On Sun, Sep 04, 2022 at 02:21:23PM -0700, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 7fd22855300e Add linux-next specific files for 20220831 > git tree: linux-next > console+strace: https://syzkaller.appspot.com/x/log.txt?x=14e5668b080000 > kernel config: https://syzkaller.appspot.com/x/.config?x=3e56c1a274c93753 > dashboard link: https://syzkaller.appspot.com/bug?extid=2251879aa068ad9c960d > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17dc728b080000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=164748d7080000 > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+2251879aa068ad9c960d@xxxxxxxxxxxxxxxxxxxxxxxxx > > ------------[ cut here ]------------ > WARNING: CPU: 1 PID: 3601 at kernel/bpf/helpers.c:769 try_get_fmt_tmp_buf kernel/bpf/helpers.c:769 [inline] > WARNING: CPU: 1 PID: 3601 at kernel/bpf/helpers.c:769 bpf_bprintf_prepare+0xf31/0x11a0 kernel/bpf/helpers.c:817 > Modules linked in: > CPU: 1 PID: 3601 Comm: strace-static-x Not tainted 6.0.0-rc3-next-20220831-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022 > RIP: 0010:try_get_fmt_tmp_buf kernel/bpf/helpers.c:769 [inline] > RIP: 0010:bpf_bprintf_prepare+0xf31/0x11a0 kernel/bpf/helpers.c:817 > Code: ff e8 93 9f ea ff 48 83 7c 24 08 00 41 bd 04 00 00 00 0f 85 8a fa ff ff e8 7c 9f ea ff 8d 6b 03 e9 f7 f6 ff ff e8 6f 9f ea ff <0f> 0b 65 ff 0d 8e ba 71 7e bf 01 00 00 00 41 bc f0 ff ff ff e8 16 > RSP: 0018:ffffc90003cfeb70 EFLAGS: 00010093 > RAX: 0000000000000000 RBX: 0000000000000002 RCX: 0000000000000000 > RDX: ffff8880219b3a80 RSI: ffffffff819186b1 RDI: 0000000000000005 > RBP: ffffc90003cfeca0 R08: 0000000000000005 R09: 0000000000000003 > R10: 0000000000000004 R11: 0000000000000001 R12: 0000000000000003 > R13: 0000000000000004 R14: ffffc90003cfed58 R15: 0000000000000003 > FS: 0000000001655340(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000020003000 CR3: 0000000074d58000 CR4: 00000000003506e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > <TASK> > ____bpf_trace_printk kernel/trace/bpf_trace.c:383 [inline] > bpf_trace_printk+0xab/0x170 kernel/trace/bpf_trace.c:374 > bpf_prog_0605f9f479290f07+0x2f/0x33 > bpf_dispatcher_nop_func include/linux/bpf.h:904 [inline] > __bpf_prog_run include/linux/filter.h:594 [inline] > bpf_prog_run include/linux/filter.h:601 [inline] > __bpf_trace_run kernel/trace/bpf_trace.c:2046 [inline] > bpf_trace_run2+0x110/0x340 kernel/trace/bpf_trace.c:2083 > __bpf_trace_contention_begin+0xb5/0xf0 include/trace/events/lock.h:95 > trace_contention_begin.constprop.0+0xda/0x1b0 include/trace/events/lock.h:95 > __pv_queued_spin_lock_slowpath+0x103/0xb50 kernel/locking/qspinlock.c:405 > pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:591 [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+0x200/0x2a0 kernel/locking/spinlock_debug.c:115 > __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:111 [inline] > _raw_spin_lock_irqsave+0x41/0x50 kernel/locking/spinlock.c:162 > ____bpf_trace_printk kernel/trace/bpf_trace.c:388 [inline] > bpf_trace_printk+0xcf/0x170 kernel/trace/bpf_trace.c:374 > bpf_prog_0605f9f479290f07+0x2f/0x33 > bpf_dispatcher_nop_func include/linux/bpf.h:904 [inline] > __bpf_prog_run include/linux/filter.h:594 [inline] > bpf_prog_run include/linux/filter.h:601 [inline] > __bpf_trace_run kernel/trace/bpf_trace.c:2046 [inline] > bpf_trace_run2+0x110/0x340 kernel/trace/bpf_trace.c:2083 > __bpf_trace_contention_begin+0xb5/0xf0 include/trace/events/lock.h:95 > trace_contention_begin.constprop.0+0xda/0x1b0 include/trace/events/lock.h:95 > __pv_queued_spin_lock_slowpath+0x103/0xb50 kernel/locking/qspinlock.c:405 > pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:591 [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+0x200/0x2a0 kernel/locking/spinlock_debug.c:115 > __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:111 [inline] > _raw_spin_lock_irqsave+0x41/0x50 kernel/locking/spinlock.c:162 > ____bpf_trace_printk kernel/trace/bpf_trace.c:388 [inline] > bpf_trace_printk+0xcf/0x170 kernel/trace/bpf_trace.c:374 > bpf_prog_0605f9f479290f07+0x2f/0x33 > bpf_dispatcher_nop_func include/linux/bpf.h:904 [inline] > __bpf_prog_run include/linux/filter.h:594 [inline] > bpf_prog_run include/linux/filter.h:601 [inline] > __bpf_trace_run kernel/trace/bpf_trace.c:2046 [inline] > bpf_trace_run2+0x110/0x340 kernel/trace/bpf_trace.c:2083 > __bpf_trace_contention_begin+0xb5/0xf0 include/trace/events/lock.h:95 > trace_contention_begin.constprop.0+0xda/0x1b0 include/trace/events/lock.h:95 > __pv_queued_spin_lock_slowpath+0x103/0xb50 kernel/locking/qspinlock.c:405 > pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:591 [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+0x200/0x2a0 kernel/locking/spinlock_debug.c:115 > __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:111 [inline] > _raw_spin_lock_irqsave+0x41/0x50 kernel/locking/spinlock.c:162 > ____bpf_trace_printk kernel/trace/bpf_trace.c:388 [inline] > bpf_trace_printk+0xcf/0x170 kernel/trace/bpf_trace.c:374 > bpf_prog_0605f9f479290f07+0x2f/0x33 > bpf_dispatcher_nop_func include/linux/bpf.h:904 [inline] > __bpf_prog_run include/linux/filter.h:594 [inline] > bpf_prog_run include/linux/filter.h:601 [inline] > __bpf_trace_run kernel/trace/bpf_trace.c:2046 [inline] > bpf_trace_run2+0x110/0x340 kernel/trace/bpf_trace.c:2083 > __bpf_trace_contention_begin+0xb5/0xf0 include/trace/events/lock.h:95 > trace_contention_begin+0xc0/0x150 include/trace/events/lock.h:95 > __mutex_lock_common kernel/locking/mutex.c:605 [inline] > __mutex_lock+0x13c/0x1350 kernel/locking/mutex.c:747 > __pipe_lock fs/pipe.c:103 [inline] > pipe_write+0x132/0x1be0 fs/pipe.c:431 > call_write_iter include/linux/fs.h:2188 [inline] > new_sync_write fs/read_write.c:491 [inline] > vfs_write+0x9e9/0xdd0 fs/read_write.c:578 > ksys_write+0x1e8/0x250 fs/read_write.c:631 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd looks like __bpf_trace_contention_begin needs bpf_prog_active check (like below untested), which would prevent the recursion and bail out after 2nd invocation should be easy to reproduce, will check jirka --- diff --git a/include/trace/bpf_probe.h b/include/trace/bpf_probe.h index 6a13220d2d27..481b057cc8d9 100644 --- a/include/trace/bpf_probe.h +++ b/include/trace/bpf_probe.h @@ -4,6 +4,8 @@ #ifdef CONFIG_BPF_EVENTS +DECLARE_PER_CPU(int, bpf_prog_active); + #undef __entry #define __entry entry @@ -82,7 +84,11 @@ static notrace void \ __bpf_trace_##call(void *__data, proto) \ { \ struct bpf_prog *prog = __data; \ + if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) \ + goto out; \ CONCATENATE(bpf_trace_run, COUNT_ARGS(args))(prog, CAST_TO_U64(args)); \ +out: \ + __this_cpu_dec(bpf_prog_active); \ } #undef DECLARE_EVENT_CLASS
