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BUG: KASAN: slab-out-of-bounds in vsscanf+0x2666/0x2ef0 lib/vsprintf.c:3321
Read of size 1 at addr ffff8880985444d7 by task syz-executor.4/8948

CPU: 0 PID: 8948 Comm: syz-executor.4 Not tainted 5.7.0-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+0x66/0x5a0 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report+0x132/0x1d0 mm/kasan/report.c:530
 vsscanf+0x2666/0x2ef0 lib/vsprintf.c:3321
 sscanf+0x6c/0x90 lib/vsprintf.c:3527
 smk_set_cipso+0x374/0x6c0 security/smack/smackfs.c:908
 __vfs_write+0x9c/0x6e0 fs/read_write.c:495
 vfs_write+0x274/0x580 fs/read_write.c:559
 ksys_write+0x11b/0x220 fs/read_write.c:612
 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x45ca59
Code: 0d b7 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 db b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fcc02afcc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000050dba0 RCX: 000000000045ca59
RDX: 00000000000000d6 RSI: 0000000020000080 RDI: 0000000000000003
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000d27 R14: 00000000004cf7f2 R15: 00007fcc02afd6d4

Allocated by task 8948:
 save_stack mm/kasan/common.c:48 [inline]
 set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc+0x103/0x140 mm/kasan/common.c:494
 __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/0x6c0 security/smack/smackfs.c:859
 __vfs_write+0x9c/0x6e0 fs/read_write.c:495
 vfs_write+0x274/0x580 fs/read_write.c:559
 ksys_write+0x11b/0x220 fs/read_write.c:612
 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3

Freed by task 3875:
 save_stack mm/kasan/common.c:48 [inline]
 set_track mm/kasan/common.c:56 [inline]
 kasan_set_free_info mm/kasan/common.c:316 [inline]
 __kasan_slab_free+0x114/0x170 mm/kasan/common.c:455
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x10a/0x220 mm/slab.c:3757
 smk_fetch security/smack/smack_lsm.c:299 [inline]
 smack_d_instantiate+0xa93/0xce0 security/smack/smack_lsm.c:3436
 security_d_instantiate+0xa5/0x100 security/security.c:1930
 d_splice_alias+0x71/0x5f0 fs/dcache.c:3029
 kernfs_iop_lookup+0x1e5/0x290 fs/kernfs/dir.c:1108
 __lookup_slow+0x240/0x370 fs/namei.c:1530
 lookup_slow fs/namei.c:1547 [inline]
 walk_component+0x442/0x680 fs/namei.c:1846
 lookup_last fs/namei.c:2295 [inline]
 path_lookupat+0x19d/0x960 fs/namei.c:2319
 filename_lookup+0x1ab/0x5d0 fs/namei.c:2352
 do_readlinkat+0xb7/0x330 fs/stat.c:419
 __do_sys_readlinkat fs/stat.c:446 [inline]
 __se_sys_readlinkat fs/stat.c:443 [inline]
 __x64_sys_readlinkat+0x96/0xb0 fs/stat.c:443
 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3

The buggy address belongs to the object at ffff888098544400
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 215 bytes inside of
 256-byte region [ffff888098544400, ffff888098544500)
The buggy address belongs to the page:
page:ffffea0002615100 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002618ac8 ffffea000239c188 ffff8880aa4008c0
raw: 0000000000000000 ffff888098544000 0000000100000008 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888098544380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888098544400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888098544480: 00 00 00 00 00 00 00 00 00 00 07 fc fc fc fc fc
                                                 ^
 ffff888098544500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888098544580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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