possible deadlock in obj_cgroup_charge

Status: upstream: reported on 2026/08/01 19:08
Reported-by: syzbot+2034ec28a65521434936@syzkaller.appspotmail.com
First crash: 11d, last: 5d01h
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream possible deadlock in obj_cgroup_charge mm cgroups 4 4 699d 705d 0/29 auto-obsoleted due to no activity on 2024/12/22 06:45

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.1.524/7076 is trying to acquire lock:
ffff8880b8e37de8 (stock_lock){-.-.}-{2:2}, at: local_lock_acquire include/linux/local_lock_internal.h:29 [inline]
ffff8880b8e37de8 (stock_lock){-.-.}-{2:2}, at: consume_obj_stock mm/memcontrol.c:3267 [inline]
ffff8880b8e37de8 (stock_lock){-.-.}-{2:2}, at: obj_cgroup_charge+0xed/0x630 mm/memcontrol.c:3397

but task is already holding lock:
ffff88805fb78a38 (&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
       0xffffffffa00009b2
       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
       mod_objcg_state+0x44b/0x8c0 mm/memcontrol.c:3254
       memcg_slab_post_alloc_hook mm/slab.h:544 [inline]
       slab_post_alloc_hook+0x358/0x4d0 mm/slab.h:778
       slab_alloc_node mm/slub.c:3495 [inline]
       slab_alloc mm/slub.c:3503 [inline]
       __kmem_cache_alloc_lru mm/slub.c:3510 [inline]
       kmem_cache_alloc_lru+0x175/0x2b0 mm/slub.c:3526
       __d_alloc+0x31/0x710 fs/dcache.c:1773
       d_alloc_pseudo+0x1d/0x70 fs/dcache.c:1905
       alloc_file_pseudo+0xe4/0x210 fs/file_table.c:363
       __anon_inode_getfile fs/anon_inodes.c:122 [inline]
       anon_inode_getfile+0xc5/0x1a0 fs/anon_inodes.c:160
       __do_sys_perf_event_open kernel/events/core.c:12889 [inline]
       __se_sys_perf_event_open+0xeed/0x1c60 kernel/events/core.c:12601
       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
       generic_map_update_batch+0x5de/0x800 kernel/bpf/syscall.c:1800
       bpf_map_do_batch+0x3f2/0x600 kernel/bpf/syscall.c:5011
       __sys_bpf+0x381/0x890 kernel/bpf/syscall.c:-1
       __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.1.524/7076:
 #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: ffff88805fb78a38 (&trie->lock){-.-.}-{2:2}, at: trie_update_elem+0xc4/0xd60 kernel/bpf/lpm_trie.c:335

stack backtrace:
CPU: 0 PID: 7076 Comm: syz.1.524 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
 generic_map_update_batch+0x5de/0x800 kernel/bpf/syscall.c:1800
 bpf_map_do_batch+0x3f2/0x600 kernel/bpf/syscall.c:5011
 __sys_bpf+0x381/0x890 kernel/bpf/syscall.c:-1
 __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: 0033:0x7f437779e0d9
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:00007f4378714028 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f4377a25fa0 RCX: 00007f437779e0d9
RDX: 0000000000000038 RSI: 0000200000000640 RDI: 000000000000001a
RBP: 00007f4377835024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4377a26038 R14: 00007f4377a25fa0 R15: 00007ffc8caf3208
 </TASK>

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/08 17:12 linux-6.6.y 6436c12a2ced 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf possible deadlock in obj_cgroup_charge
2026/08/06 23:19 linux-6.6.y 80dfb0405055 c38879ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf possible deadlock in obj_cgroup_charge
2026/08/06 22:47 linux-6.6.y 80dfb0405055 c38879ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf possible deadlock in obj_cgroup_charge
2026/08/06 21:02 linux-6.6.y 80dfb0405055 c38879ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf possible deadlock in obj_cgroup_charge
2026/08/06 20:59 linux-6.6.y 80dfb0405055 c38879ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf possible deadlock in obj_cgroup_charge
2026/08/04 07:55 linux-6.6.y aa0e49877a2e 9451e17e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf possible deadlock in obj_cgroup_charge
2026/08/01 19:07 linux-6.6.y a1153c0deb44 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf possible deadlock in obj_cgroup_charge
* Struck through repros no longer work on HEAD.