Hi, We found a bug in Linux 6.10 using syzkaller. It is possibly a null pointer dereference bug. The bug report is as follows, but unfortunately there is no generated syzkaller reproducer. Bug report: Oops: general protection fault, probably for non-canonical address 0xdffffc0000000007: 0000 [#1] PREEMPT SMP KASAN PTI KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f] CPU: 0 PID: 2893 Comm: kworker/u4:9 Not tainted 6.10.0 #13 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 Workqueue: bat_events batadv_bla_periodic_work RIP: 0010:arpt_do_table+0x2a8/0x1dc0 net/ipv4/netfilter/arp_tables.c:210 Code: 28 00 74 08 48 89 df e8 26 b3 69 f8 48 8b 1b e8 de f9 6c 01 41 89 c6 48 89 9c 24 88 00 00 00 4c 8d 7b 38 4c 89 f8 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 ff e8 f9 b2 69 f8 44 89 f3 48 c1 e3 03 RSP: 0000:ffffc900000076c0 EFLAGS: 00010202 RAX: 0000000000000007 RBX: 0000000000000000 RCX: ffffffff8c7668e0 RDX: 0000000080000101 RSI: ffffffff8ba956c0 RDI: ffffffff8ba95680 RBP: ffffc900000078a8 R08: ffffffff898aa86c R09: 0000000000000000 R10: ffffc90000007820 R11: ffffffff898aa6d0 R12: ffffc90000007960 R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000038 FS: 0000000000000000(0000) GS:ffff888063a00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffb61bfff40 CR3: 000000000d932000 CR4: 0000000000350ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <IRQ> nf_hook_entry_hookfn include/linux/netfilter.h:154 [inline] nf_hook_slow+0xc0/0x210 net/netfilter/core.c:626 nf_hook+0x2be/0x450 include/linux/netfilter.h:269 NF_HOOK include/linux/netfilter.h:312 [inline] arp_rcv+0x304/0x500 net/ipv4/arp.c:989 __netif_receive_skb_one_core net/core/dev.c:5625 [inline] __netif_receive_skb+0x2cf/0x640 net/core/dev.c:5739 process_backlog+0x37d/0x7a0 net/core/dev.c:6068 __napi_poll+0xcc/0x480 net/core/dev.c:6722 napi_poll net/core/dev.c:6791 [inline] net_rx_action+0x7ed/0x1040 net/core/dev.c:6907 handle_softirqs+0x272/0x750 kernel/softirq.c:554 do_softirq+0x117/0x1e0 kernel/softirq.c:455 </IRQ> <TASK> __local_bh_enable_ip+0x1b0/0x1f0 kernel/softirq.c:382 local_bh_enable include/linux/bottom_half.h:33 [inline] netif_rx+0x7f/0x90 net/core/dev.c:5210 batadv_bla_send_claim+0x827/0xc60 net/batman-adv/bridge_loop_avoidance.c:447 batadv_bla_send_announce net/batman-adv/bridge_loop_avoidance.c:675 [inline] batadv_bla_periodic_work+0x598/0xa80 net/batman-adv/bridge_loop_avoidance.c:1481 process_one_work kernel/workqueue.c:3248 [inline] process_scheduled_works+0x977/0x1410 kernel/workqueue.c:3329 worker_thread+0xaa0/0x1020 kernel/workqueue.c:3409 kthread+0x2eb/0x380 kernel/kthread.c:389 ret_from_fork+0x49/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:244 </TASK> Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:arpt_do_table+0x2a8/0x1dc0 net/ipv4/netfilter/arp_tables.c:210 Code: 28 00 74 08 48 89 df e8 26 b3 69 f8 48 8b 1b e8 de f9 6c 01 41 89 c6 48 89 9c 24 88 00 00 00 4c 8d 7b 38 4c 89 f8 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 ff e8 f9 b2 69 f8 44 89 f3 48 c1 e3 03 RSP: 0000:ffffc900000076c0 EFLAGS: 00010202 RAX: 0000000000000007 RBX: 0000000000000000 RCX: ffffffff8c7668e0 RDX: 0000000080000101 RSI: ffffffff8ba956c0 RDI: ffffffff8ba95680 RBP: ffffc900000078a8 R08: ffffffff898aa86c R09: 0000000000000000 R10: ffffc90000007820 R11: ffffffff898aa6d0 R12: ffffc90000007960 R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000038 FS: 0000000000000000(0000) GS:ffff888063a00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffb61bfff40 CR3: 000000000d932000 CR4: 0000000000350ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 ---------------- Code disassembly (best guess): 0: 28 00 sub %al,(%rax) 2: 74 08 je 0xc 4: 48 89 df mov %rbx,%rdi 7: e8 26 b3 69 f8 call 0xf869b332 c: 48 8b 1b mov (%rbx),%rbx f: e8 de f9 6c 01 call 0x16cf9f2 14: 41 89 c6 mov %eax,%r14d 17: 48 89 9c 24 88 00 00 mov %rbx,0x88(%rsp) 1e: 00 1f: 4c 8d 7b 38 lea 0x38(%rbx),%r15 23: 4c 89 f8 mov %r15,%rax 26: 48 c1 e8 03 shr $0x3,%rax * 2a: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1) <-- trapping instruction 2f: 74 08 je 0x39 31: 4c 89 ff mov %r15,%rdi 34: e8 f9 b2 69 f8 call 0xf869b332 39: 44 89 f3 mov %r14d,%ebx 3c: 48 c1 e3 03 shl $0x3,%rbx -- Yours sincerely, Xingyu
