Re: Syslog bug

[Alex Kost <alezost@gmail.com>]

Ludovic Courtès (2015-04-01 22:51 +0300) wrote:

> Alex Kost <alezost@gmail.com> skribis:
>
>> Wow, I admire how deep you dig!  Your patch does some funny thing, it
>> "moves" corruption to another place.  Here is the output:
>>
>> # ./syslogd --debug --rcfile /tmp/syslog-with-leading-spaces.conf
>> init
>> cfline(*.alert;auth.notice;authpriv.none       /dev/console
>> sole)
>
> Oops, indeed, I had it too but hadn’t noticed.  :-)
>
> This is because the bcopy call didn’t copy the trailing zero, which is
> fixed by adding “+ 1”:
>
>
> diff --git a/src/syslogd.c b/src/syslogd.c
> index 7af10f3..aaf02a4 100644
> --- a/src/syslogd.c
> +++ b/src/syslogd.c
> @@ -1971,7 +1971,7 @@ load_conffile (const char *filename, struct filed **nextp)
>        if (*p == '\0' || *p == '#')
>  	continue;
>  
> -      strcpy (cline, p);
> +      bcopy (p, cline, strlen (p) + 1);
>  
>        /* Cut the trailing spaces.  */
>        for (p = strchr (cline, '\0'); isspace (*--p);)

OK, btw the manual (info "(libc) Copying and Concatenation") says
'bcopy' «is a partially obsolete alternative for 'memmove'».

>> --- a/src/syslogd.c
>> +++ b/src/syslogd.c
>> @@ -1971,7 +1971,7 @@ load_conffile (const char *filename, struct filed **nextp)
>>        if (*p == '\0' || *p == '#')
>>  	continue;
>>  
>> -      strcpy (cline, p);
>> +      strncpy (cline, p, strlen (cline));
>
> I guess this worked by chance: it does not copy the trailing zero, and
> it doesn’t address the overlapping-memory-regions issue.

By chance?  I thought it's reliable as it would fill the redundant part
of 'cline' (the rest part after copying 'p') with null characters.

>> A side note: compilation of inetutils failed for me complaining about
>> missing "help2man".  It finished successfully after I had added
>> "help2man" to native-inputs.
>
> That’s because the patch modifies the source of an executable for which
> a man page is generated.

Ah, thanks for the explanation.

> Thanks for your feedback!  I’ll report the issue upstream.

Great, thank you!

-- 
Alex