[v2,5/6] printk: insert newline in devkmsg_read()

Message ID 1405606151-19875-6-git-send-email-elder@linaro.org
State New
Headers show

Commit Message

Alex Elder July 17, 2014, 2:09 p.m.
If a log record has LOG_PREFIX set, its predecessor record should be
terminated if it was marked LOG_CONT.  In devkmsg_read(), this
condition was being ignored, which would lead to such records
showing up combined when reading /dev/kmsg.  Fix this oversight.

Reported-by: Petr Mládek <pmladek@suse.cz>
Signed-off-by: Alex Elder <elder@linaro.org>
---
 kernel/printk/printk.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Comments

Petr Mladek July 18, 2014, 11:45 a.m. | #1
On Thu 2014-07-17 09:09:10, Alex Elder wrote:
> If a log record has LOG_PREFIX set, its predecessor record should be
> terminated if it was marked LOG_CONT.  In devkmsg_read(), this
> condition was being ignored, which would lead to such records
> showing up combined when reading /dev/kmsg.  Fix this oversight.
>
> Reported-by: Petr Mládek <pmladek@suse.cz>
> Signed-off-by: Alex Elder <elder@linaro.org>
> ---
>  kernel/printk/printk.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index e5ee1cb..3174ba9 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -575,6 +575,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
>  	char cont;
>  	size_t len;
>  	ssize_t ret;
> +	bool insert_newline;
>  
>  	if (!user)
>  		return -EBADF;
> @@ -626,7 +627,10 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
>  	else
>  		cont = '-';
>  
> -	len = sprintf(user->buf, "%u,%llu,%llu,%c;",
> +	/* Insert a newline if we're terminating the previous record
> early */

More correct description would be:

	/* Insert a newline if the previous line was not terminated properly */

> +	insert_newline = (user->prev & LOG_CONT) && (msg->flags & LOG_PREFIX);
> +	len = sprintf(user->buf, "%s%u,%llu,%llu,%c;",
> +		      insert_newline ? "\n" : "",
>  		      (msg->facility << 3) | msg->level,
>  		      user->seq, ts_usec, cont);
>  	user->prev = msg->flags;

Please, do similar change also in msg_print_text() that would fix also
syslog(). Note that syslog is the place where we stopped to disable
prefix when there was continuous line before.

Best Regards.
Petr
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Alex Elder July 18, 2014, 2:02 p.m. | #2
On 07/18/2014 06:45 AM, Petr Mládek wrote:
> On Thu 2014-07-17 09:09:10, Alex Elder wrote:
>> If a log record has LOG_PREFIX set, its predecessor record should be
>> terminated if it was marked LOG_CONT.  In devkmsg_read(), this
>> condition was being ignored, which would lead to such records
>> showing up combined when reading /dev/kmsg.  Fix this oversight.
>>
>> Reported-by: Petr Mládek <pmladek@suse.cz>
>> Signed-off-by: Alex Elder <elder@linaro.org>
>> ---
>>  kernel/printk/printk.c | 6 +++++-
>>  1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
>> index e5ee1cb..3174ba9 100644
>> --- a/kernel/printk/printk.c
>> +++ b/kernel/printk/printk.c
>> @@ -575,6 +575,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
>>  	char cont;
>>  	size_t len;
>>  	ssize_t ret;
>> +	bool insert_newline;
>>  
>>  	if (!user)
>>  		return -EBADF;
>> @@ -626,7 +627,10 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
>>  	else
>>  		cont = '-';
>>  
>> -	len = sprintf(user->buf, "%u,%llu,%llu,%c;",
>> +	/* Insert a newline if we're terminating the previous record
>> early */
> 
> More correct description would be:
> 
> 	/* Insert a newline if the previous line was not terminated properly */

I will change it as you suggest.

> 
>> +	insert_newline = (user->prev & LOG_CONT) && (msg->flags & LOG_PREFIX);
>> +	len = sprintf(user->buf, "%s%u,%llu,%llu,%c;",
>> +		      insert_newline ? "\n" : "",
>>  		      (msg->facility << 3) | msg->level,
>>  		      user->seq, ts_usec, cont);
>>  	user->prev = msg->flags;
> 
> Please, do similar change also in msg_print_text() that would fix also
> syslog(). Note that syslog is the place where we stopped to disable
> prefix when there was continuous line before.

I will do this, as you will see in v3 which I plan to post in a
few hours.  (Note that this touches a spot where I have yet another
minor bug fix that I have not yet posted...  Oh well.)

					-Alex

> Best Regards.
> Petr
> 

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diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index e5ee1cb..3174ba9 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -575,6 +575,7 @@  static ssize_t devkmsg_read(struct file *file, char __user *buf,
 	char cont;
 	size_t len;
 	ssize_t ret;
+	bool insert_newline;
 
 	if (!user)
 		return -EBADF;
@@ -626,7 +627,10 @@  static ssize_t devkmsg_read(struct file *file, char __user *buf,
 	else
 		cont = '-';
 
-	len = sprintf(user->buf, "%u,%llu,%llu,%c;",
+	/* Insert a newline if we're terminating the previous record early */
+	insert_newline = (user->prev & LOG_CONT) && (msg->flags & LOG_PREFIX);
+	len = sprintf(user->buf, "%s%u,%llu,%llu,%c;",
+		      insert_newline ? "\n" : "",
 		      (msg->facility << 3) | msg->level,
 		      user->seq, ts_usec, cont);
 	user->prev = msg->flags;