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BUG: KASAN: slab-out-of-bounds in vsscanf+0x2666/0x2ef0 lib/vsprintf.c:3275
Read of size 1 at addr ffff888091b215c2 by task syz-executor.0/22603

CPU: 0 PID: 22603 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:00007fd3cc4b3c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fd3cc4b46d4 RCX: 000000000045c849
RDX: 0000000000000001 RSI: 0000000020001400 RDI: 0000000000000003
RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000cfa R14: 00000000004cf202 R15: 000000000076bf0c

Allocated by task 22603:
 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 22417:
 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
 smk_import_entry+0x40f/0x560 security/smack/smack_access.c:578
 smk_fetch security/smack/smack_lsm.c:300 [inline]
 smack_d_instantiate+0x6e1/0xd90 security/smack/smack_lsm.c:3408
 security_d_instantiate+0xa5/0x100 security/security.c:1906
 d_instantiate_new+0x61/0x110 fs/dcache.c:1973
 ext4_add_nondir+0x1f6/0x260 fs/ext4/namei.c:2582
 ext4_symlink+0x8ba/0xef0 fs/ext4/namei.c:3364
 vfs_symlink+0x36f/0x500 fs/namei.c:4201
 do_symlinkat+0x18b/0x420 fs/namei.c:4228
 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff888091b215c0
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 2 bytes inside of
 32-byte region [ffff888091b215c0, ffff888091b215e0)
The buggy address belongs to the page:
page:ffffea000246c840 refcount:1 mapcount:0 mapping:ffff8880aa4001c0 index:0xffff888091b21fc1
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0000e99108 ffffea00027a6f48 ffff8880aa4001c0
raw: ffff888091b21fc1 ffff888091b21000 000000010000003c 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888091b21480: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
 ffff888091b21500: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
>ffff888091b21580: 00 fc fc fc fc fc fc fc 02 fc fc fc fc fc fc fc
                                           ^
 ffff888091b21600: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
 ffff888091b21680: 00 00 fc fc fc fc fc fc fb fb fb fb fc fc fc fc
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