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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    1621b6eaebf7 Merge branch 'for-next/fixes' into for-kernelci
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=12ed633e880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=606e57fd25c5c6cc
dashboard link: https://syzkaller.appspot.com/bug?extid=5afc832d6dbb2fd17538
compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: arm64

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/82aa7741098d/disk-1621b6ea.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f6be08c4e4c2/vmlinux-1621b6ea.xz
kernel image: https://storage.googleapis.com/syzbot-assets/296b6946258a/Image-1621b6ea.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5afc832d6dbb2fd17538@xxxxxxxxxxxxxxxxxxxxxxxxx

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
Mem abort info:
  ESR = 0x0000000086000006
  EC = 0x21: IABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x06: level 2 translation fault
user pgtable: 4k pages, 48-bit VAs, pgdp=000000015174f000
[0000000000000000] pgd=080000015c4bd003, p4d=080000015c4bd003, pud=080000015c4c1003, pmd=0000000000000000
Internal error: Oops: 0000000086000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 12611 Comm: syz-executor.4 Not tainted 6.1.0-rc4-syzkaller-31872-g1621b6eaebf7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/30/2022
pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : 0x0
lr : nilfs_segctor_update_payload_blocknr+0x27c/0x3c8
sp : ffff800014093840
x29: ffff8000140938a0 x28: ffff000110709128 x27: 0000000000000000
x26: ffff0000ca340a80 x25: 0000000000000000 x24: 0000000000000000
x23: 0000000000000106 x22: ffff0000ca37ec38 x21: ffff000117008440
x20: ffff0000ca340ac8 x19: 0000000000000106 x18: 00000000000000c0
x17: ffff80000dcdc198 x16: ffff80000db1a158 x15: ffff000128253480
x14: 0000000000000000 x13: 00000000ffffffff x12: ffff000128253480
x11: ff80800008f8ace0 x10: 0000000000000000 x9 : ffff80000c188130
x8 : 0000000000000000 x7 : ffff8000095f3074 x6 : 0000000000000000
x5 : ffff000128253480 x4 : fffffbffeffe5720 x3 : 0000000000002491
x2 : ffff800014093878 x1 : ffff800014093888 x0 : ffff000110d6f000
Call trace:
 0x0
 nilfs_segctor_assign fs/nilfs2/segment.c:1629 [inline]
 nilfs_segctor_do_construct+0x750/0xefc fs/nilfs2/segment.c:2056
 nilfs_construct_dsync_segment+0x21c/0x2ec fs/nilfs2/segment.c:2310
 nilfs_writepages+0x6c/0xa8 fs/nilfs2/inode.c:170
 do_writepages+0x144/0x27c mm/page-writeback.c:2469
 filemap_fdatawrite_wbc+0xac/0xd0 mm/filemap.c:388
 __filemap_fdatawrite_range mm/filemap.c:421 [inline]
 filemap_write_and_wait_range+0x84/0x1e8 mm/filemap.c:674
 __generic_file_write_iter+0x188/0x21c mm/filemap.c:3867
 generic_file_write_iter+0x6c/0x168 mm/filemap.c:3913
 call_write_iter include/linux/fs.h:2191 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x2dc/0x46c fs/read_write.c:584
 ksys_write+0xb4/0x160 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __arm64_sys_write+0x24/0x34 fs/read_write.c:646
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
 el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x48/0x164 arch/arm64/kernel/syscall.c:206
 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:584
Code: bad PC value
---[ end trace 0000000000000000 ]---


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