F2FS-fs (loop0): Magic Mismatch, valid(0xf2f52010) - read(0x0)
F2FS-fs (loop0): Can't find valid F2FS filesystem in 1th superblock
F2FS-fs (loop0): invalid crc value
==================================================================
BUG: KASAN: use-after-free in build_sit_entries fs/f2fs/segment.c:3654 [inline]
BUG: KASAN: use-after-free in build_segment_manager+0x962a/0x9d30 fs/f2fs/segment.c:3853
Read of size 4 at addr ffff8801b9ccaa00 by task syzkaller040100/3802

CPU: 0 PID: 3802 Comm: syzkaller040100 Not tainted 4.9.95-g13cc540 #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801bd2c7870 ffffffff81eb0ba9 ffffea0006e73280 ffff8801b9ccaa00
 0000000000000000 ffff8801b9ccaa00 ffff8801b5b4a200 ffff8801bd2c78a8
 ffffffff815653cb ffff8801b9ccaa00 0000000000000004 0000000000000000
Call Trace:
 [<ffffffff81eb0ba9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb0ba9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff815653cb>] print_address_description+0x6c/0x234 mm/kasan/report.c:256
 [<ffffffff815657d5>] kasan_report_error mm/kasan/report.c:355 [inline]
 [<ffffffff815657d5>] kasan_report.cold.6+0x242/0x2fe mm/kasan/report.c:412
 [<ffffffff81539434>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
 [<ffffffff81c9100a>] build_sit_entries fs/f2fs/segment.c:3654 [inline]
 [<ffffffff81c9100a>] build_segment_manager+0x962a/0x9d30 fs/f2fs/segment.c:3853
 [<ffffffff81bfe8e0>] f2fs_fill_super+0x1d10/0x5d00 fs/f2fs/super.c:2807
 [<ffffffff81579d17>] mount_bdev+0x2c7/0x390 fs/super.c:1100
 [<ffffffff81beaa94>] f2fs_mount+0x34/0x40 fs/f2fs/super.c:3024
 [<ffffffff8157ba9c>] mount_fs+0x28c/0x370 fs/super.c:1206
 [<ffffffff815db041>] vfs_kern_mount.part.29+0xd1/0x3d0 fs/namespace.c:991
 [<ffffffff815e2969>] vfs_kern_mount fs/namespace.c:973 [inline]
 [<ffffffff815e2969>] do_new_mount fs/namespace.c:2512 [inline]
 [<ffffffff815e2969>] do_mount+0x3c9/0x2740 fs/namespace.c:2834
 [<ffffffff815e56be>] SYSC_mount fs/namespace.c:3050 [inline]
 [<ffffffff815e56be>] SyS_mount+0xfe/0x110 fs/namespace.c:3027
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f2313>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

The buggy address belongs to the page:
page:ffffea0006e73280 count:0 mapcount:0 mapping:          (null) index:0x1
flags: 0x8000000000000000()
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801b9cca900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8801b9cca980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8801b9ccaa00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff8801b9ccaa80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8801b9ccab00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================