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BUG: KASAN: slab-out-of-bounds in vsscanf+0x2666/0x2ef0 lib/vsprintf.c:3275
Read of size 1 at addr ffff8880a1edeb82 by task syz-executor.1/15447

CPU: 0 PID: 15447 Comm: syz-executor.1 Not tainted 5.6.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1e9/0x30e lib/dump_stack.c:118
 print_address_description+0x74/0x5c0 mm/kasan/report.c:374
 __kasan_report+0x103/0x190 mm/kasan/report.c:503
 kasan_report+0x4d/0x80 mm/kasan/common.c:648

Allocated by task 15447:
 save_stack mm/kasan/common.c:72 [inline]
 set_track mm/kasan/common.c:80 [inline]
 __kasan_kmalloc+0x118/0x1c0 mm/kasan/common.c:518
 __do_kmalloc mm/slab.c:3656 [inline]
 __kmalloc_track_caller+0x249/0x320 mm/slab.c:3671
 memdup_user_nul+0x26/0xf0 mm/util.c:259
 smk_set_cipso+0xff/0x6a0 security/smack/smackfs.c:859
 __vfs_write+0xa7/0x710 fs/read_write.c:494
 __kernel_write+0x120/0x350 fs/read_write.c:515
 write_pipe_buf+0xf9/0x150 fs/splice.c:809
 splice_from_pipe_feed fs/splice.c:512 [inline]
 __splice_from_pipe+0x329/0x870 fs/splice.c:636
 splice_from_pipe fs/splice.c:671 [inline]
 default_file_splice_write+0x112/0x1b0 fs/splice.c:821
 do_splice_from fs/splice.c:863 [inline]
 do_splice+0xdcd/0x18c0 fs/splice.c:1170
 __do_sys_splice fs/splice.c:1447 [inline]
 __se_sys_splice+0x172/0x230 fs/splice.c:1427
 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3

Freed by task 21:
 save_stack mm/kasan/common.c:72 [inline]
 set_track mm/kasan/common.c:80 [inline]
 kasan_set_free_info mm/kasan/common.c:340 [inline]
 __kasan_slab_free+0x12e/0x1e0 mm/kasan/common.c:479
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x10a/0x220 mm/slab.c:3757
 batadv_mcast_mla_list_free net/batman-adv/multicast.c:671 [inline]
 __batadv_mcast_mla_update net/batman-adv/multicast.c:926 [inline]
 batadv_mcast_mla_update+0x3374/0x3820 net/batman-adv/multicast.c:948
 process_one_work+0x76e/0xfd0 kernel/workqueue.c:2266
 worker_thread+0xa7f/0x1450 kernel/workqueue.c:2412
 kthread+0x353/0x380 kernel/kthread.c:268
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff8880a1edeb80
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 2 bytes inside of
 32-byte region [ffff8880a1edeb80, ffff8880a1edeba0)
The buggy address belongs to the page:
page:ffffea000287b780 refcount:1 mapcount:0 mapping:00000000ad50185b index:0xffff8880a1edefc1
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002764048 ffffea0002937ac8 ffff8880aa4001c0
raw: ffff8880a1edefc1 ffff8880a1ede000 000000010000003f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a1edea80: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
 ffff8880a1edeb00: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
>ffff8880a1edeb80: 02 fc fc fc fc fc fc fc fb fb fb fb fc fc fc fc
                   ^
 ffff8880a1edec00: 02 fc fc fc fc fc fc fc fb fb fb fb fc fc fc fc
 ffff8880a1edec80: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
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