Re: [f2fs-dev] [PATCH] f2fs: avoid null pointer access when handling IPU error

[Chao Yu]

On 2021/5/11 13:07, Jaegeuk Kim wrote:
> On 05/11, Chao Yu wrote:
> > On 2021/5/10 22:28, Jaegeuk Kim wrote:
> > >    Unable to handle kernel NULL pointer dereference at virtual address 000000000000001a
> > >    pc : f2fs_inplace_write_data+0x144/0x208
> > >    lr : f2fs_inplace_write_data+0x134/0x208
> > >    Call trace:
> > >     f2fs_inplace_write_data+0x144/0x208
> > >     f2fs_do_write_data_page+0x270/0x770
> > >     f2fs_write_single_data_page+0x47c/0x830
> > >     __f2fs_write_data_pages+0x444/0x98c
> > >     f2fs_write_data_pages.llvm.16514453770497736882+0x2c/0x38
> > >     do_writepages+0x58/0x118
> > >     __writeback_single_inode+0x44/0x300
> > >     writeback_sb_inodes+0x4b8/0x9c8
> > >     wb_writeback+0x148/0x42c
> > >     wb_do_writeback+0xc8/0x390
> > >     wb_workfn+0xb0/0x2f4
> > >     process_one_work+0x1fc/0x444
> > >     worker_thread+0x268/0x4b4
> > >     kthread+0x13c/0x158
> > >     ret_from_fork+0x10/0x18
> > >
> > > Fixes: 955772787667 ("f2fs: drop inplace IO if fs status is abnormal")
> >
> > My bad, thanks for fixing this.
> >
> > > Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> > > ---
> > >    fs/f2fs/segment.c | 8 +++++---
> > >    1 file changed, 5 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > > index c605415840b5..ae875557d693 100644
> > > --- a/fs/f2fs/segment.c
> > > +++ b/fs/f2fs/segment.c
> > > @@ -3577,9 +3577,11 @@ int f2fs_inplace_write_data(struct f2fs_io_info *fio)
> > >    	if (fio->bio) {
> > >    		struct bio *bio = *(fio->bio);
> > > -		bio->bi_status = BLK_STS_IOERR;
> > > -		bio_endio(bio);
> > > -		fio->bio = NULL;
> > > +		if (bio) {
> > > +			bio->bi_status = BLK_STS_IOERR;
> > > +			bio_endio(bio);
> > > +			fio->bio = NULL;
> >
> > fio->bio points a bio assigned in writepages(), so it should reset
> > that bio to NULL by *(fio->bio) = NULL.
>
> Good timing. I hit other kernel panic, and it seems this is the root cause.
> Let me give it a try. :)
>
> --- v2 ---
>
>   Unable to handle kernel NULL pointer dereference at virtual address 000000000000001a
>   pc : f2fs_inplace_write_data+0x144/0x208
>   lr : f2fs_inplace_write_data+0x134/0x208
>   Call trace:
>    f2fs_inplace_write_data+0x144/0x208
>    f2fs_do_write_data_page+0x270/0x770
>    f2fs_write_single_data_page+0x47c/0x830
>    __f2fs_write_data_pages+0x444/0x98c
>    f2fs_write_data_pages.llvm.16514453770497736882+0x2c/0x38
>    do_writepages+0x58/0x118
>    __writeback_single_inode+0x44/0x300
>    writeback_sb_inodes+0x4b8/0x9c8
>    wb_writeback+0x148/0x42c
>    wb_do_writeback+0xc8/0x390
>    wb_workfn+0xb0/0x2f4
>    process_one_work+0x1fc/0x444
>    worker_thread+0x268/0x4b4
>    kthread+0x13c/0x158
>    ret_from_fork+0x10/0x18
>
> Fixes: 955772787667 ("f2fs: drop inplace IO if fs status is abnormal")
> Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>

Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx>

Thanks,