[PATCH] BROKEN_STRNDUP and BROKEN_STRNLEN and AIX

[Andrew Bartlett]

On Wed, 2013-05-22 at 11:18 +0300, Alexander Bokovoy wrote:
> 
> Hi,
> 
> 
> On Wed, May 22, 2013 at 11:11 AM, Andrew Bartlett <abartlet at samba.org>
> wrote:
>         On Wed, 2013-05-22 at 11:05 +0300, Alexander Bokovoy wrote:
>         > Hi,
>         >
>         >
>         > On Wed, May 22, 2013 at 10:39 AM, Andrew Bartlett
>         <abartlet at samba.org>
>         > wrote:
>         >         Simo and Christian,
>         >
>         >         I'm wondering if either of you know more about the
>         allegation
>         >         that
>         >         strndup and strnlen are broken on AIX?
>         >
>         >         This is one of the very few outstanding config.h
>         differences
>         >         I'm tracking in
>         >         https://bugzilla.samba.org/show_bug.cgi?id=8969
>         >
>         >         It appears to be forced on for all AIX hosts:
>         >
>         >         commit 804cfb20a067b4b687089dc72a8271b3abf20f31
>         >         Author: Simo Sorce <idra at samba.org>
>         >         Date:   Wed Aug 25 14:24:16 2004 +0000
>         >
>         >             r2070: Let's try to overload srnlen and strndup
>         for AIX
>         >         where they are natly broken.
>         >             (This used to be commit
>         >         98feb3318f54bb48ce56fc8f4721fec4967b9dd9)
>         >
>         >         diff --git a/source3/configure.in
>         b/source3/configure.in
>         >         index d35e89c..4329665 100644
>         >         --- a/source3/configure.in
>         >         +++ b/source3/configure.in
>         >         @@ -1206,6 +1206,8 @@ if test "$enable_shared" =
>         "yes"; then
>         >                                 fi
>         >
>         >
>         >         AC_DEFINE(STAT_ST_BLOCKSIZE,DEV_BSIZE,[The size of a
>         block])
>         >         +
>         AC_DEFINE(BROKEN_STRNLEN,1,[Does
>         >         strnlen work correctly])
>         >         +
>         AC_DEFINE(BROKEN_STRNDUP,1,[Does
>         >         strndup work correctly])
>         >                                 ;;
>         >                         *hpux*) AC_DEFINE(HPUX,1,[Whether
>         the host os
>         >         is HPUX])
>         >                                 SHLIBEXT="sl"
>         >
>         >         Before I simply do the same in waf (probably in
>         libreplace),
>         >         do either
>         >         of you know more of the background here, such as
>         does this
>         >         apply to all
>         >         AIX versions, or is it possible to test for it less
>         bluntly?
>         > This discussion (which refers to our bug #1097) clarifies
>         the issue:
>         >
>         http://stackoverflow.com/questions/2091460/strndup-call-is-currupting-stack-frames
>         >
>         >
>         > strndup() is broken at least on AIX 6.1:
>         > ".. Tracing through the instructions in strndup, it appears
>         that it
>         > mallocs a buffer that is just large enough to handle the
>         string in s
>         > plus a NULL terminator. However, it will always copy n
>         characters to
>         > the new buffer, padding with zeros if necessary, causing a
>         buffer
>         > overflow if strlen(s) < n."
>         
>         
>         The revised attached patch tries to put some of this
>         background into the
>         code.
> I wonder if we could simply run the reproducer and if that fails
> outlaw strndup()?
> 
> The reproducer is available in this
> answer:http://stackoverflow.com/a/12080251
> 
> Running it would preclude cross-compiling to AIX but that is not
> something we could do now anyway.

I don't think we can, as if we are lucky in our page boundaries and it
doesn't segfault during configure, it still may segfault later, and
segfaults during configure tend to cause alarms due to system global
segfault tracking (we had this happen with snprintf before). 

Andrew Bartlett

-- 
Andrew Bartlett                                http://samba.org/~abartlet/
Authentication Developer, Samba Team           http://samba.org