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Date:   Thu, 25 Aug 2022 18:37:34 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     syzbot <syzbot+775a3440817f74fddb8c@syzkaller.appspotmail.com>
Cc:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, syzkaller-bugs@googlegroups.com,
        willy@infradead.org, Jaegeuk Kim <jaegeuk@kernel.org>,
        Chao Yu <chao@kernel.org>,
        linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [syzbot] BUG: unable to handle kernel NULL pointer dereference
 in set_page_dirty
Message-Id: <20220825183734.0b08ae10a2e9e1bd156a19cd@linux-foundation.org>
In-Reply-To: <000000000000d5b4fe05e7127662@google.com>
References: <000000000000d5b4fe05e7127662@google.com>
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(cc fsf2 developers)

On Thu, 25 Aug 2022 08:29:32 -0700 syzbot <syzbot+775a3440817f74fddb8c@syzkaller.appspotmail.com> wrote:

> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    a41a877bc12d 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=175def47080000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=5cea15779c42821c
> dashboard link: https://syzkaller.appspot.com/bug?extid=775a3440817f74fddb8c
> 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.
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+775a3440817f74fddb8c@syzkaller.appspotmail.com
> 
> Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
> Mem abort info:
>   ESR = 0x0000000086000005
>   EC = 0x21: IABT (current EL), IL = 32 bits
>   SET = 0, FnV = 0
>   EA = 0, S1PTW = 0
>   FSC = 0x05: level 1 translation fault
> user pgtable: 4k pages, 48-bit VAs, pgdp=00000001249cc000
> [0000000000000000] pgd=080000012ee65003, p4d=080000012ee65003, pud=0000000000000000
> Internal error: Oops: 86000005 [#1] PREEMPT SMP
> Modules linked in:
> CPU: 0 PID: 3044 Comm: syz-executor.0 Not tainted 6.0.0-rc2-syzkaller-16455-ga41a877bc12d #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/20/2022
> pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : 0x0
> lr : folio_mark_dirty+0xbc/0x208 mm/page-writeback.c:2748
> sp : ffff800012803830
> x29: ffff800012803830 x28: ffff0000d02c8000 x27: 0000000000000009
> x26: 0000000000000001 x25: 0000000000000a00 x24: 0000000000000080
> x23: 0000000000000000 x22: ffff0000ef276c00 x21: 05ffc00000000007
> x20: ffff0000f14b83b8 x19: fffffc00036409c0 x18: fffffffffffffff5
> x17: ffff80000dd7a698 x16: ffff80000dbb8658 x15: 0000000000000000
> x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
> x11: ff808000083e9814 x10: 0000000000000000 x9 : ffff8000083e9814
> x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
> x5 : ffff0000d9028000 x4 : ffff0000d5c31000 x3 : ffff0000d9027f80
> x2 : fffffffffffffff0 x1 : fffffc00036409c0 x0 : ffff0000f14b83b8
> Call trace:
>  0x0
>  set_page_dirty+0x38/0xbc mm/folio-compat.c:62
>  get_next_nat_page+0x198/0x300 fs/f2fs/node.c:154
>  __flush_nat_entry_set fs/f2fs/node.c:3005 [inline]
>  f2fs_flush_nat_entries+0x354/0x988 fs/f2fs/node.c:3109
>  f2fs_write_checkpoint+0x350/0x568 fs/f2fs/checkpoint.c:1667
>  f2fs_issue_checkpoint+0x1b0/0x234
>  f2fs_sync_fs+0x8c/0xc8 fs/f2fs/super.c:1651
>  sync_filesystem+0xe0/0x134 fs/sync.c:66
>  generic_shutdown_super+0x38/0x190 fs/super.c:474
>  kill_block_super+0x30/0x78 fs/super.c:1427
>  kill_f2fs_super+0x140/0x184 fs/f2fs/super.c:4544
>  deactivate_locked_super+0x70/0xd4 fs/super.c:332
>  deactivate_super+0xb8/0xbc fs/super.c:363
>  cleanup_mnt+0x1f8/0x234 fs/namespace.c:1186
>  __cleanup_mnt+0x20/0x30 fs/namespace.c:1193
>  task_work_run+0xc4/0x208 kernel/task_work.c:177
>  resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
>  do_notify_resume+0x174/0x1d0 arch/arm64/kernel/signal.c:1127
>  prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
>  exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
>  el0_svc+0x9c/0x150 arch/arm64/kernel/entry-common.c:625
>  el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:642
>  el0t_64_sync+0x18c/0x190
> Code: bad PC value
> ---[ end trace 0000000000000000 ]---
> 
> 
> ---
> 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 syzkaller@googlegroups.com.
> 
> syzbot will keep track of this issue. See:
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