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From: Wenjie Qi <qwjhust@gmail.com>
Date: Wed, 17 Jan 2024 19:27:26 +0800
Message-ID: <CAGFpFsT6XyTNPRxrTg+=F_eQ_-cryhdYd-k7rXxy1oJn4F4oLA@mail.gmail.com>
Subject: Re: [f2fs-dev] [PATCH v1] f2fs: fix NULL pointer dereference in f2fs_submit_page_write()
To: Yongpeng Yang <yangyongpeng1@oppo.com>
Cc: jaegeuk@kernel.org, linux-kernel@vger.kernel.org, hustqwj@hust.edu.cn, 
	linux-f2fs-devel@lists.sourceforge.net, chao@kernel.org
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Hello Yongpeng,
I don't think that's correct.
If list_empty(&io->io_list) and fio->in_list are true, it will jump to
the "out" label. This does not enter the judgment process.
In addition,  __bio_alloc() will ensure that io->bio ! =3D NULL.

On Wed, Jan 17, 2024 at 6:17=E2=80=AFPM Yongpeng Yang <yangyongpeng1@oppo.c=
om> wrote:
>
> Hello Wenjie,
> This patch does not prevent the simultaneous truth of
> list_empty(&io->io_list), fio->in_list, and is_end_zone_blkaddr(sbi,
> fio->new_blkaddr). NULL pointer dereference error still exists in
> =E2=80=9Cbio_get(io->bio)=E2=80=9D. Is that correct?
>
> On 1/17/2024 9:39 AM, Wenjie Qi wrote:
> > Hello Daeho,
> > I don't think moving just the "out" label will work.
> > If a fio is zone end and in_list =3D 1, that fio is missed without bein=
g judged.
> >
> > On Wed, Jan 17, 2024 at 5:58=E2=80=AFAM Daeho Jeong <daeho43@gmail.com>=
 wrote:
> >>
> >> 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_inf=
o *fio)
> >>>          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_inf=
o *fio)
> >>>                  __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
> >>>
> >>>
> >>>
> >>> _______________________________________________
> >>> Linux-f2fs-devel mailing list
> >>> Linux-f2fs-devel@lists.sourceforge.net
> >>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
> >
> >
> > _______________________________________________
> > Linux-f2fs-devel mailing list
> > Linux-f2fs-devel@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel