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Multiple syzbot warnings have been reported. These warnings are mainly about the lock order between trie->lock and kmalloc()'s internal lock. See report [1] as an example: ====================================================== WARNING: possible circular locking dependency detected 6.10.0-rc7-syzkaller-00003-g4376e966ecb7 #0 Not tainted ------------------------------------------------------ syz.3.2069/15008 is trying to acquire lock: ffff88801544e6d8 (&n->list_lock){-.-.}-{2:2}, at: get_partial_node ... but task is already holding lock: ffff88802dcc89f8 (&trie->lock){-.-.}-{2:2}, at: trie_update_elem ... 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 _raw_spin_lock_irqsave+0x3a/0x60 trie_delete_elem+0xb0/0x820 ___bpf_prog_run+0x3e51/0xabd0 __bpf_prog_run32+0xc1/0x100 bpf_dispatcher_nop_func ...... bpf_trace_run2+0x231/0x590 __bpf_trace_contention_end+0xca/0x110 trace_contention_end.constprop.0+0xea/0x170 __pv_queued_spin_lock_slowpath+0x28e/0xcc0 pv_queued_spin_lock_slowpath queued_spin_lock_slowpath queued_spin_lock do_raw_spin_lock+0x210/0x2c0 __raw_spin_lock_irqsave _raw_spin_lock_irqsave+0x42/0x60 __put_partials+0xc3/0x170 qlink_free qlist_free_all+0x4e/0x140 kasan_quarantine_reduce+0x192/0x1e0 __kasan_slab_alloc+0x69/0x90 kasan_slab_alloc slab_post_alloc_hook slab_alloc_node kmem_cache_alloc_node_noprof+0x153/0x310 __alloc_skb+0x2b1/0x380 ...... -> #0 (&n->list_lock){-.-.}-{2:2}: check_prev_add check_prevs_add validate_chain __lock_acquire+0x2478/0x3b30 lock_acquire lock_acquire+0x1b1/0x560 __raw_spin_lock_irqsave _raw_spin_lock_irqsave+0x3a/0x60 get_partial_node.part.0+0x20/0x350 get_partial_node get_partial ___slab_alloc+0x65b/0x1870 __slab_alloc.constprop.0+0x56/0xb0 __slab_alloc_node slab_alloc_node __do_kmalloc_node __kmalloc_node_noprof+0x35c/0x440 kmalloc_node_noprof bpf_map_kmalloc_node+0x98/0x4a0 lpm_trie_node_alloc trie_update_elem+0x1ef/0xe00 bpf_map_update_value+0x2c1/0x6c0 map_update_elem+0x623/0x910 __sys_bpf+0x90c/0x49a0 ... other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&trie->lock); lock(&n->list_lock); lock(&trie->lock); lock(&n->list_lock); *** DEADLOCK *** [1]: https://syzkaller.appspot.com/bug?extid=9045c0a3d5a7f1b119f7 A bpf program attached to trace_contention_end() triggers after acquiring &n->list_lock. The program invokes trie_delete_elem(), which then acquires trie->lock. However, it is possible that another process is invoking trie_update_elem(). trie_update_elem() will acquire trie->lock first, then invoke kmalloc_node(). kmalloc_node() may invoke get_partial_node() and try to acquire &n->list_lock (not necessarily the same lock object). Therefore, lockdep warns about the circular locking dependency. Invoking kmalloc() before acquiring trie->lock could fix the warning. However, since BPF programs call be invoked from any context (e.g., through kprobe/tracepoint/fentry), there may still be lock ordering problems for internal locks in kmalloc() or trie->lock itself. To eliminate these potential lock ordering problems with kmalloc()'s internal locks, replacing kmalloc()/kfree()/kfree_rcu() with equivalent BPF memory allocator APIs that can be invoked in any context. The lock ordering problems with trie->lock (e.g., reentrance) will be handled separately. Three aspects of this change require explanation: 1. Intermediate and leaf nodes are allocated from the same allocator. Since the value size of LPM trie is usually small, using a single alocator reduces the memory overhead of the BPF memory allocator. 2. Leaf nodes are allocated before disabling IRQs. This handles cases where leaf_size is large (e.g., > 4KB - 8) and updates require intermediate node allocation. If leaf nodes were allocated in IRQ-disabled region, the free objects in BPF memory allocator would not be refilled timely and the intermediate node allocation may fail. 3. Paired migrate_{disable|enable}() calls for node alloc and free. The BPF memory allocator uses per-CPU struct internally, these paired calls are necessary to guarantee correctness. Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com> Signed-off-by: Hou Tao <houtao1@huawei.com> Link: https://lore.kernel.org/r/20241206110622.1161752-7-houtao@huaweicloud.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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| bpf | ||
| cgroup | ||
| configs | ||
| debug | ||
| dma | ||
| entry | ||
| events | ||
| futex | ||
| gcov | ||
| irq | ||
| kcsan | ||
| livepatch | ||
| locking | ||
| module | ||
| power | ||
| printk | ||
| rcu | ||
| sched | ||
| time | ||
| trace | ||
| .gitignore | ||
| acct.c | ||
| async.c | ||
| audit.c | ||
| audit.h | ||
| audit_fsnotify.c | ||
| audit_tree.c | ||
| audit_watch.c | ||
| auditfilter.c | ||
| auditsc.c | ||
| backtracetest.c | ||
| bounds.c | ||
| capability.c | ||
| cfi.c | ||
| compat.c | ||
| configs.c | ||
| context_tracking.c | ||
| cpu.c | ||
| cpu_pm.c | ||
| crash_core.c | ||
| crash_reserve.c | ||
| cred.c | ||
| delayacct.c | ||
| dma.c | ||
| elfcorehdr.c | ||
| exec_domain.c | ||
| exit.c | ||
| exit.h | ||
| extable.c | ||
| fail_function.c | ||
| fork.c | ||
| freezer.c | ||
| gen_kheaders.sh | ||
| groups.c | ||
| hung_task.c | ||
| iomem.c | ||
| irq_work.c | ||
| jump_label.c | ||
| kallsyms.c | ||
| kallsyms_internal.h | ||
| kallsyms_selftest.c | ||
| kallsyms_selftest.h | ||
| kcmp.c | ||
| Kconfig.freezer | ||
| Kconfig.hz | ||
| Kconfig.kexec | ||
| Kconfig.locks | ||
| Kconfig.preempt | ||
| kcov.c | ||
| kexec.c | ||
| kexec_core.c | ||
| kexec_elf.c | ||
| kexec_file.c | ||
| kexec_internal.h | ||
| kheaders.c | ||
| kprobes.c | ||
| ksyms_common.c | ||
| ksysfs.c | ||
| kthread.c | ||
| latencytop.c | ||
| Makefile | ||
| module_signature.c | ||
| notifier.c | ||
| nsproxy.c | ||
| padata.c | ||
| panic.c | ||
| params.c | ||
| pid.c | ||
| pid_namespace.c | ||
| pid_sysctl.h | ||
| profile.c | ||
| ptrace.c | ||
| range.c | ||
| reboot.c | ||
| regset.c | ||
| relay.c | ||
| resource.c | ||
| resource_kunit.c | ||
| rseq.c | ||
| scftorture.c | ||
| scs.c | ||
| seccomp.c | ||
| signal.c | ||
| smp.c | ||
| smpboot.c | ||
| smpboot.h | ||
| softirq.c | ||
| stackleak.c | ||
| stacktrace.c | ||
| static_call.c | ||
| static_call_inline.c | ||
| stop_machine.c | ||
| sys.c | ||
| sys_ni.c | ||
| sysctl-test.c | ||
| sysctl.c | ||
| task_work.c | ||
| taskstats.c | ||
| torture.c | ||
| tracepoint.c | ||
| tsacct.c | ||
| ucount.c | ||
| uid16.c | ||
| uid16.h | ||
| umh.c | ||
| up.c | ||
| user-return-notifier.c | ||
| user.c | ||
| user_namespace.c | ||
| usermode_driver.c | ||
| utsname.c | ||
| utsname_sysctl.c | ||
| vhost_task.c | ||
| vmcore_info.c | ||
| watch_queue.c | ||
| watchdog.c | ||
| watchdog_buddy.c | ||
| watchdog_perf.c | ||
| workqueue.c | ||
| workqueue_internal.h | ||