Ticket History #6534: getaddrinfo in src/util/support/fake-addrinfo.c causes leak

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MadPartners LTD

System: Linux fever 2.6.30 #2 SMP Thu Jun 18 19:35:55 CEST 2009 i686 GNU/Linux


The function whose name was given in the synopsis contains a workaround
for a history problem with the glibc getaddrinfo:

Linux libc version 6 (libc-2.2.4.so on Debian) is broken.

[...]

The glibc 2.2.5 sources indicate that the canonical name is
*not* allocated separately, it's just some extra storage tacked
on the end of the addrinfo structure. So, let's try this
approach: If getaddrinfo sets ai_canonname, we'll replace the
*first* one with allocated storage,

This issue was fixed by Ulrich Drepper on 2004/08/17, cf

http://sourceware.org/git/?p=glibc.git;a=commit;f=ChangeLog;h=b93437642453ab93f7da79a15ca29cc66048e828

which implies that the ai_canonname-member has been allocated via strdup
at least since glibc release 2.3.4. The workaround mentionedc above overwrites
this allocated name with a newly allocated one, causing a memory leak.
use krb5_sname_to_princiapal
A somewhat crude way to fix this issues is provided by the patch below
(the warning is there because I didn't find the patchlevel anywhere in
the glibc includes, but need this for 2.3.6)

diff -pru krb5-1.7.orig/src/util/support/fake-addrinfo.c krb5-1.7/src/util/support/fake-addrinfo.c
--- krb5-1.7.orig/src/util/support/fake-addrinfo.c 2008-12-01 18:09:59.000000000 +0100
+++ krb5-1.7/src/util/support/fake-addrinfo.c 2009-07-21 19:19:16.000000000 +0200
@@ -140,7 +140,13 @@ extern /*@dependent@*/ char *gai_strerro
#endif

#if defined (__linux__) && defined(HAVE_GETADDRINFO)
+#ifdef __GLIBC_MINOR__
+#if __GLIBC_MINOR__ < 3
# define COPY_FIRST_CANONNAME
+#elif __GLIBC_MINOR__ == 3
+#warning GLIBC 2.3 < 2.3.4 needs COPY_FIRST_CANONNAME
+#endif
+#endif
#endif

#ifdef _AIX

I started trying to implement my idea and decided it was too much work,
with too much potential for bugginess, for a piece of code which is only
going to work around old buggy glibc versions. So I'm just going to
take your patch and adjust the comments a bit. Thanks again.

pull up r22643 from trunk

------------------------------------------------------------------------
r22643 | ghudson | 2009-08-28 12:00:54 -0400 (Fri, 28 Aug 2009) | 7 lines

ticket: 6534

Disable the COPY_FIRST_CANONNAME workaround on Linux glibc 2.4 and
later, since it leaks memory on fixed glibc versions. We will still
leak memory on glibc 2.3.4 through 2.3.6 (e.g. RHEL 4) but that's
harder to detect.

https://github.com/krb5/krb5/commit/98f0a65646833156bf86112ddf7ca02c0cd3447f
Commit By: tlyu
Revision: 23630
Changed Files:
U branches/krb5-1-7/src/util/support/fake-addrinfo.c