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

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Message-ID: <9df7d088-3580-122b-60a3-799ea665cfeb@huawei.com>
Date:   Tue, 11 May 2021 09:29:07 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>, <linux-kernel@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [f2fs-dev] [PATCH] f2fs: avoid null pointer access when handling
 IPU error

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@...nel.org>
> ---
>   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.

Thanks,

> +		}
>   	}
>   	return err;
>   }
>