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Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-2800868f.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/7a4b1a29003d/vmlinux-2800868f.xz kernel image: https://storage.googleapis.com/syzbot-assets/02da498b013d/bzImage-2800868f.xz AI-generated root cause summary: During network namespace destruction, IPVS flushes its virtual services and destinations in __ip_vs_cleanup_batch() via ip_vs_flush() -> __ip_vs_unlink_dest() -> __ip_vs_dst_cache_reset(). When resetting dest->dest_dst, __ip_vs_dst_cache_reset() defers releasing the cached dst_entry via call_rcu(&old->rcu_head, ip_vs_dest_dst_rcu_free). Because IPVS does not invoke rcu_barrier() during netns teardown, earlier-registered pernet subsystem exit handlers (such as ip6_route_net_exit) proceed to tear down the namespace's dst_ops via dst_entries_destroy(), which destroys the percpu counter and sets pcpuc_entries.counters to NULL. When the deferred ip_vs_dest_dst_rcu_free() callback eventually runs in softirq context, dst_release() invokes dst_entries_add() -> percpu_counter_add_batch(), which dereferences the NULL fbc->counters pointer via this_cpu_read() (%gs:0), causing a fatal kernel page fault at the GS segment base address. full analysis: https://syzkaller.appspot.com/x/ai_root_cause?x=84e27adb95fd2a1fe9bb IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+84e27adb95fd2a1fe9bb@syzkaller.appspotmail.com BUG: unable to handle page fault for address: ffff8880d456e000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 1d131067 P4D 1d131067 PUD 0 Oops: Oops: 0000 [#1] SMP KASAN NOPTI CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:percpu_counter_add_batch+0x4b/0x230 lib/percpu_counter.c:98 Code: 8d 45 58 48 89 c2 48 89 44 24 08 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 9f 01 00 00 4d 8b 65 58 4c 89 ff <65> 49 63 2c 24 4a 8d 54 35 00 48 89 6c 24 10 48 89 eb 48 89 d0 48 RSP: 0018:ffffc900006b0d68 EFLAGS: 00010246 RAX: dffffc0000000000 RBX: ffff88803e0cf400 RCX: 0000000000000101 RDX: 1ffff11007045bab RSI: ffffffff85702e00 RDI: 0000000000000020 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000003 R11: 0000000000000001 R12: 0000000000000000 R13: ffff88803822dd00 R14: ffffffffffffffff R15: 0000000000000020 FS: 0000000000000000(0000) GS:ffff8880d456e000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffff8880d456e000 CR3: 0000000025b53000 CR4: 0000000000352ef0 DR0: 0000000000000010 DR1: 00000000fffffffd DR2: 400000000001001d DR3: fffffffffffffff6 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Call Trace: dst_entries_add include/net/dst_ops.h:59 [inline] dst_count_dec net/core/dst.c:163 [inline] dst_count_dec net/core/dst.c:160 [inline] dst_release net/core/dst.c:177 [inline] dst_release+0x2aa/0x330 net/core/dst.c:166 ip_vs_dest_dst_rcu_free+0x32/0x50 net/netfilter/ipvs/ip_vs_ctl.c:1081 rcu_do_batch kernel/rcu/tree.c:2650 [inline] rcu_core+0x5f0/0x1220 kernel/rcu/tree.c:2919 handle_softirqs+0x216/0xa20 kernel/softirq.c:669 __do_softirq kernel/softirq.c:703 [inline] invoke_softirq kernel/softirq.c:542 [inline] __irq_exit_rcu+0x178/0x220 kernel/softirq.c:786 irq_exit_rcu+0x9/0x30 kernel/softirq.c:809 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline] sysvec_apic_timer_interrupt+0xa3/0xc0 arch/x86/kernel/apic/apic.c:1062 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674 RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:64 Code: 56 9f 02 c3 cc cc cc cc 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa eb 07 0f 00 2d 33 4e 1b 00 fb f4 4c 62 03 00 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90 RSP: 0018:ffffc90000187e00 EFLAGS: 00000206 RAX: 00000000009bb6ed RBX: ffff888020abcb00 RCX: ffffffff8bf07375 RDX: 0000000000000001 RSI: ffffffff8e62a27a RDI: ffffffff8c835280 RBP: ffffed1004157960 R08: 0000000000000001 R09: ffffed100d426825 R10: ffff88806a13412b R11: 0000000000000001 R12: 0000000000000000 R13: 0000000000000000 R14: 1ffff92000030fc4 R15: dffffc0000000000 arch_safe_halt arch/x86/include/asm/paravirt.h:62 [inline] default_idle+0x9/0x10 arch/x86/kernel/process.c:768 default_idle_call+0x6c/0xb0 kernel/sched/idle.c:122 cpuidle_idle_call kernel/sched/idle.c:199 [inline] do_idle+0x3ae/0x5b0 kernel/sched/idle.c:355 cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:458 start_secondary+0x21d/0x2d0 arch/x86/kernel/smpboot.c:312 common_startup_64+0x13e/0x158 Modules linked in: CR2: ffff8880d456e000 ---[ end trace 0000000000000000 ]--- RIP: 0010:percpu_counter_add_batch+0x4b/0x230 lib/percpu_counter.c:98 Code: 8d 45 58 48 89 c2 48 89 44 24 08 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 9f 01 00 00 4d 8b 65 58 4c 89 ff <65> 49 63 2c 24 4a 8d 54 35 00 48 89 6c 24 10 48 89 eb 48 89 d0 48 RSP: 0018:ffffc900006b0d68 EFLAGS: 00010246 RAX: dffffc0000000000 RBX: ffff88803e0cf400 RCX: 0000000000000101 RDX: 1ffff11007045bab RSI: ffffffff85702e00 RDI: 0000000000000020 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000003 R11: 0000000000000001 R12: 0000000000000000 R13: ffff88803822dd00 R14: ffffffffffffffff R15: 0000000000000020 FS: 0000000000000000(0000) GS:ffff8880d456e000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffff8880d456e000 CR3: 0000000025b53000 CR4: 0000000000352ef0 DR0: 0000000000000010 DR1: 00000000fffffffd DR2: 400000000001001d DR3: fffffffffffffff6 DR6: 00000000ffff0ff0 DR7: 0000000000000400 ---------------- Code disassembly (best guess): 0: 8d 45 58 lea 0x58(%rbp),%eax 3: 48 89 c2 mov %rax,%rdx 6: 48 89 44 24 08 mov %rax,0x8(%rsp) b: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax 12: fc ff df 15: 48 c1 ea 03 shr $0x3,%rdx 19: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) 1d: 0f 85 9f 01 00 00 jne 0x1c2 23: 4d 8b 65 58 mov 0x58(%r13),%r12 27: 4c 89 ff mov %r15,%rdi * 2a: 65 49 63 2c 24 movslq %gs:(%r12),%rbp <-- trapping instruction 2f: 4a 8d 54 35 00 lea 0x0(%rbp,%r14,1),%rdx 34: 48 89 6c 24 10 mov %rbp,0x10(%rsp) 39: 48 89 eb mov %rbp,%rbx 3c: 48 89 d0 mov %rdx,%rax 3f: 48 rex.W --- This report is generated by a bot. 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