linux-kernel - RE: [PATCH] scsi: ufs: Leave space for '\0' in utf8 desc string

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Message-ID: <DM6PR04MB6575C45CF299649DF41FD963FCD6A@DM6PR04MB6575.namprd04.prod.outlook.com>
Date:   Tue, 17 Oct 2023 19:20:48 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Daniel Mentz <danielmentz@...gle.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Tomas Winkler <tomas.winkler@...el.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Mars Cheng <marscheng@...gle.com>,
        Bart Van Assche <bvanassche@....org>,
        Yen-lin Lai <yenlinlai@...gle.com>
Subject: RE: [PATCH] scsi: ufs: Leave space for '\0' in utf8 desc string

> utf16s_to_utf8s does not NULL terminate the output string. For us to be able
> to add a NULL character when utf16s_to_utf8s returns, we need to make
> sure that there is space for such NULL character at the end of the output
> buffer. We can achieve this by passing an output buffer size to
> utf16s_to_utf8s that is one character less than what we allocated.
> 
> Other call sites of utf16s_to_utf8s appear to be using the same technique
> where they artificially reduce the buffer size by one to leave space for a
> NULL character or line feed character.
> 
> Fixes: 4b828fe156a6 ("scsi: ufs: revamp string descriptor reading")
I think this code goes back to commit b573d484e4ff (scsi: ufs: add support to read device and string descriptors)

Reviewed-by: Avri Altman <avri.altman@....com>

> Reviewed-by: Mars Cheng <marscheng@...gle.com>
> Reviewed-by: Bart Van Assche <bvanassche@....org>
> Reviewed-by: Yen-lin Lai <yenlinlai@...gle.com>
> Signed-off-by: Daniel Mentz <danielmentz@...gle.com>
> ---
>  drivers/ufs/core/ufshcd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c index
> 8382e8cfa414..5767642982c1 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -3632,7 +3632,7 @@ int ufshcd_read_string_desc(struct ufs_hba *hba,
> u8 desc_index,
>                  */
>                 ret = utf16s_to_utf8s(uc_str->uc,
>                                       uc_str->len - QUERY_DESC_HDR_SIZE,
> -                                     UTF16_BIG_ENDIAN, str, ascii_len);
> +                                     UTF16_BIG_ENDIAN, str, ascii_len -
> + 1);
> 
>                 /* replace non-printable or non-ASCII characters with spaces */
>                 for (i = 0; i < ret; i++)
> --
> 2.42.0.655.g421f12c284-goog