[syzbot] BUG: unable to handle kernel NULL pointer dereference in f2fs_update_meta_page

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    6498f6151825 Merge tag 'riscv-for-linus-5.14-rc3' of git:/..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14bbce46300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5dc0e3202ae2f574
dashboard link: https://syzkaller.appspot.com/bug?extid=07ff38c9c93ca170de07
compiler:       Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+07ff38c9c93ca170de07@xxxxxxxxxxxxxxxxxxxxxxxxx

BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 7395a067 P4D 7395a067 PUD 7395b067 PMD 0 
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 14793 Comm: syz-executor.3 Not tainted 5.14.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc9000158f858 EFLAGS: 00010286
RAX: 1ffffffff147d97b RBX: 00000000000005ff RCX: ffffffff8a3ecbd8
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffea00027e9540
RBP: ffffc9000158fad0 R08: ffffffff81aa846c R09: fffff940004fd2a9
R10: fffff940004fd2a9 R11: 0000000000000000 R12: ffff888081491310
R13: 0000000000000001 R14: ffff88807fa0e000 R15: ffffea00027e9540
FS:  0000000002a84400(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 0000000073959000 CR4: 00000000001526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 f2fs_update_meta_page+0x4b/0x380 fs/f2fs/segment.c:2422
 do_checkpoint fs/f2fs/checkpoint.c:1492 [inline]
 f2fs_write_checkpoint+0x2f1b/0x5060 fs/f2fs/checkpoint.c:1650
 f2fs_issue_checkpoint+0x308/0x4a0 fs/f2fs/checkpoint.c:1718
 __sync_filesystem fs/sync.c:39 [inline]
 sync_filesystem+0x19e/0x200 fs/sync.c:67
 generic_shutdown_super+0x6e/0x2b0 fs/super.c:448
 kill_block_super+0x79/0xd0 fs/super.c:1395
 kill_f2fs_super+0x2f9/0x3c0 fs/f2fs/super.c:4329
 deactivate_locked_super+0xa7/0xf0 fs/super.c:335
 cleanup_mnt+0x462/0x510 fs/namespace.c:1136
 task_work_run+0x146/0x1c0 kernel/task_work.c:164
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
 exit_to_user_mode_prepare+0x201/0x220 kernel/entry/common.c:209
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x26/0x60 kernel/entry/common.c:302
 do_syscall_64+0x4c/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x467a47
Code: ff d0 48 89 c7 b8 3c 00 00 00 0f 05 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 b8 a6 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fffa4976ab8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000467a47
RDX: 00007fffa4976b8b RSI: 0000000000000002 RDI: 00007fffa4976b80
RBP: 00007fffa4976b80 R08: 00000000ffffffff R09: 00007fffa4976950
R10: 0000000002a858e3 R11: 0000000000000246 R12: 00000000004bee90
R13: 00007fffa4977c50 R14: 0000000002a85810 R15: 00007fffa4977c90
Modules linked in:
CR2: 0000000000000000
---[ end trace dff6785899946653 ]---
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc9000158f858 EFLAGS: 00010286
RAX: 1ffffffff147d97b RBX: 00000000000005ff RCX: ffffffff8a3ecbd8
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffea00027e9540
RBP: ffffc9000158fad0 R08: ffffffff81aa846c R09: fffff940004fd2a9
R10: fffff940004fd2a9 R11: 0000000000000000 R12: ffff888081491310
R13: 0000000000000001 R14: ffff88807fa0e000 R15: ffffea00027e9540
FS:  0000000002a84400(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 0000000073959000 CR4: 00000000001526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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