[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+07ff38...@syzkaller.appspotmail.com

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


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[Hillf Danton]

On Sun, 25 Jul 2021 23:00:19 -0700

> 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.

Given the code [1], curious about the reasons possible behind this report.

2416 void f2fs_update_meta_page(struct f2fs_sb_info *sbi,
2417 void *src, block_t blk_addr)
2418 {
2419 struct page *page = f2fs_grab_meta_page(sbi, blk_addr);
2420
2421 memcpy(page_address(page), src, PAGE_SIZE);
2422 set_page_dirty(page);
2423 f2fs_put_page(page, 1);
2424 }

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/f2fs/segment.c?id=6498f6151825#n2422

[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.