==================================================================
BUG: KASAN: use-after-free in ip_check_mc_rcu+0x586/0x640 net/ipv4/igmp.c:2720
Read of size 8 at addr ffff888019231250 by task syz-executor.4/10527

CPU: 1 PID: 10527 Comm: syz-executor.4 Not tainted 5.12.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x176/0x24e lib/dump_stack.c:120
 print_address_description+0x5f/0x3a0 mm/kasan/report.c:232
 __kasan_report mm/kasan/report.c:399 [inline]
 kasan_report+0x15c/0x200 mm/kasan/report.c:416
 ip_check_mc_rcu+0x586/0x640 net/ipv4/igmp.c:2720
 __mkroute_output net/ipv4/route.c:2405 [inline]
 ip_route_output_key_hash_rcu+0xf4f/0x25c0 net/ipv4/route.c:2684
 ip_route_output_key_hash+0x14a/0x260 net/ipv4/route.c:2512
 __ip_route_output_key include/net/route.h:126 [inline]
 ip_route_output_flow+0x25/0x130 net/ipv4/route.c:2744
 udp_sendmsg+0x1b8f/0x2f20 net/ipv4/udp.c:1206
 sock_sendmsg_nosec net/socket.c:654 [inline]
 sock_sendmsg net/socket.c:674 [inline]
 ____sys_sendmsg+0x519/0x800 net/socket.c:2350
 ___sys_sendmsg net/socket.c:2404 [inline]
 __sys_sendmmsg+0x453/0x680 net/socket.c:2490
 __do_sys_sendmmsg net/socket.c:2519 [inline]
 __se_sys_sendmmsg net/socket.c:2516 [inline]
 __x64_sys_sendmmsg+0x9c/0xb0 net/socket.c:2516
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x466459
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f47e3f4b188 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000466459
RDX: 000000000800001d RSI: 0000000020007fc0 RDI: 0000000000000004
RBP: 00000000004bf9fb R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60
R13: 00007ffc5ebcde0f R14: 00007f47e3f4b300 R15: 0000000000022000

Allocated by task 10527:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:427 [inline]
 ____kasan_kmalloc+0xc2/0xf0 mm/kasan/common.c:506
 kasan_kmalloc include/linux/kasan.h:233 [inline]
 kmem_cache_alloc_trace+0x21b/0x350 mm/slub.c:2934
 kmalloc include/linux/slab.h:554 [inline]
 kzalloc include/linux/slab.h:684 [inline]
 ip_mc_add1_src net/ipv4/igmp.c:1971 [inline]
 ip_mc_add_src+0x786/0xda0 net/ipv4/igmp.c:2095
 ip_mc_msfilter+0x571/0xa80 net/ipv4/igmp.c:2479
 do_ip_setsockopt net/ipv4/ip_sockglue.c:1255 [inline]
 ip_setsockopt+0x3a8e/0x4d30 net/ipv4/ip_sockglue.c:1423
 __sys_setsockopt+0x4b8/0x880 net/socket.c:2117
 __do_sys_setsockopt net/socket.c:2128 [inline]
 __se_sys_setsockopt net/socket.c:2125 [inline]
 __x64_sys_setsockopt+0xb1/0xc0 net/socket.c:2125
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 10517:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x3d/0x70 mm/kasan/common.c:46
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:357
 ____kasan_slab_free+0x100/0x140 mm/kasan/common.c:360
 kasan_slab_free include/linux/kasan.h:199 [inline]
 slab_free_hook mm/slub.c:1562 [inline]
 slab_free_freelist_hook+0x171/0x270 mm/slub.c:1600
 slab_free mm/slub.c:3161 [inline]
 kfree+0xcf/0x2d0 mm/slub.c:4213
 ip_mc_del1_src+0x6ff/0x860 net/ipv4/igmp.c:1884
 ip_mc_del_src+0x656/0xa60 net/ipv4/igmp.c:1925
 ip_mc_leave_src+0x10b/0x200 net/ipv4/igmp.c:2231
 ip_mc_drop_socket+0x1c4/0x260 net/ipv4/igmp.c:2677
 inet_release+0x82/0x1f0 net/ipv4/af_inet.c:418
 __sock_release net/socket.c:599 [inline]
 sock_close+0xd8/0x260 net/socket.c:1258
 __fput+0x352/0x7b0 fs/file_table.c:280
 task_work_run+0x146/0x1c0 kernel/task_work.c:140
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
 exit_to_user_mode_prepare+0x10b/0x1e0 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x26/0x70 kernel/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x44/0xae

The buggy address belongs to the object at ffff888019231240
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 16 bytes inside of
 32-byte region [ffff888019231240, ffff888019231260)
The buggy address belongs to the page:
page:ffffea0000648c40 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888019231a80 pfn:0x19231
flags: 0xfff00000000200(slab)
raw: 00fff00000000200 ffffea0000482a00 0000000900000009 ffff888010841500
raw: ffff888019231a80 000000008040003f 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888019231100: 00 00 00 fc fc fc fc fc fa fb fb fb fc fc fc fc
 ffff888019231180: 00 00 01 fc fc fc fc fc fa fb fb fb fc fc fc fc
>ffff888019231200: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
                                                 ^
 ffff888019231280: fa fb fb fb fc fc fc fc 00 00 01 fc fc fc fc fc
 ffff888019231300: 00 00 01 fc fc fc fc fc fa fb fb fb fc fc fc fc
==================================================================