Re: [PATCH] printk: finalize records with trailing newlines

[Kefeng Wang]

On 2020/11/26 19:48, John Ogness wrote:
> Any record with a trailing newline (LOG_NEWLINE flag) cannot
> be continued because the newline has been stripped and will
> not be visible if the message is appended. This was already
> handled correctly when committing in log_output() but was
> not handled correctly when committing in log_store().
>
> Fixes: f5f022e53b87 ("printk: reimplement log_cont using record extension")
> Signed-off-by: John Ogness <john.ogness@xxxxxxxxxxxxx>
> ---
>   This is an important bugfix for continuous messages and should
>   be part of the 5.10 release.
>
>   If not applied, newlines will vanish when concatenating
>   continuous with trailing newlines.
Thanks for you quick fix.

Reported-and-tested-by:  Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>

>   kernel/printk/printk.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index fe64a49344bf..bc1e3b5a97bd 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -528,8 +528,8 @@ static int log_store(u32 caller_id, int facility, int level,
>   	if (dev_info)
>   		memcpy(&r.info->dev_info, dev_info, sizeof(r.info->dev_info));
>   
> -	/* insert message */
> -	if ((flags & LOG_CONT) || !(flags & LOG_NEWLINE))
> +	/* A message without a trailing newline can be continued. */
> +	if (!(flags & LOG_NEWLINE))
>   		prb_commit(&e);
>   	else
>   		prb_final_commit(&e);