linux-kernel - Re: [PATCH] soc: qcom: cmd-db: Drop NUL bytes from debugfs output

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Date:   Wed, 21 Jun 2023 01:27:24 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Stephen Boyd <swboyd@...omium.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] soc: qcom: cmd-db: Drop NUL bytes from debugfs output

On 20.06.2023 23:37, Bjorn Andersson wrote:
> The debugfs dump of Command DB relies uses %*pEp to print the resource
> identifiers, with escaping of non-printable characters.
> But p (ESCAPE_NP) does not escape NUL characters, so for identifiers
> less than 8 bytes in length the output will retain these.
> 
> This does not cause an issue while looking at the dump in the terminal
> (no known complaints at least), but when programmatically consuming the
> debugfs output the extra characters are unwanted.
> 
> Change the fixed 8-byte sizeof() to a dynamic strnlen() to avoid
> printing these NUL characters.
> 
> Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
> ---
Reviewed-by: Konrad Dybcio <konrad.dybcio@...aro.org>

Konrad
>  drivers/soc/qcom/cmd-db.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/soc/qcom/cmd-db.c b/drivers/soc/qcom/cmd-db.c
> index 33856abd560c..34c40368d5b5 100644
> --- a/drivers/soc/qcom/cmd-db.c
> +++ b/drivers/soc/qcom/cmd-db.c
> @@ -284,7 +284,7 @@ static int cmd_db_debugfs_dump(struct seq_file *seq, void *p)
>  		ent = rsc_to_entry_header(rsc);
>  		for (j = 0; j < le16_to_cpu(rsc->cnt); j++, ent++) {
>  			seq_printf(seq, "0x%05x: %*pEp", le32_to_cpu(ent->addr),
> -				   (int)sizeof(ent->id), ent->id);
> +				   (int)strnlen(ent->id, sizeof(ent->id)), ent->id);
>  
>  			len = le16_to_cpu(ent->len);
>  			if (len) {