[v6.6] possible deadlock in obj_cgroup_charge

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a1153c0deb44 Linux 6.6.147
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=158ee5b9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0bc3d90c30838b5
dashboard link: https://syzkaller.appspot.com/bug?extid=2034ec28a65521434936
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/049e7649803d/disk-a1153c0d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a2de6430de0a/vmlinux-a1153c0d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c4daf52e89f5/bzImage-a1153c0d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2034ec...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.34/5925 is trying to acquire lock:
ffff8880b8f37de8 (stock_lock){..-.}-{2:2}, at: local_lock_acquire include/linux/local_lock_internal.h:29 [inline]
ffff8880b8f37de8 (stock_lock){..-.}-{2:2}, at: consume_obj_stock mm/memcontrol.c:3267 [inline]
ffff8880b8f37de8 (stock_lock){..-.}-{2:2}, at: obj_cgroup_charge+0xed/0x630 mm/memcontrol.c:3397

but task is already holding lock:
ffff888030eab238 (&trie->lock){-.-.}-{2:2}, at: trie_update_elem+0xc4/0xd60 kernel/bpf/lpm_trie.c:335

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&trie->lock){-.-.}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xb4/0x100 kernel/locking/spinlock.c:162
trie_delete_elem+0x94/0x630 kernel/bpf/lpm_trie.c:466
0xffffffffa00009ea
bpf_dispatcher_nop_func include/linux/bpf.h:1224 [inline]
__bpf_prog_run include/linux/filter.h:617 [inline]
bpf_prog_run include/linux/filter.h:624 [inline]
bpf_prog_run_array include/linux/bpf.h:1994 [inline]
trace_call_bpf+0x333/0x6c0 kernel/trace/bpf_trace.c:143
perf_trace_run_bpf_submit+0x7a/0x1c0 kernel/events/core.c:10287
perf_trace_lock_acquire+0x342/0x400 include/trace/events/lock.h:24
trace_lock_acquire include/trace/events/lock.h:24 [inline]
lock_acquire+0x3ef/0x420 kernel/locking/lockdep.c:5725
rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
rcu_read_lock include/linux/rcupdate.h:786 [inline]
mod_objcg_mlstate+0xad/0x320 mm/memcontrol.c:2913
drain_obj_stock+0x154/0x3a0 mm/memcontrol.c:3321
refill_obj_stock+0x1fc/0x6a0 mm/memcontrol.c:3370
memcg_slab_free_hook+0x123/0x200 mm/slab.h:576
slab_free mm/slub.c:3825 [inline]
kmem_cache_free+0xe1/0x290 mm/slub.c:3852
rcu_do_batch kernel/rcu/tree.c:2194 [inline]
rcu_core+0x9c1/0x17f0 kernel/rcu/tree.c:2467
handle_softirqs+0x27d/0x820 kernel/softirq.c:578
__do_softirq kernel/softirq.c:612 [inline]
invoke_softirq kernel/softirq.c:452 [inline]
__irq_exit_rcu+0xd3/0x190 kernel/softirq.c:661
irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
generic_exec_single+0x477/0x4e0 arch/x86/include/asm/irqflags.h:-1
smp_call_function_single+0x36d/0x5a0 kernel/smp.c:647
task_function_call kernel/events/core.c:120 [inline]
event_function_call+0x351/0x650 kernel/events/core.c:305
_perf_event_period kernel/events/core.c:5898 [inline]
_perf_ioctl kernel/events/core.c:5967 [inline]
perf_ioctl+0x201b/0x24b0 kernel/events/core.c:6068
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (stock_lock){..-.}-{2:2}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3869 [inline]
__lock_acquire+0x37ef/0x7d80 kernel/locking/lockdep.c:5137
lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
local_lock_acquire include/linux/local_lock_internal.h:29 [inline]
consume_obj_stock mm/memcontrol.c:3267 [inline]
obj_cgroup_charge+0x10a/0x630 mm/memcontrol.c:3397
memcg_slab_pre_alloc_hook mm/slab.h:508 [inline]
slab_pre_alloc_hook+0x2e2/0x300 mm/slab.h:719
slab_alloc_node mm/slub.c:3477 [inline]
__kmem_cache_alloc_node+0x53/0x250 mm/slub.c:3534
__do_kmalloc_node mm/slab_common.c:1006 [inline]
__kmalloc_node+0xa6/0x240 mm/slab_common.c:1014
kmalloc_node include/linux/slab.h:620 [inline]
bpf_map_kmalloc_node+0xbc/0x1b0 kernel/bpf/syscall.c:424
lpm_trie_node_alloc kernel/bpf/lpm_trie.c:291 [inline]
trie_update_elem+0x172/0xd60 kernel/bpf/lpm_trie.c:338
bpf_map_update_value+0x64b/0x710 kernel/bpf/syscall.c:203
map_update_elem+0x586/0x710 kernel/bpf/syscall.c:1567
__sys_bpf+0x6b5/0x890 kernel/bpf/syscall.c:5466
__do_sys_bpf kernel/bpf/syscall.c:5582 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5580 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5580
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&trie->lock);
lock(stock_lock);
lock(&trie->lock);
lock(stock_lock);

*** DEADLOCK ***

2 locks held by syz.0.34/5925:
#0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
#0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
#0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: bpf_map_update_value+0x408/0x710 kernel/bpf/syscall.c:202
#1: ffff888030eab238 (&trie->lock){-.-.}-{2:2}, at: trie_update_elem+0xc4/0xd60 kernel/bpf/lpm_trie.c:335

stack backtrace:
CPU: 1 PID: 5925 Comm: syz.0.34 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<TASK>
dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
check_noncircular+0x2fc/0x400 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 kernel/locking/lockdep.c:3869 [inline]
__lock_acquire+0x37ef/0x7d80 kernel/locking/lockdep.c:5137
lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
local_lock_acquire include/linux/local_lock_internal.h:29 [inline]
consume_obj_stock mm/memcontrol.c:3267 [inline]
obj_cgroup_charge+0x10a/0x630 mm/memcontrol.c:3397
memcg_slab_pre_alloc_hook mm/slab.h:508 [inline]
slab_pre_alloc_hook+0x2e2/0x300 mm/slab.h:719
slab_alloc_node mm/slub.c:3477 [inline]
__kmem_cache_alloc_node+0x53/0x250 mm/slub.c:3534
__do_kmalloc_node mm/slab_common.c:1006 [inline]
__kmalloc_node+0xa6/0x240 mm/slab_common.c:1014
kmalloc_node include/linux/slab.h:620 [inline]
bpf_map_kmalloc_node+0xbc/0x1b0 kernel/bpf/syscall.c:424
lpm_trie_node_alloc kernel/bpf/lpm_trie.c:291 [inline]
trie_update_elem+0x172/0xd60 kernel/bpf/lpm_trie.c:338
bpf_map_update_value+0x64b/0x710 kernel/bpf/syscall.c:203
map_update_elem+0x586/0x710 kernel/bpf/syscall.c:1567
__sys_bpf+0x6b5/0x890 kernel/bpf/syscall.c:5466
__do_sys_bpf kernel/bpf/syscall.c:5582 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5580 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5580
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f59a5f9e019
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f59a6f5a028 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f59a6225fa0 RCX: 00007f59a5f9e019
RDX: 0000000000000020 RSI: 00002000000004c0 RDI: 0000000000000002
RBP: 00007f59a603500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f59a6226038 R14: 00007f59a6225fa0 R15: 00007fff495b0658
</TASK>


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