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From: Daeho Jeong <daeho43@gmail.com>
Date: Tue, 16 Jan 2024 13:58:18 -0800
Message-ID: <CACOAw_yL7fLmjLkK29yEb3hgTqoDO2hntOX5LMHmWjZWWix1ig@mail.gmail.com>
Subject: Re: [f2fs-dev] [PATCH v1] f2fs: fix NULL pointer dereference in f2fs_submit_page_write()
To: Wenjie Qi <qwjhust@gmail.com>
Cc: jaegeuk@kernel.org, chao@kernel.org, 
	linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, 
	hustqwj@hust.edu.cn
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On Tue, Jan 16, 2024 at 6:13=E2=80=AFAM Wenjie Qi <qwjhust@gmail.com> wrote=
:
>
> BUG: kernel NULL pointer dereference, address: 0000000000000014
> RIP: 0010:f2fs_submit_page_write+0x6cf/0x780 [f2fs]
> Call Trace:
> <TASK>
> ? show_regs+0x6e/0x80
> ? __die+0x29/0x70
> ? page_fault_oops+0x154/0x4a0
> ? prb_read_valid+0x20/0x30
> ? __irq_work_queue_local+0x39/0xd0
> ? irq_work_queue+0x36/0x70
> ? do_user_addr_fault+0x314/0x6c0
> ? exc_page_fault+0x7d/0x190
> ? asm_exc_page_fault+0x2b/0x30
> ? f2fs_submit_page_write+0x6cf/0x780 [f2fs]
> ? f2fs_submit_page_write+0x736/0x780 [f2fs]
> do_write_page+0x50/0x170 [f2fs]
> f2fs_outplace_write_data+0x61/0xb0 [f2fs]
> f2fs_do_write_data_page+0x3f8/0x660 [f2fs]
> f2fs_write_single_data_page+0x5bb/0x7a0 [f2fs]
> f2fs_write_cache_pages+0x3da/0xbe0 [f2fs]
> ...
> It is possible that other threads have added this fio to io->bio
> and submitted the io->bio before entering f2fs_submit_page_write().
> At this point io->bio =3D NULL.
> If is_end_zone_blkaddr(sbi, fio->new_blkaddr) of this fio is true,
> then an NULL pointer dereference error occurs at bio_get(io->bio).
> The original code for determining zone end was after "out:",
> which would have missed some fio who is zone end. I've moved
>  this code before "skip:" to make sure it's done for each fio.
>
> Signed-off-by: Wenjie Qi <qwjhust@gmail.com>
> ---
>  fs/f2fs/data.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index dce8defdf4c7..4f445906db8b 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1080,10 +1080,6 @@ void f2fs_submit_page_write(struct f2fs_io_info *f=
io)
>         io->last_block_in_bio =3D fio->new_blkaddr;
>
>         trace_f2fs_submit_page_write(fio->page, fio);
> -skip:
> -       if (fio->in_list)
> -               goto next;
> -out:
>  #ifdef CONFIG_BLK_DEV_ZONED
>         if (f2fs_sb_has_blkzoned(sbi) && btype < META &&
>                         is_end_zone_blkaddr(sbi, fio->new_blkaddr)) {
> @@ -1096,6 +1092,10 @@ void f2fs_submit_page_write(struct f2fs_io_info *f=
io)
>                 __submit_merged_bio(io);
>         }
>  #endif
> +skip:
> +       if (fio->in_list)
> +               goto next;
> +out:

How about moving only the "out" label instead of the whole block from
"skip" to "out"?

>         if (is_sbi_flag_set(sbi, SBI_IS_SHUTDOWN) ||
>                                 !f2fs_is_checkpoint_ready(sbi))
>                 __submit_merged_bio(io);
> --
> 2.34.1
>
>
>
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