Re: [f2fs-dev] [PATCH v1] f2fs: fix NULL pointer dereference in f2fs_submit_page_write()

[Yongpeng Yang]

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 
“bio_get(io->bio)”. 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 = 1, that fio is missed without being judged.
>
> On Wed, Jan 17, 2024 at 5:58 AM Daeho Jeong <daeho43@xxxxxxxxx> wrote:
> > On Tue, Jan 16, 2024 at 6:13 AM Wenjie Qi <qwjhust@xxxxxxxxx> 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 = 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@xxxxxxxxx>
> > > ---
> > >   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 *fio)
> > >          io->last_block_in_bio = 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 *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@xxxxxxxxxxxxxxxxxxxxx
> > > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>
>
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