Re: [PATCH v2] mtd: ubi: eba.c: fix return value overwrite issue in try_write_vid_and_data()

Zhihao Cheng
2023-03-29T01:14:37Z

> The commit 2d78aee426d8 ("UBI: simplify LEB write and atomic LEB change code")
> adds helper function, try_write_vid_and_data(), to simplify the code, but this
> helper function has bug, it will return 0 (success) when ubi_io_write_vid_hdr()
> or the ubi_io_write_data() return error number (-EIO, etc), because the return
> value of ubi_wl_put_peb() will overwrite the original return value.
>
> This issue will cause unexpected data loss issue, because the caller of this
> function and UBIFS willn't know the data is lost.
>
> Fixes: 2d78aee426d8 ("UBI: simplify LEB write and atomic LEB change code")
>
> Signed-off-by: Wang YanQing <udknight@gmail.com>
> ---
> Changes v1-v2:
> 1: add error code in warning message, suggested by Zhihao Cheng
>
> drivers/mtd/ubi/eba.c | 19 ++++++++++++++-----
> 1 file changed, 14 insertions(+), 5 deletions(-)
>

Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>

> diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
> index 09c408c..4e1d807 100644
> --- a/drivers/mtd/ubi/eba.c
> +++ b/drivers/mtd/ubi/eba.c
> @@ -946,7 +946,7 @@ static int try_write_vid_and_data(struct ubi_volume *vol, int lnum,
> int offset, int len)
> {
> struct ubi_device *ubi = vol->ubi;
> - int pnum, opnum, err, vol_id = vol->vol_id;
> + int pnum, opnum, err, err2, vol_id = vol->vol_id;
>
> pnum = ubi_wl_get_peb(ubi);
> if (pnum < 0) {
> @@ -981,10 +981,19 @@ static int try_write_vid_and_data(struct ubi_volume *vol, int lnum,
> out_put:
> up_read(&ubi->fm_eba_sem);
>
> - if (err && pnum >= 0)
> - err = ubi_wl_put_peb(ubi, vol_id, lnum, pnum, 1);
> - else if (!err && opnum >= 0)
> - err = ubi_wl_put_peb(ubi, vol_id, lnum, opnum, 0);
> + if (err && pnum >= 0) {
> + err2 = ubi_wl_put_peb(ubi, vol_id, lnum, pnum, 1);
> + if (err2) {
> + ubi_warn(ubi, "failed to return physical eraseblock %d, error %d",
> + pnum, err2);
> + }
> + } else if (!err && opnum >= 0) {
> + err2 = ubi_wl_put_peb(ubi, vol_id, lnum, opnum, 0);
> + if (err2) {
> + ubi_warn(ubi, "failed to return physical eraseblock %d, error %d",
> + opnum, err2);
> + }
> + }
>
> return err;
> }
>