Syzkaller hit 'memory leak in ext4_multi_mount_protect - Fixed' bug.

BUG: memory leak
unreferenced object 0xffff88800f2dfbc0 (size 16):
  comm "syz-executor.2", pid 4201, jiffies 4295870614 (age 13.468s)
  hex dump (first 16 bytes):
    c8 cb 2c 19 80 88 ff ff 00 40 a0 15 80 88 ff ff  ..,......@......
  backtrace:
    [<0000000005565a3b>] kmalloc include/linux/slab.h:552 [inline]
    [<0000000005565a3b>] ext4_multi_mount_protect+0x861/0xb20 fs/ext4/mmp.c:367
    [<00000000f466d1f0>] ext4_fill_super+0xa20e/0xcf20 fs/ext4/super.c:4774
    [<00000000bb77c9a4>] mount_bdev+0x331/0x3f0 fs/super.c:1419
    [<0000000098cfbb69>] legacy_get_tree+0x105/0x220 fs/fs_context.c:592
    [<00000000887a730b>] vfs_get_tree+0x8e/0x2f0 fs/super.c:1549
    [<00000000e1e3e4bc>] do_new_mount fs/namespace.c:2881 [inline]
    [<00000000e1e3e4bc>] path_mount+0x139a/0x2080 fs/namespace.c:3211
    [<00000000a572740b>] do_mount fs/namespace.c:3224 [inline]
    [<00000000a572740b>] __do_sys_mount fs/namespace.c:3432 [inline]
    [<00000000a572740b>] __se_sys_mount fs/namespace.c:3409 [inline]
    [<00000000a572740b>] __x64_sys_mount+0x27e/0x300 fs/namespace.c:3409
    [<00000000070ce5e4>] do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46
    [<000000003bd3a3c1>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

BUG: memory leak
unreferenced object 0xffff88800f2dfa20 (size 16):
  comm "syz-executor.5", pid 4199, jiffies 4295870615 (age 13.467s)
  hex dump (first 16 bytes):
    98 cd 2c 19 80 88 ff ff 00 00 ac 15 80 88 ff ff  ..,.............
  backtrace:
    [<0000000005565a3b>] kmalloc include/linux/slab.h:552 [inline]
    [<0000000005565a3b>] ext4_multi_mount_protect+0x861/0xb20 fs/ext4/mmp.c:367
    [<00000000f466d1f0>] ext4_fill_super+0xa20e/0xcf20 fs/ext4/super.c:4774
    [<00000000bb77c9a4>] mount_bdev+0x331/0x3f0 fs/super.c:1419
    [<0000000098cfbb69>] legacy_get_tree+0x105/0x220 fs/fs_context.c:592
    [<00000000887a730b>] vfs_get_tree+0x8e/0x2f0 fs/super.c:1549
    [<00000000e1e3e4bc>] do_new_mount fs/namespace.c:2881 [inline]
    [<00000000e1e3e4bc>] path_mount+0x139a/0x2080 fs/namespace.c:3211
    [<00000000a572740b>] do_mount fs/namespace.c:3224 [inline]
    [<00000000a572740b>] __do_sys_mount fs/namespace.c:3432 [inline]
    [<00000000a572740b>] __se_sys_mount fs/namespace.c:3409 [inline]
    [<00000000a572740b>] __x64_sys_mount+0x27e/0x300 fs/namespace.c:3409
    [<00000000070ce5e4>] do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46
    [<000000003bd3a3c1>] entry_SYSCALL_64_after_hwframe+0x44/0xa9



Syzkaller reproducer:
# {Threaded:false Collide:false Repeat:true RepeatTimes:0 Procs:8 Slowdown:1 Sandbox:none Fault:false FaultCall:-1 FaultNth:0 Leak:true NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false USB:true VhciInjection:false Wifi:false IEEE802154:false Sysctl:true UseTmpDir:true HandleSegv:true Repro:false Trace:false}
syz_mount_image$ext4(&(0x7f0000000000)='ext4\x00', &(0x7f0000000100)='./file0\x00', 0x40013, 0x21, &(0x7f0000000200)=[{&(0x7f0000010000)="200000008000000006000000600000000f000000000000000100000001000000004000000040000020000000d2f4655fd2f4655f0100ffff53ef010001000000d0f4655f000000000000000001000000000000000b000000800000000800000052470000620100000000000000000000000000000000000073797a6b616c6c6572000000000000002f746d702f73797a2d696d61676567656e38333031383839323800"/192, 0xc0, 0x400}, {0x0, 0x0, 0x4e0}, {&(0x7f0000010200)="01000000000005000c0000000000000000000000040000004b00000000000000", 0x20, 0x560}, {0x0, 0x0, 0x640}, {&(0x7f0000010400)="02000000120000002200000060000f0003000400"/32, 0x20, 0x800}, {0x0, 0x0, 0x1000}, {0x0, 0x0, 0x2000}, {0x0, 0x0, 0x2800}, {0x0, 0x0, 0x3000}, {0x0, 0x0, 0x3800}, {0x0, 0x0, 0x4000}, {0x0, 0x0, 0x4800}, {0x0, 0x0, 0x5000}, {0x0, 0x0, 0x5800}, {&(0x7f0000011600)="504d4d00504d4dffd2f4655f00000000647679756b6f762d676c6170746f70320000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000006c6f6f7033320075782f746573742f73797a5f6d6f756e745f696d6167655f650500"/128, 0x80, 0x6000}, {0x0, 0x0, 0x6800}, {0x0, 0x0, 0x6c00}, {0x0, 0x0, 0x7000}, {0x0, 0x0, 0x7400}, {0x0, 0x0, 0x7800}, {0x0, 0x0, 0x7c00}, {0x0, 0x0, 0x8000}, {0x0, 0x0, 0x8400}, {0x0, 0x0, 0x8800}, {0x0, 0x0, 0x8c00}, {0x0, 0x0, 0x9000}, {0x0, 0x0, 0x9c00}, {0x0, 0x0, 0x10000}, {0x0, 0x0, 0x10800}, {0x0, 0x0, 0x10fe0}, {0x0, 0x0, 0x11080}, {0x0, 0x0, 0x11100}, {0x0, 0x0, 0x11180}], 0x0, &(0x7f0000013c00))