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BUG: KASAN: slab-out-of-bounds in vsscanf+0x2666/0x2ef0 lib/vsprintf.c:3321
Read of size 1 at addr ffff8880a6423ad7 by task syz-executor.5/16839

CPU: 0 PID: 16839 Comm: syz-executor.5 Not tainted 5.8.0-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+0x1f0/0x31e 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+0x2dd/0xc50 fs/read_write.c:576
 ksys_write+0x11b/0x220 fs/read_write.c:631
 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45cce9
Code: 2d 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 fb b5 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f81a7083c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000038600 RCX: 000000000045cce9
RDX: 00000000000000d6 RSI: 00000000200000c0 RDI: 0000000000000004
RBP: 000000000078bf40 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078bf0c
R13: 00007ffdf5560e5f R14: 00007f81a70849c0 R15: 000000000078bf0c

Allocated by task 16839:
 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+0x2dd/0xc50 fs/read_write.c:576
 ksys_write+0x11b/0x220 fs/read_write.c:631
 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 16230:
 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:300 [inline]
 smack_d_instantiate+0x934/0xce0 security/smack/smack_lsm.c:3431
 security_d_instantiate+0xa5/0x100 security/security.c:1957
 d_instantiate_new+0x61/0x110 fs/dcache.c:1992
 ext4_add_nondir+0x20a/0x270 fs/ext4/namei.c:2584
 ext4_symlink+0x8ba/0xef0 fs/ext4/namei.c:3372
 vfs_symlink+0x36f/0x520 fs/namei.c:3953
 do_symlinkat+0x18b/0x420 fs/namei.c:3980
 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff8880a6423a00
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 215 bytes inside of
 256-byte region [ffff8880a6423a00, ffff8880a6423b00)
The buggy address belongs to the page:
page:ffffea00029908c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea000285af88 ffffea00022255c8 ffff8880aa4008c0
raw: 0000000000000000 ffff8880a6423000 0000000100000008 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a6423980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a6423a00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880a6423a80: 00 00 00 00 00 00 00 00 00 00 07 fc fc fc fc fc
                                                 ^
 ffff8880a6423b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a6423b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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