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Date: Fri, 19 Jul 2013 12:07:02 +0800
From: Chen Gang <gang.chen@...anux.com>
To: Al Viro <viro@...IV.linux.org.uk>
CC: George Spelvin <linux@...izon.com>, reiserfs-devel@...r.kernel.org,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] reiserfs: check/extend buffer length for printing functions
On 07/18/2013 04:18 PM, Chen Gang wrote:
> On 07/18/2013 03:54 PM, Chen Gang wrote:
>> On 07/18/2013 03:43 PM, Al Viro wrote:
>>> On Thu, Jul 18, 2013 at 03:29:17PM +0800, Chen Gang wrote:
>>>>> On 07/18/2013 12:28 PM, Chen Gang wrote:
>>>>>>>
>>>>>>>>> strcpy(fmt1, fmt);
>>>>>>>>> @@ -199,46 +214,51 @@ static void prepare_error_buf(const char *fmt, va_list args)
>>>>>>>>> while ((k = is_there_reiserfs_struct(fmt1, &what)) != NULL) {
>>>>>>>>> *k = 0;
>>>>>>>>>
>>>>>>>>> - p += vsprintf(p, fmt1, args);
>>>>>>>>> + p += vsnprintf(p, left, fmt1, args);
>>>>>
>>>>> At least, need use vscnprintf() instead of vsnprintf(), since we need
>>>>> the real written length return.
>>> n = vsnprintf(p, left, ....);
>>> left -= n;
>>> if (left <= 0) /* overflow */
>>> break; /* or whatever's suitable here */
>>> p += n;
>>>
>>>
>>
>> Yeah, it is really a better fix. :-)
>>
>>
>> And now I am just testing, and find another issue about it, I am just
>> analyzing it it.
>
>
> even only change vsprintf() to vsnprintf(), it will report '<7' !!
>
I finish analyzing it, it is not an issue.
'<7>' or '<5>' ... is the level, '<7>' is 'KERN_DEBUG', '<5>' is
'KERN_NOTICE' ...
For system log, the kernel always print level before time stamp, but
when we type command 'dmesg', it will skip them at the head of a line
(also skip the empty line).
It is implemented in "kernel/printk.c", below.
887 static size_t print_prefix(const struct log *msg, bool syslog, char *buf)
888 {
889 size_t len = 0;
890 unsigned int prefix = (msg->facility << 3) | msg->level;
891
892 if (syslog) {
893 if (buf) {
894 len += sprintf(buf, "<%u>", prefix);
895 } else {
896 len += 3;
897 if (prefix > 999)
898 len += 3;
899 else if (prefix > 99)
900 len += 2;
901 else if (prefix > 9)
902 len++;
903 }
904 }
905
906 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
907 return len;
908 }
909
When a string truncated by force (may without '\n'). It may print level
and time stamp not at the head of the line, which can not be skipped by
dmesg.
That is the reason why we can not see it.
We can try to modify the print_prefix() in "kernel/printk.c" to test
the result which I provide above.
e.g. append addition information after the time stamp to be sure that this function is really affect to all lines which command 'dmesg' displays.
e.g. use "\n<%u>" instead of "<%u>" and dummy 'syslog', to know dmesg will skip the level at the head of the line, and also skip the empty line.
And next, I will send patch v2 for this patch.
Welcome any additional suggestions, checking, or completions.
:-)
Thanks.
> ----------------------------diff begin---------------------------------
>
> diff --git a/fs/reiserfs/prints.c b/fs/reiserfs/prints.c
> index c0b1112..9dd79be 100644
> --- a/fs/reiserfs/prints.c
> +++ b/fs/reiserfs/prints.c
> @@ -238,7 +238,8 @@ static void prepare_error_buf(const char *fmt, va_list args)
> p += strlen(p);
> fmt1 = k + 2;
> }
> - vsprintf(p, fmt1, args);
> +
> + vsnprintf(p, 13, fmt1, args);
> spin_unlock(&error_lock);
>
> }
>
> ----------------------------diff end-----------------------------------
>
> This patch seems related with this new issue. So After I finish
> analyzing it (get root cause), then send the patch v2 for this patch.
>
>
> Thanks.
>
>>
>> For next-20130717, let reiserfs build-in, when "mount /dev/sda11
>> /mnt/sda11" (assume sda11 is reiserfs filesystem).
>>
>> I modify the code like this (just only use vsnprintf instead of vsprintf):
>>
>> --------------------------diff begin------------------------------
>>
>> diff --git a/fs/reiserfs/prints.c b/fs/reiserfs/prints.c
>> index c0b1112..3a38a62 100644
>> --- a/fs/reiserfs/prints.c
>> +++ b/fs/reiserfs/prints.c
>> @@ -10,7 +10,7 @@
>>
>> #include <stdarg.h>
>>
>> -static char error_buf[1024];
>> +static char error_buf[13];
>> static char fmt_buf[1024];
>> static char off_buf[80];
>>
>> @@ -195,7 +195,7 @@ static void prepare_error_buf(const char *fmt, va_list args)
>> spin_lock(&error_lock);
>>
>> strcpy(fmt1, fmt);
>> -
>> +#if 0
>> while ((k = is_there_reiserfs_struct(fmt1, &what)) != NULL) {
>> *k = 0;
>>
>> @@ -238,7 +238,8 @@ static void prepare_error_buf(const char *fmt, va_list args)
>> p += strlen(p);
>> fmt1 = k + 2;
>> }
>> - vsprintf(p, fmt1, args);
>> +#endif
>> + vsnprintf(p, 13, fmt1, args);
>> spin_unlock(&error_lock);
>>
>> }
>>
>> --------------------------diff end--------------------------------
>>
>>
>> The output has '<7>':
>>
>> [root@...p122 ~]# dmesg
>> [ 38.797073] REISERFS (device sda11): found reiser
>> [ 38.797089] REISERFS warning (device sda11): reiserfs_fill_super: CONFIG_REISE
>> [ 38.797095] REISERFS warning (device sda11): reiserfs_fill_super: - it is slow
>> [ 38.797098] REISERFS (device sda11): using orderereiserfs: using flush barriers
>> [ 38.800507] REISERFS (device sda11): journal para
>> [ 38.801158] REISERFS (device sda11): checking tra<7>[ 38.801165] REISERFS debug (device sda11): journal-1153
>> [ 38.801405] REISERFS debug (device sda11): journal-1206
>> [ 38.801410] REISERFS debug (device sda11): journal-1299
>> [ 38.817621] REISERFS (device sda11): Using r5 has
>> [ 38.817906] SELinux: initialized (dev sda11, type reiserfs), uses genfs_contexts
>>
>>
>>
>> Welcome any suggestions or completions.
>>
>> Thanks.
>>
>
>
--
Chen Gang
--
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