Hello, syzbot found the following crash on: HEAD commit: 2019fc96 Merge git://git.kernel.org/pub/scm/linux/kernel/g.. git tree: net console output: https://syzkaller.appspot.com/x/log.txt?x=1085b209e00000 kernel config: https://syzkaller.appspot.com/x/.config?x=735296e4dd620b10 dashboard link: https://syzkaller.appspot.com/bug?extid=a38ff3d9356388f2fb83 compiler: gcc (GCC) 9.0.0 20181231 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14d716e6e00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1485b209e00000 The bug was bisected to: commit 057996380a42bb64ccc04383cfa9c0ace4ea11f0 Author: Yonghong Song <yhs@xxxxxx> Date: Wed Jan 15 18:43:04 2020 +0000 bpf: Add batch ops to all htab bpf map bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14d9b6e6e00000 final crash: https://syzkaller.appspot.com/x/report.txt?x=16d9b6e6e00000 console output: https://syzkaller.appspot.com/x/log.txt?x=12d9b6e6e00000 IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+a38ff3d9356388f2fb83@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: 057996380a42 ("bpf: Add batch ops to all htab bpf map") ====================================================== WARNING: possible circular locking dependency detected 5.6.0-rc1-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor432/10129 is trying to acquire lock: ffff8880988693e0 (&htab->buckets[i].lock){....}, at: htab_lru_map_delete_node+0xce/0x2f0 kernel/bpf/hashtab.c:593 but task is already holding lock: ffff888098869a18 (&l->lock){....}, at: bpf_lru_list_pop_free_to_local kernel/bpf/bpf_lru_list.c:325 [inline] ffff888098869a18 (&l->lock){....}, at: bpf_common_lru_pop_free kernel/bpf/bpf_lru_list.c:447 [inline] ffff888098869a18 (&l->lock){....}, at: bpf_lru_pop_free+0x67f/0x1670 kernel/bpf/bpf_lru_list.c:499 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&l->lock){....}: __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:151 bpf_lru_list_pop_free_to_local kernel/bpf/bpf_lru_list.c:325 [inline] bpf_common_lru_pop_free kernel/bpf/bpf_lru_list.c:447 [inline] bpf_lru_pop_free+0x67f/0x1670 kernel/bpf/bpf_lru_list.c:499 prealloc_lru_pop+0x2c/0xa0 kernel/bpf/hashtab.c:132 __htab_lru_percpu_map_update_elem+0x67e/0xa90 kernel/bpf/hashtab.c:1069 bpf_percpu_hash_update+0x16e/0x210 kernel/bpf/hashtab.c:1585 bpf_map_update_value.isra.0+0x2d7/0x8e0 kernel/bpf/syscall.c:181 generic_map_update_batch+0x41f/0x610 kernel/bpf/syscall.c:1319 bpf_map_do_batch+0x3f5/0x510 kernel/bpf/syscall.c:3348 __do_sys_bpf+0x9b7/0x41e0 kernel/bpf/syscall.c:3460 __se_sys_bpf kernel/bpf/syscall.c:3355 [inline] __x64_sys_bpf+0x73/0xb0 kernel/bpf/syscall.c:3355 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (&loc_l->lock){....}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:159 bpf_common_lru_push_free kernel/bpf/bpf_lru_list.c:516 [inline] bpf_lru_push_free+0x250/0x5b0 kernel/bpf/bpf_lru_list.c:555 __htab_map_lookup_and_delete_batch+0x8d4/0x1540 kernel/bpf/hashtab.c:1374 htab_lru_map_lookup_and_delete_batch+0x34/0x40 kernel/bpf/hashtab.c:1491 bpf_map_do_batch+0x3f5/0x510 kernel/bpf/syscall.c:3348 __do_sys_bpf+0x1f7d/0x41e0 kernel/bpf/syscall.c:3456 __se_sys_bpf kernel/bpf/syscall.c:3355 [inline] __x64_sys_bpf+0x73/0xb0 kernel/bpf/syscall.c:3355 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&htab->buckets[i].lock){....}: check_prev_add kernel/locking/lockdep.c:2475 [inline] check_prevs_add kernel/locking/lockdep.c:2580 [inline] validate_chain kernel/locking/lockdep.c:2970 [inline] __lock_acquire+0x2596/0x4a00 kernel/locking/lockdep.c:3954 lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4484 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:159 htab_lru_map_delete_node+0xce/0x2f0 kernel/bpf/hashtab.c:593 __bpf_lru_list_shrink_inactive kernel/bpf/bpf_lru_list.c:220 [inline] __bpf_lru_list_shrink+0xf9/0x470 kernel/bpf/bpf_lru_list.c:266 bpf_lru_list_pop_free_to_local kernel/bpf/bpf_lru_list.c:340 [inline] bpf_common_lru_pop_free kernel/bpf/bpf_lru_list.c:447 [inline] bpf_lru_pop_free+0x87c/0x1670 kernel/bpf/bpf_lru_list.c:499 prealloc_lru_pop+0x2c/0xa0 kernel/bpf/hashtab.c:132 __htab_lru_percpu_map_update_elem+0x67e/0xa90 kernel/bpf/hashtab.c:1069 bpf_percpu_hash_update+0x16e/0x210 kernel/bpf/hashtab.c:1585 bpf_map_update_value.isra.0+0x2d7/0x8e0 kernel/bpf/syscall.c:181 generic_map_update_batch+0x41f/0x610 kernel/bpf/syscall.c:1319 bpf_map_do_batch+0x3f5/0x510 kernel/bpf/syscall.c:3348 __do_sys_bpf+0x9b7/0x41e0 kernel/bpf/syscall.c:3460 __se_sys_bpf kernel/bpf/syscall.c:3355 [inline] __x64_sys_bpf+0x73/0xb0 kernel/bpf/syscall.c:3355 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: &htab->buckets[i].lock --> &loc_l->lock --> &l->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&l->lock); lock(&loc_l->lock); lock(&l->lock); lock(&htab->buckets[i].lock); *** DEADLOCK *** 3 locks held by syz-executor432/10129: #0: ffffffff89bac240 (rcu_read_lock){....}, at: bpf_percpu_hash_update+0x0/0x210 kernel/bpf/hashtab.c:1565 #1: ffffe8ffffc49e40 (&loc_l->lock){....}, at: bpf_common_lru_pop_free kernel/bpf/bpf_lru_list.c:443 [inline] #1: ffffe8ffffc49e40 (&loc_l->lock){....}, at: bpf_lru_pop_free+0x32b/0x1670 kernel/bpf/bpf_lru_list.c:499 #2: ffff888098869a18 (&l->lock){....}, at: bpf_lru_list_pop_free_to_local kernel/bpf/bpf_lru_list.c:325 [inline] #2: ffff888098869a18 (&l->lock){....}, at: bpf_common_lru_pop_free kernel/bpf/bpf_lru_list.c:447 [inline] #2: ffff888098869a18 (&l->lock){....}, at: bpf_lru_pop_free+0x67f/0x1670 kernel/bpf/bpf_lru_list.c:499 stack backtrace: CPU: 0 PID: 10129 Comm: syz-executor432 Not tainted 5.6.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x197/0x210 lib/dump_stack.c:118 print_circular_bug.isra.0.cold+0x163/0x172 kernel/locking/lockdep.c:1684 check_noncircular+0x32e/0x3e0 kernel/locking/lockdep.c:1808 check_prev_add kernel/locking/lockdep.c:2475 [inline] check_prevs_add kernel/locking/lockdep.c:2580 [inline] validate_chain kernel/locking/lockdep.c:2970 [inline] __lock_acquire+0x2596/0x4a00 kernel/locking/lockdep.c:3954 lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4484 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:159 htab_lru_map_delete_node+0xce/0x2f0 kernel/bpf/hashtab.c:593 __bpf_lru_list_shrink_inactive kernel/bpf/bpf_lru_list.c:220 [inline] __bpf_lru_list_shrink+0xf9/0x470 kernel/bpf/bpf_lru_list.c:266 bpf_lru_list_pop_free_to_local kernel/bpf/bpf_lru_list.c:340 [inline] bpf_common_lru_pop_free kernel/bpf/bpf_lru_list.c:447 [inline] bpf_lru_pop_free+0x87c/0x1670 kernel/bpf/bpf_lru_list.c:499 prealloc_lru_pop+0x2c/0xa0 kernel/bpf/hashtab.c:132 __htab_lru_percpu_map_update_elem+0x67e/0xa90 kernel/bpf/hashtab.c:1069 bpf_percpu_hash_update+0x16e/0x210 kernel/bpf/hashtab.c:1585 bpf_map_update_value.isra.0+0x2d7/0x8e0 kernel/bpf/syscall.c:181 generic_map_update_batch+0x41f/0x610 kernel/bpf/syscall.c:1319 bpf_map_do_batch+0x3f5/0x510 kernel/bpf/syscall.c:3348 __do_sys_bpf+0x9b7/0x41e0 kernel/bpf/syscall.c:3460 __se_sys_bpf kernel/bpf/syscall.c:3355 [inline] __x64_sys_bpf+0x73/0xb0 kernel/bpf/syscall.c:3355 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x446b99 Code: e8 bc b4 02 00 48 83 c4 18 c3 0f 1f 80 00 00 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 0f 83 ab 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f14c0df8db8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141 RAX: ffffffffffffffda RBX: 00000000006dbc28 RCX: 0000000000446b99 RDX: 0000000000000038 RSI: 0000000020000040 RDI: 000000000000001a RBP: 00000000006dbc20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc2c R13: 00007ffc51c1364f R14: 00007f14c0df99c0 R15: 0000000000000000 --- This bug is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. syzbot will keep track of this bug report. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. For information about bisection process see: https://goo.gl/tpsmEJ#bisection syzbot can test patches for this bug, for details see: https://goo.gl/tpsmEJ#testing-patches