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:
<TASK>
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
</TASK>
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