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BUG: KASAN: slab-out-of-bounds in vsscanf+0x2666/0x2ef0 lib/vsprintf.c:3275
Read of size 1 at addr ffff88809547b502 by task syz-executor.0/4821

CPU: 0 PID: 4821 Comm: syz-executor.0 Not tainted 5.6.0-rc7-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+0x14b/0x1c0 mm/kasan/report.c:506
 kasan_report+0x25/0x50 mm/kasan/common.c:641
 vsscanf+0x2666/0x2ef0 lib/vsprintf.c:3275
 sscanf+0x6c/0x90 lib/vsprintf.c:3481
 smk_set_cipso+0x1ac/0x6a0 security/smack/smackfs.c:881
 __vfs_write+0xa7/0x710 fs/read_write.c:494
 vfs_write+0x271/0x570 fs/read_write.c:558
 ksys_write+0x115/0x220 fs/read_write.c:611
 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c849
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fb5dfd66c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fb5dfd676d4 RCX: 000000000045c849
RDX: 0000000000000001 RSI: 00000000200005c0 RDI: 0000000000000003
RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000c79 R14: 00000000004cea01 R15: 000000000076bf0c

Allocated by task 4821:
 save_stack mm/kasan/common.c:72 [inline]
 set_track mm/kasan/common.c:80 [inline]
 __kasan_kmalloc+0x118/0x1c0 mm/kasan/common.c:515
 __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
 vfs_write+0x271/0x570 fs/read_write.c:558
 ksys_write+0x115/0x220 fs/read_write.c:611
 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 4515:
 save_stack mm/kasan/common.c:72 [inline]
 set_track mm/kasan/common.c:80 [inline]
 kasan_set_free_info mm/kasan/common.c:337 [inline]
 __kasan_slab_free+0x12e/0x1e0 mm/kasan/common.c:476
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x10a/0x220 mm/slab.c:3757
 security_sk_free+0x4d/0x90 security/security.c:2106
 sk_prot_free net/core/sock.c:1636 [inline]
 __sk_destruct+0x5f9/0x740 net/core/sock.c:1724
 sock_put include/net/sock.h:1744 [inline]
 sctp_close+0x698/0x770 net/sctp/socket.c:1541
 inet_release+0x135/0x180 net/ipv4/af_inet.c:427
 __sock_release net/socket.c:605 [inline]
 sock_close+0xd8/0x260 net/socket.c:1283
 __fput+0x2d8/0x730 fs/file_table.c:280
 task_work_run+0x176/0x1b0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop arch/x86/entry/common.c:164 [inline]
 prepare_exit_to_usermode+0x48e/0x600 arch/x86/entry/common.c:195
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88809547b500
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 2 bytes inside of
 32-byte region [ffff88809547b500, ffff88809547b520)
The buggy address belongs to the page:
page:ffffea0002551ec0 refcount:1 mapcount:0 mapping:ffff8880aa4001c0 index:0xffff88809547bfc1
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea000253ce88 ffffea000278d4c8 ffff8880aa4001c0
raw: ffff88809547bfc1 ffff88809547b000 000000010000003f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88809547b400: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
 ffff88809547b480: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
>ffff88809547b500: 02 fc fc fc fc fc fc fc fb fb fb fb fc fc fc fc
                   ^
 ffff88809547b580: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
 ffff88809547b600: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
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