Hi, On 4/15/2024 10:28 AM, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 7efd0a74039f Merge tag 'ata-6.9-rc4' of git://git.kernel.o.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=1358aeed180000 > kernel config: https://syzkaller.appspot.com/x/.config?x=285be8dd6baeb438 > dashboard link: https://syzkaller.appspot.com/bug?extid=a7f061d2d16154538c58 > compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-7efd0a74.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/39eb4e17e7f0/vmlinux-7efd0a74.xz > kernel image: https://storage.googleapis.com/syzbot-assets/b9a08c36e0ca/bzImage-7efd0a74.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+a7f061d2d16154538c58@xxxxxxxxxxxxxxxxxxxxxxxxx > > ====================================================== > WARNING: possible circular locking dependency detected > 6.9.0-rc3-syzkaller-00355-g7efd0a74039f #0 Not tainted > ------------------------------------------------------ > syz-executor.2/7645 is trying to acquire lock: > ffff88807ffd7d58 (&zone->lock){-.-.}-{2:2}, at: rmqueue_buddy mm/page_alloc.c:2730 [inline] > ffff88807ffd7d58 (&zone->lock){-.-.}-{2:2}, at: rmqueue mm/page_alloc.c:2911 [inline] > ffff88807ffd7d58 (&zone->lock){-.-.}-{2:2}, at: get_page_from_freelist+0x4b9/0x3780 mm/page_alloc.c:3314 > > but task is already holding lock: > ffff88802c8739f8 (&trie->lock){-.-.}-{2:2}, at: trie_update_elem+0xc8/0xdd0 kernel/bpf/lpm_trie.c:324 > > 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+0x3a/0x60 kernel/locking/spinlock.c:162 > trie_delete_elem+0xb0/0x7e0 kernel/bpf/lpm_trie.c:451 > ___bpf_prog_run+0x3e51/0xabd0 kernel/bpf/core.c:1997 > __bpf_prog_run32+0xc1/0x100 kernel/bpf/core.c:2236 > 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_run2+0x151/0x420 kernel/trace/bpf_trace.c:2420 > __bpf_trace_contention_end+0xca/0x110 include/trace/events/lock.h:122 > trace_contention_end.constprop.0+0xea/0x170 include/trace/events/lock.h:122 > __pv_queued_spin_lock_slowpath+0x266/0xc80 kernel/locking/qspinlock.c:560 > pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:584 [inline] > queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline] > queued_spin_lock include/asm-generic/qspinlock.h:114 [inline] > do_raw_spin_lock+0x210/0x2c0 kernel/locking/spinlock_debug.c:116 > __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:111 [inline] > _raw_spin_lock_irqsave+0x42/0x60 kernel/locking/spinlock.c:162 > rmqueue_bulk mm/page_alloc.c:2131 [inline] > __rmqueue_pcplist+0x5a8/0x1b00 mm/page_alloc.c:2826 > rmqueue_pcplist mm/page_alloc.c:2868 [inline] > rmqueue mm/page_alloc.c:2905 [inline] > get_page_from_freelist+0xbaa/0x3780 mm/page_alloc.c:3314 > __alloc_pages+0x22b/0x2460 mm/page_alloc.c:4575 > __alloc_pages_node include/linux/gfp.h:238 [inline] > alloc_pages_node include/linux/gfp.h:261 [inline] > alloc_slab_page mm/slub.c:2175 [inline] > allocate_slab mm/slub.c:2338 [inline] > new_slab+0xcc/0x3a0 mm/slub.c:2391 > ___slab_alloc+0x66d/0x1790 mm/slub.c:3525 > __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3610 > __slab_alloc_node mm/slub.c:3663 [inline] > slab_alloc_node mm/slub.c:3835 [inline] > __do_kmalloc_node mm/slub.c:3965 [inline] > __kmalloc_node_track_caller+0x367/0x470 mm/slub.c:3986 > kmalloc_reserve+0xef/0x2c0 net/core/skbuff.c:599 > __alloc_skb+0x164/0x380 net/core/skbuff.c:668 > alloc_skb include/linux/skbuff.h:1313 [inline] > nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:748 [inline] > nsim_dev_trap_report drivers/net/netdevsim/dev.c:805 [inline] > nsim_dev_trap_report_work+0x2a4/0xc80 drivers/net/netdevsim/dev.c:850 > process_one_work+0x9a9/0x1ac0 kernel/workqueue.c:3254 > process_scheduled_works kernel/workqueue.c:3335 [inline] > worker_thread+0x6c8/0xf70 kernel/workqueue.c:3416 > kthread+0x2c1/0x3a0 kernel/kthread.c:388 > ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 > > -> #0 (&zone->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+0x2478/0x3b30 kernel/locking/lockdep.c:5137 > lock_acquire kernel/locking/lockdep.c:5754 [inline] > lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719 > __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] > _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162 > rmqueue_buddy mm/page_alloc.c:2730 [inline] > rmqueue mm/page_alloc.c:2911 [inline] > get_page_from_freelist+0x4b9/0x3780 mm/page_alloc.c:3314 > __alloc_pages+0x22b/0x2460 mm/page_alloc.c:4575 > __alloc_pages_node include/linux/gfp.h:238 [inline] > alloc_pages_node include/linux/gfp.h:261 [inline] > __kmalloc_large_node+0x7f/0x1a0 mm/slub.c:3911 > __do_kmalloc_node mm/slub.c:3954 [inline] > __kmalloc_node.cold+0x5/0x5f mm/slub.c:3973 > kmalloc_node include/linux/slab.h:648 [inline] > bpf_map_kmalloc_node+0x98/0x4a0 kernel/bpf/syscall.c:422 > lpm_trie_node_alloc kernel/bpf/lpm_trie.c:291 [inline] > trie_update_elem+0x1ef/0xdd0 kernel/bpf/lpm_trie.c:333 > bpf_map_update_value+0x2c1/0x6c0 kernel/bpf/syscall.c:203 > map_update_elem+0x623/0x910 kernel/bpf/syscall.c:1641 > __sys_bpf+0xab9/0x4b40 kernel/bpf/syscall.c:5648 > __do_sys_bpf kernel/bpf/syscall.c:5767 [inline] > __se_sys_bpf kernel/bpf/syscall.c:5765 [inline] > __x64_sys_bpf+0x78/0xc0 kernel/bpf/syscall.c:5765 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0xcf/0x260 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > other info that might help us debug this: > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(&trie->lock); > lock(&zone->lock); > lock(&trie->lock); > lock(&zone->lock); > > *** DEADLOCK *** > > 2 locks held by syz-executor.2/7645: > #0: ffffffff8d7b0e20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline] > #0: ffffffff8d7b0e20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline] > #0: ffffffff8d7b0e20 (rcu_read_lock){....}-{1:2}, at: bpf_map_update_value+0x24b/0x6c0 kernel/bpf/syscall.c:202 > #1: ffff88802c8739f8 (&trie->lock){-.-.}-{2:2}, at: trie_update_elem+0xc8/0xdd0 kernel/bpf/lpm_trie.c:324 The normal lock sequence is trie->lock and then zone->lock, the syzbot constructs a reversed lock sequence by attaching a bpf program to trace_contention_end() on zone->lock and calls trie_delete_elem() in the bpf program, so the dead-lock is indeed possible. There are two feasible ways to fix the problem: 1) switch from bpf_map_kmalloc_node()/kfree to bpf memory allocator for lpm trie 2) add a dead-lock checking map just like hash-table does and also need to make lockdep be happy with the try-lock mechanism. I prefer 1), but it could not eliminate the dead-lock completely, because the syzbot may construct a bpf program which invokes trie_delete_elem(), attach to trace_contention_end() on trie->lock and leads to a dead-lock, so will fix the syzbot report by 2).
