RE: [PATCH v2] libselinux: clean up process file

[Roberts, William C]

> -----Original Message-----
> From: Stephen Smalley [mailto:s...@tycho.nsa.gov]
> Sent: Thursday, September 8, 2016 12:41 PM
> To: Roberts, William C <william.c.robe...@intel.com>; selinux@tycho.nsa.gov;
> seandroid-l...@tycho.nsa.gov; jwca...@tycho.nsa.gov
> Subject: Re: [PATCH v2] libselinux: clean up process file
> 
> On 09/08/2016 03:30 PM, Roberts, William C wrote:
> > <snip>
> >
> >>>> +        /* Append any given suffix */
> >>>> +        char *to = stpcpy(&current[current_size], ".");
> >>>
> >>> Simpler as:
> >>>   char *to = current + current_size;
> >>>   *to++ = '.';
> >>
> >> I don't think this is simpler, but I'll do it.
> >
> > Doing that as is gets us this:
> > ==26050== Conditional jump or move depends on uninitialised value(s)
> > ==26050==    at 0x4C2DD9A: strcat (in /usr/lib/valgrind/vgpreload_memcheck-
> amd64-linux.so)
> > ==26050==    by 0x4E4B6D8: rolling_append (label_file.c:429)
> > ==26050==    by 0x4E4B8A3: open_file (label_file.c:472)
> > ==26050==    by 0x4E4BAC6: process_file (label_file.c:519)
> > ==26050==    by 0x4E4BE6D: init (label_file.c:582)
> > ==26050==    by 0x4E4D02B: selabel_file_init (label_file.c:965)
> > ==26050==    by 0x4E481F5: selabel_open (label.c:340)
> > ==26050==    by 0x4E513E0: matchpathcon_init_prefix (matchpathcon.c:322)
> > ==26050==    by 0x4E51725: matchpathcon (matchpathcon.c:413)
> > ==26050==    by 0x400D86: printmatchpathcon (matchpathcon.c:26)
> > ==26050==    by 0x40141F: main (matchpathcon.c:196)
> >
> > Because strcat() needs to fastforward to the null byte, this would
> > need to change to an strcpy.
> 
> Yes, sorry - switch the strcat() to strcpy() too.  Simpler and more 
> efficient, and if
> you had to append further components, you could use
> stpcpy() rather than strcpy() each time until the last one.
> 
FYI: That change actually dropped off aprox 100 bytes on the obj code.


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