[syzbot] [erofs?] [mm?] BUG: unable to handle kernel NULL pointer dereference in filemap_read_folio (3)

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+001306cd9c92ce0df23f at syzkaller.appspotmail.com
Tested-by: syzbot+001306cd9c92ce0df23f at syzkaller.appspotmail.com

Tested on:

commit:         2830df2e erofs: ensure regular inodes for file-backed ..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git dev-test
console output: https://syzkaller.appspot.com/x/log.txt?x=11b168a9980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a43f85ec3262ab75
dashboard link: https://syzkaller.appspot.com/bug?extid=001306cd9c92ce0df23f
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.