memory leak in generic_parse_monolithic

[syzbot <syzbot+86dc6632faaca40133ab@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    af5043c8 Merge tag 'acpi-5.10-rc4' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13e8c906500000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a3f13716fa0212fd
dashboard link: https://syzkaller.appspot.com/bug?extid=86dc6632faaca40133ab
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=102a57dc500000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=129ca3d6500000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+86dc6632faaca40133ab@syzkaller.appspotmail.com

Warning: Permanently added '10.128.0.84' (ECDSA) to the list of known hosts.
executing program
executing program
BUG: memory leak
unreferenced object 0xffff888111f15a80 (size 32):
  comm "syz-executor841", pid 8507, jiffies 4294942125 (age 14.070s)
  hex dump (first 32 bytes):
    25 5e 5d 24 5b 2b 25 5d 28 24 7b 3a 0f 6b 5b 29  %^]$[+%](${:.k[)
    2d 3a 00 00 00 00 00 00 00 00 00 00 00 00 00 00  -:..............
  backtrace:
    [<000000005c6f565d>] kmemdup_nul+0x2d/0x70 mm/util.c:151
    [<0000000054985c27>] vfs_parse_fs_string+0x6e/0xd0 fs/fs_context.c:155
    [<0000000077ef66e4>] generic_parse_monolithic+0xe0/0x130 fs/fs_context.c:201
    [<00000000d4d4a652>] do_new_mount fs/namespace.c:2871 [inline]
    [<00000000d4d4a652>] path_mount+0xbbb/0x1170 fs/namespace.c:3205
    [<00000000f43f0071>] do_mount fs/namespace.c:3218 [inline]
    [<00000000f43f0071>] __do_sys_mount fs/namespace.c:3426 [inline]
    [<00000000f43f0071>] __se_sys_mount fs/namespace.c:3403 [inline]
    [<00000000f43f0071>] __x64_sys_mount+0x18e/0x1d0 fs/namespace.c:3403
    [<00000000dc5fffd5>] do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
    [<000000004e665669>] entry_SYSCALL_64_after_hwframe+0x44/0xa9



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