bpf_map_update_value+0x3c4/0x540 kernel/bpf/syscall.c:202
#1: ffff88807ab571f8 (&trie->lock){....}-{2:2}, at: trie_update_elem+0xcb/0xc10 kernel/bpf/lpm_trie.c:324

stack backtrace:
CPU: 1 PID: 14356 Comm: syz-executor.2 Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2187
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
__wake_up_common_lock+0x25/0x1e0 kernel/sched/wait.c:105
rmqueue mm/page_alloc.c:2913 [inline]
get_page_from_freelist+0x30ab/0x3580 mm/page_alloc.c:3308
__alloc_pages+0x256/0x680 mm/page_alloc.c:4569
__alloc_pages_node include/linux/gfp.h:238 [inline]
alloc_pages_node include/linux/gfp.h:261 [inline]
__kmalloc_large_node+0x91/0x1f0 mm/slub.c:3911
__do_kmalloc_node mm/slub.c:3954 [inline]
__kmalloc_node+0x33e/0x4e0 mm/slub.c:3973
kmalloc_node include/linux/slab.h:648 [inline]
bpf_map_kmalloc_node+0xd3/0x1c0 kernel/bpf/syscall.c:422
lpm_trie_node_alloc kernel/bpf/lpm_trie.c:291 [inline]
trie_update_elem+0x1d3/0xc10 kernel/bpf/lpm_trie.c:333
bpf_map_update_value+0x4d3/0x540 kernel/bpf/syscall.c:203
map_update_elem+0x53a/0x6f0 kernel/bpf/syscall.c:1641
__sys_bpf+0x76f/0x810 kernel/bpf/syscall.c:5619
__do_sys_bpf kernel/bpf/syscall.c:5738 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5736 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5736
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7f7c6647dda9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f7c6728c0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f7c665abf80 RCX: 00007f7c6647dda9
RDX: 0000000000000020 RSI: 0000000020000140 RDI: 0000000000000002
RBP: 00007f7c664ca47a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f7c665abf80 R15: 00007fff403ef148
</TASK>

---
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