On 26/8/25 01:39, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: dd9de524183a xsk: Fix immature cq descriptor production > git tree: bpf > console output: https://syzkaller.appspot.com/x/log.txt?x=102da862580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=c321f33e4545e2a1 > dashboard link: https://syzkaller.appspot.com/bug?extid=fa5c2814795b5adca240 > compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=142da862580000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1588aef0580000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/5a3389c1558f/disk-dd9de524.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/c97133192a27/vmlinux-dd9de524.xz > kernel image: https://storage.googleapis.com/syzbot-assets/3ae5a1a88637/bzImage-dd9de524.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+fa5c2814795b5adca240@xxxxxxxxxxxxxxxxxxxxxxxxx > > ============================================ > WARNING: possible recursive locking detected > syzkaller #0 Not tainted > -------------------------------------------- > syz-execprog/5866 is trying to acquire lock: > ffffc900048c10d8 (&rb->spinlock){-.-.}-{2:2}, at: __bpf_ringbuf_reserve+0x1c7/0x5a0 kernel/bpf/ringbuf.c:423 > > but task is already holding lock: > ffffc900048e90d8 (&rb->spinlock){-.-.}-{2:2}, at: __bpf_ringbuf_reserve+0x1c7/0x5a0 kernel/bpf/ringbuf.c:423 > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(&rb->spinlock); > lock(&rb->spinlock); > > *** DEADLOCK *** > > May be due to missing lock nesting notation Confirmed. I can reproduce this deadlock issue and will work on a fix. Thanks, Leon > > 6 locks held by syz-execprog/5866: > #0: ffff88807e021588 (vm_lock){++++}-{0:0}, at: lock_vma_under_rcu+0x19f/0x3d0 mm/mmap_lock.c:147 > #1: ffffffff8e139ea0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] > #1: ffffffff8e139ea0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] > #1: ffffffff8e139ea0 (rcu_read_lock){....}-{1:3}, at: ___pte_offset_map+0x29/0x250 mm/pgtable-generic.c:286 > #2: ffff8880787b60d8 (ptlock_ptr(ptdesc)#2){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline] > #2: ffff8880787b60d8 (ptlock_ptr(ptdesc)#2){+.+.}-{3:3}, at: __pte_offset_map_lock+0x13e/0x210 mm/pgtable-generic.c:401 > #3: ffffffff8e139ea0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] > #3: ffffffff8e139ea0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] > #3: ffffffff8e139ea0 (rcu_read_lock){....}-{1:3}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2256 [inline] > #3: ffffffff8e139ea0 (rcu_read_lock){....}-{1:3}, at: bpf_trace_run2+0x186/0x4b0 kernel/trace/bpf_trace.c:2298 > #4: ffffc900048e90d8 (&rb->spinlock){-.-.}-{2:2}, at: __bpf_ringbuf_reserve+0x1c7/0x5a0 kernel/bpf/ringbuf.c:423 > #5: ffffffff8e139ea0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] > #5: ffffffff8e139ea0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] > #5: ffffffff8e139ea0 (rcu_read_lock){....}-{1:3}, at: trace_call_bpf+0xb7/0x850 kernel/trace/bpf_trace.c:-1 > > stack backtrace: > CPU: 1 UID: 0 PID: 5866 Comm: syz-execprog Not tainted syzkaller #0 PREEMPT(full) > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 > Call Trace: > <TASK> > dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 > print_deadlock_bug+0x28b/0x2a0 kernel/locking/lockdep.c:3041 > check_deadlock kernel/locking/lockdep.c:3093 [inline] > validate_chain+0x1a3f/0x2140 kernel/locking/lockdep.c:3895 > __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 > lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 > __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] > _raw_spin_lock_irqsave+0xa7/0xf0 kernel/locking/spinlock.c:162 > __bpf_ringbuf_reserve+0x1c7/0x5a0 kernel/bpf/ringbuf.c:423 > ____bpf_ringbuf_reserve kernel/bpf/ringbuf.c:474 [inline] > bpf_ringbuf_reserve+0x5c/0x70 kernel/bpf/ringbuf.c:466 > bpf_prog_df2ea1bb7efca089+0x36/0x54 > bpf_dispatcher_nop_func include/linux/bpf.h:1332 [inline] > __bpf_prog_run include/linux/filter.h:718 [inline] > bpf_prog_run include/linux/filter.h:725 [inline] > bpf_prog_run_array include/linux/bpf.h:2292 [inline] > trace_call_bpf+0x326/0x850 kernel/trace/bpf_trace.c:146 > perf_trace_run_bpf_submit+0x78/0x170 kernel/events/core.c:10911 > do_perf_trace_contention_end include/trace/events/lock.h:122 [inline] > perf_trace_contention_end+0x253/0x2f0 include/trace/events/lock.h:122 > __do_trace_contention_end include/trace/events/lock.h:122 [inline] > trace_contention_end+0x111/0x140 include/trace/events/lock.h:122 > __pv_queued_spin_lock_slowpath+0x9f9/0xb60 kernel/locking/qspinlock.c:374 > pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:557 [inline] > queued_spin_lock_slowpath+0x43/0x50 arch/x86/include/asm/qspinlock.h:51 > queued_spin_lock include/asm-generic/qspinlock.h:114 [inline] > do_raw_spin_lock+0x21f/0x290 kernel/locking/spinlock_debug.c:116 > __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:111 [inline] > _raw_spin_lock_irqsave+0xb3/0xf0 kernel/locking/spinlock.c:162 > __bpf_ringbuf_reserve+0x1c7/0x5a0 kernel/bpf/ringbuf.c:423 > ____bpf_ringbuf_reserve kernel/bpf/ringbuf.c:474 [inline] > bpf_ringbuf_reserve+0x5c/0x70 kernel/bpf/ringbuf.c:466 > bpf_prog_6979e45824a16319+0x36/0x66 > bpf_dispatcher_nop_func include/linux/bpf.h:1332 [inline] > __bpf_prog_run include/linux/filter.h:718 [inline] > bpf_prog_run include/linux/filter.h:725 [inline] > __bpf_trace_run kernel/trace/bpf_trace.c:2257 [inline] > bpf_trace_run2+0x281/0x4b0 kernel/trace/bpf_trace.c:2298 > __bpf_trace_tlb_flush+0xf5/0x150 include/trace/events/tlb.h:38 > __traceiter_tlb_flush+0x76/0xd0 include/trace/events/tlb.h:38 > __do_trace_tlb_flush include/trace/events/tlb.h:38 [inline] > trace_tlb_flush+0x115/0x140 include/trace/events/tlb.h:38 > native_flush_tlb_multi+0x78/0x140 arch/x86/mm/tlb.c:-1 > __flush_tlb_multi arch/x86/include/asm/paravirt.h:91 [inline] > flush_tlb_multi arch/x86/mm/tlb.c:1361 [inline] > flush_tlb_mm_range+0x6b1/0x12d0 arch/x86/mm/tlb.c:1451 > flush_tlb_page arch/x86/include/asm/tlbflush.h:324 [inline] > ptep_clear_flush+0x120/0x170 mm/pgtable-generic.c:101 > wp_page_copy mm/memory.c:3618 [inline] > do_wp_page+0x1bc2/0x5800 mm/memory.c:4013 > handle_pte_fault mm/memory.c:6068 [inline] > __handle_mm_fault+0x1033/0x5440 mm/memory.c:6195 > handle_mm_fault+0x40a/0x8e0 mm/memory.c:6364 > do_user_addr_fault+0xa81/0x1390 arch/x86/mm/fault.c:1336 > handle_page_fault arch/x86/mm/fault.c:1476 [inline] > exc_page_fault+0x76/0xf0 arch/x86/mm/fault.c:1532 > asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623 > RIP: 0033:0x410964 > Code: b9 01 00 00 00 90 e8 3b 36 06 00 84 00 48 8d 50 10 83 3d be 5f d9 02 00 74 10 e8 87 d9 06 00 49 89 13 48 8b 48 10 49 89 4b 08 <48> 89 50 10 48 89 c1 48 8b 54 24 20 48 8b 1a 66 89 59 18 83 3d 92 > RSP: 002b:000000c0000e7608 EFLAGS: 00010246 > RAX: 000000c0080e0000 RBX: 0000000000000070 RCX: 0000000007b2a8a0 > RDX: 000000c0080e0010 RSI: 000000000b1130e1 RDI: 0000000009e14d67 > RBP: 000000c0000e7638 R08: 00007f16e8ad96e0 R09: 7fffffffffffffff > R10: 0000000000000001 R11: 00007f16e8a2e000 R12: 000000c0080e0000 > R13: 0000000000000049 R14: 000000c0026156c0 R15: 000000c0080c1c20 > </TASK> > > > --- > This report 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 issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > If the report is already addressed, let syzbot know by replying with: > #syz fix: exact-commit-title > > If you want syzbot to run the reproducer, reply with: > #syz test: git://repo/address.git branch-or-commit-hash > If you attach or paste a git patch, syzbot will apply it before testing. > > If you want to overwrite report's subsystems, reply with: > #syz set subsystems: new-subsystem > (See the list of subsystem names on the web dashboard) > > If the report is a duplicate of another one, reply with: > #syz dup: exact-subject-of-another-report > > If you want to undo deduplication, reply with: > #syz undup >
