netlink: 4 bytes leftover after parsing attributes in process `syz.2.8265'. ================================================================== BUG: KASAN: slab-use-after-free in ip_check_mc_rcu+0x28e/0x680 net/ipv4/igmp.c:2821 Read of size 4 at addr ffff888079159808 by task syz.2.8265/4205 CPU: 1 UID: 0 PID: 4205 Comm: syz.2.8265 Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xba/0x230 mm/kasan/report.c:482 kasan_report+0x117/0x150 mm/kasan/report.c:595 ip_check_mc_rcu+0x28e/0x680 net/ipv4/igmp.c:2821 __mkroute_output net/ipv4/route.c:2603 [inline] ip_route_output_key_hash_rcu+0xe7e/0x25d0 net/ipv4/route.c:2875 ip_route_output_key_hash+0x18d/0x2a0 net/ipv4/route.c:2705 __ip_route_output_key include/net/route.h:169 [inline] ip_route_output_flow+0x2a/0x150 net/ipv4/route.c:2932 udp_sendmsg+0x154a/0x22f0 net/ipv4/udp.c:1451 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg net/socket.c:742 [inline] ____sys_sendmsg+0x894/0xad0 net/socket.c:2592 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2646 __sys_sendmmsg+0x2e7/0x4e0 net/socket.c:2728 __compat_sys_sendmmsg net/compat.c:360 [inline] __do_compat_sys_sendmmsg net/compat.c:367 [inline] __se_compat_sys_sendmmsg net/compat.c:364 [inline] __ia32_compat_sys_sendmmsg+0xa2/0xc0 net/compat.c:364 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline] __do_fast_syscall_32+0x20d/0x640 arch/x86/entry/syscall_32.c:307 do_fast_syscall_32+0x33/0x70 arch/x86/entry/syscall_32.c:332 entry_SYSENTER_compat_after_hwframe+0x84/0x8e RIP: 0023:0xf7f35f6c Code: 90 85 d2 74 0a 89 ce 81 e6 ff 0f 00 00 89 32 85 c0 74 05 c1 e9 0c 89 08 31 c0 5e 5d c3 90 0f 1f 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 58 b8 77 00 00 00 cd 80 0f 0b 90 90 90 90 90 90 b8 ad RSP: 002b:00000000f53f650c EFLAGS: 00000206 ORIG_RAX: 0000000000000159 RAX: ffffffffffffffda RBX: 0000000000000008 RCX: 0000000080007fc0 RDX: 000000000800001d RSI: 000000000000001c RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 Allocated by task 4205: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 poison_kmalloc_redzone mm/kasan/common.c:398 [inline] __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415 kasan_kmalloc include/linux/kasan.h:263 [inline] __kmalloc_cache_noprof+0x31c/0x660 mm/slub.c:5297 kmalloc_noprof include/linux/slab.h:962 [inline] kzalloc_noprof include/linux/slab.h:1204 [inline] ____ip_mc_inc_group+0x518/0xdd0 net/ipv4/igmp.c:1535 __ip_mc_join_group+0x430/0x500 net/ipv4/igmp.c:2305 do_ip_setsockopt+0x2097/0x2ea0 net/ipv4/ip_sockglue.c:1310 ip_setsockopt+0x66/0x110 net/ipv4/ip_sockglue.c:1417 do_sock_setsockopt+0x17c/0x1b0 net/socket.c:2322 __sys_setsockopt net/socket.c:2347 [inline] __do_sys_setsockopt net/socket.c:2353 [inline] __se_sys_setsockopt net/socket.c:2350 [inline] __ia32_sys_setsockopt+0x13d/0x1b0 net/socket.c:2350 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline] __do_fast_syscall_32+0x20d/0x640 arch/x86/entry/syscall_32.c:307 do_fast_syscall_32+0x33/0x70 arch/x86/entry/syscall_32.c:332 entry_SYSENTER_compat_after_hwframe+0x84/0x8e Freed by task 4204: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:253 [inline] __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:2670 [inline] __rcu_free_sheaf_prepare+0x129/0x290 mm/slub.c:2900 rcu_free_sheaf+0x31/0x200 mm/slub.c:5728 rcu_do_batch kernel/rcu/tree.c:2617 [inline] rcu_core+0x7cd/0x1070 kernel/rcu/tree.c:2869 handle_softirqs+0x22a/0x870 kernel/softirq.c:622 __do_softirq kernel/softirq.c:656 [inline] invoke_softirq kernel/softirq.c:496 [inline] __irq_exit_rcu+0x5f/0x150 kernel/softirq.c:723 irq_exit_rcu+0x9/0x30 kernel/softirq.c:739 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline] sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1056 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 The buggy address belongs to the object at ffff888079159800 which belongs to the cache kmalloc-256 of size 256 The buggy address is located 8 bytes inside of freed 256-byte region [ffff888079159800, ffff888079159900) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x79158 head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff) page_type: f5(slab) raw: 00fff00000000040 ffff88813fea3b40 dead000000000100 dead000000000122 raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000 head: 00fff00000000040 ffff88813fea3b40 dead000000000100 dead000000000122 head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000 head: 00fff00000000001 ffffea0001e45601 00000000ffffffff 00000000ffffffff head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 1, migratetype Unmovable, gfp_mask 0x52820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 8789, tgid 8784 (syz.2.1186), ts 211902961285, free_ts 152700519031 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0x231/0x280 mm/page_alloc.c:1888 prep_new_page mm/page_alloc.c:1896 [inline] get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3961 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5249 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2485 alloc_slab_page mm/slub.c:3236 [inline] allocate_slab+0x83/0x660 mm/slub.c:3411 new_slab mm/slub.c:3469 [inline] ___slab_alloc+0x150/0x6a0 mm/slub.c:4334 __slab_alloc_node mm/slub.c:4400 [inline] slab_alloc_node mm/slub.c:4776 [inline] __do_kmalloc_node mm/slub.c:5176 [inline] __kmalloc_noprof+0x18a/0x760 mm/slub.c:5189 kmalloc_noprof include/linux/slab.h:966 [inline] kzalloc_noprof include/linux/slab.h:1204 [inline] hash_ipportip6_add+0x1a6f/0x23c0 net/netfilter/ipset/ip_set_hash_gen.h:950 hash_ipportip6_uadt+0x76f/0xa30 net/netfilter/ipset/ip_set_hash_ipportip.c:346 call_ad+0x398/0xb60 net/netfilter/ipset/ip_set_core.c:1751 ip_set_ad+0x824/0x9d0 net/netfilter/ipset/ip_set_core.c:1841 nfnetlink_rcv_msg+0xc00/0x12c0 net/netfilter/nfnetlink.c:302 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550 nfnetlink_rcv+0x2c0/0x27b0 net/netfilter/nfnetlink.c:669 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894 page last free pid 5845 tgid 5845 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] __free_pages_prepare mm/page_alloc.c:1432 [inline] __free_frozen_pages+0xc00/0xd90 mm/page_alloc.c:2977 __slab_free+0x263/0x2b0 mm/slub.c:5490 qlink_free mm/kasan/quarantine.c:163 [inline] qlist_free_all+0x97/0x100 mm/kasan/quarantine.c:179 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350 kasan_slab_alloc include/linux/kasan.h:253 [inline] slab_post_alloc_hook mm/slub.c:4459 [inline] slab_alloc_node mm/slub.c:4788 [inline] __kmalloc_cache_node_noprof+0x391/0x6b0 mm/slub.c:5305 kmalloc_node_noprof include/linux/slab.h:1093 [inline] __get_vm_area_node+0x13f/0x300 mm/vmalloc.c:3221 __vmalloc_node_range_noprof+0x372/0x1730 mm/vmalloc.c:4024 __vmalloc_node_noprof mm/vmalloc.c:4124 [inline] vmalloc_noprof+0xb2/0xe0 mm/vmalloc.c:4159 xt_compat_init_offsets+0xd3/0x1c0 net/netfilter/x_tables.c:733 compat_table_info+0x99/0xa80 net/ipv4/netfilter/ip_tables.c:934 get_info net/ipv4/netfilter/ip_tables.c:971 [inline] do_ipt_get_ctl+0x80d/0x1240 net/ipv4/netfilter/ip_tables.c:1659 nf_getsockopt+0x26e/0x290 net/netfilter/nf_sockopt.c:116 ip_getsockopt+0x19e/0x230 net/ipv4/ip_sockglue.c:1777 do_sock_getsockopt+0x2d3/0x3f0 net/socket.c:2383 __sys_getsockopt+0x127/0x1c0 net/socket.c:2412 Memory state around the buggy address: ffff888079159700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888079159780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff888079159800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888079159880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888079159900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== ---------------- Code disassembly (best guess): 0: 90 nop 1: 85 d2 test %edx,%edx 3: 74 0a je 0xf 5: 89 ce mov %ecx,%esi 7: 81 e6 ff 0f 00 00 and $0xfff,%esi d: 89 32 mov %esi,(%rdx) f: 85 c0 test %eax,%eax 11: 74 05 je 0x18 13: c1 e9 0c shr $0xc,%ecx 16: 89 08 mov %ecx,(%rax) 18: 31 c0 xor %eax,%eax 1a: 5e pop %rsi 1b: 5d pop %rbp 1c: c3 ret 1d: 90 nop 1e: 0f 1f 00 nopl (%rax) 21: 51 push %rcx 22: 52 push %rdx 23: 55 push %rbp 24: 89 e5 mov %esp,%ebp 26: 0f 34 sysenter 28: cd 80 int $0x80 * 2a: 5d pop %rbp <-- trapping instruction 2b: 5a pop %rdx 2c: 59 pop %rcx 2d: c3 ret 2e: 58 pop %rax 2f: b8 77 00 00 00 mov $0x77,%eax 34: cd 80 int $0x80 36: 0f 0b ud2 38: 90 nop 39: 90 nop 3a: 90 nop 3b: 90 nop 3c: 90 nop 3d: 90 nop 3e: b8 .byte 0xb8 3f: ad lods %ds:(%rsi),%eax